Fire Safety Academy Wiki - User contributions [en]

Fire safety objectives

2026-11-02T18:39:27Z

Mark: Revise against the FSE wiki writing guidelines: attribution of the design process and wording after independent fact-check (revised by Claude Opus 5.5)

'''Fire safety objectives''' are the specific fire safety goals that a building or facility is meant to achieve.<ref name="Watts-5-136">Watts (2002), pp. 5-136–5-137.</ref> Typical examples are life safety, property protection, continuity of operations, environmental protection and the preservation of heritage.<ref name="Watts-5-136" /> They state what a fire safety design has to achieve, and so explain why fire safety measures are taken at all.<ref name="VR-1">Van Rossum (2027), §1.</ref> Some objectives are set by law, such as protecting the occupants and preventing fire spread between buildings. Others are chosen by the client or by other stakeholders, for example an insurer.<ref name="IFEG-1-2-7">National Research Council of Canada et al. (2005), pp. 1.2-7–1.2-8.</ref> [[Fire safety engineering]] can itself be defined as applying all fire-related knowledge to achieve the relevant fire safety goals of a project, so the objectives come first.<ref name="VR-1-1">Van Rossum (2027), §1.1.</ref>

Objectives are normally written in general words, such as safeguarding people from an unacceptable risk of injury or illness caused by fire.<ref name="CVM2-37">Ministry of Business, Innovation and Employment (2025b), p. 37.</ref> Before a design can be checked, they are refined into numerical performance criteria, for example a maximum temperature or a limit on fire spread.<ref name="Notarianni-5-52">Notarianni (2002), pp. 5-52–5-53.</ref> Building regulations seldom state how safe is safe enough.<ref name="VR-1-2">Van Rossum (2027), §1.2.</ref><ref name="IFEG-NZ-0-2-5">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.2-5.</ref> In a performance-based design, the objectives and criteria are therefore agreed between the parties involved before the analysis starts.<ref name="IFEG-1-2-2">National Research Council of Canada et al. (2005), p. 1.2-2.</ref><ref name="IFEG-US-0-2-8">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-8.</ref>

== Goals, objectives and criteria ==

In the SFPE Handbook, a common hierarchy of fire safety decisions has five levels, although a particular application may have more or fewer. Objectives form the second level.<ref name="Watts-5-136" /> Above them is the fire safety policy that an organisation adopts to achieve security against fire and its effects. Below them come strategies, each of which contributes wholly or partly to the objectives. The lowest levels are attributes and survey items, which can be measured or estimated in a real building.<ref name="Watts-5-136" /> Broad aims such as fire prevention, fire control and occupant protection usually appear in the introductory sections of building codes and fire safety laws.<ref name="Watts-5-136" />

The terms are not used consistently, and an objective is sometimes simply called a goal. The International Fire Engineering Guidelines (2005) define an objective as the desired overall safety outcome, expressed in qualitative terms.<ref name="IFEG-US-0-5-4">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.5-4–0.5-5.</ref> A functional statement is more specific and states what the building, its systems or its occupants must achieve for an objective to be met. A performance requirement gives the criteria, in engineering terms, by which a trial design is judged.<ref name="IFEG-US-0-5-4" /> In the SFPE Handbook, stakeholders first identify broad goals, such as protecting people and property. These goals are then refined into objectives that can be quantified in engineering terms.<ref name="Notarianni-5-52" />

A simple chain shows how the levels connect, starting from the goal of protecting the occupants. A matching objective may be to keep the gas concentrations in a corridor tenable. The performance criterion then sets the numerical limit against which the expected performance of the design is compared.<ref name="Notarianni-5-52" /> New Zealand's Building Code uses the same ladder of objectives, functional requirements and performance criteria.<ref name="CVM2-2">Ministry of Business, Innovation and Employment (2025b), p. 2.</ref> A report for the US Nuclear Regulatory Commission notes that performance-based designs state their goals explicitly, whereas prescriptive requirements contain them only implicitly.<ref name="NUREG-1-9">Iqbal and Salley (2004), p. 1-9.</ref>

Objectives can be secured in two ways. In a rule-based approach, the design follows predefined rules and limit values, such as legislation, the conditions of an insurer or company rules. Such rules are generic and inflexible, and only partly tailored to the building, its users and its surroundings. In a risk-based or goal-based approach, fire safety is assessed for the specific project, so that more factors can be weighed together. In the Netherlands, such an alternative to the Dutch Buildings Decree (Bbl) is called equivalence. Article 4.7 of the Environment and Planning Act (Omgevingswet) allows it on condition that it achieves at least the same level of fire safety as the prescribed measure that it replaces.<ref name="VR-1" />

== Typical objectives ==

Most fire safety objectives trace back, directly or indirectly, to the protection of people.<ref name="HallAhrens-5-74">Hall and Ahrens (2002), p. 5-74.</ref> The safety of the people in a building when a fire breaks out is one of the most important objectives. Dying in a fire is also perceived as worse than dying in a car accident.<ref name="VR-7">Van Rossum (2027), §7.</ref> Keeping every occupied area completely free of fire effects would be a very conservative and generally unachievable objective. An engineering analysis therefore has to consider what happens to the occupants: how many there are, where they are, how they act and what they can do.<ref name="HallAhrens-5-74" />

Building codes commonly also aim to facilitate the work of the emergency services. Property objectives can concern the building itself, its contents and equipment, or neighbouring buildings. Other common objectives are business continuity and financial viability, corporate and public image, and community interests and infrastructure. Some projects also aim to protect heritage in older or significant buildings, or to limit the release of hazardous materials into the environment.<ref name="IFEG-1-2-7" /> The book ''Introduction to Fire Safety Engineering'' adds limiting the impact of a fire on society. It notes that its own list is an arbitrary and incomplete mix of public and private goals.<ref name="VR-1" />

It is not always clear how something is valued or how its loss should be described.<ref name="Meacham-5-153">Meacham (2002), pp. 5-153–5-154.</ref> For life safety, some people draw the line simply between life and death. Others also count quality of life, pain and suffering, and rehabilitation after an injury.<ref name="Meacham-5-155">Meacham (2002), p. 5-155.</ref> For property, smoke and water damage should be considered as well as damage by heat. For business continuity, a loss of image and market share can follow long after the short-term losses of downtime.<ref name="Meacham-5-153" />

Outside ordinary buildings, the objectives can be quite different. For US nuclear power plants, the primary objectives of fire protection programmes are to minimise both the probability and the consequences of fire. Through defence in depth, these programmes are designed to give reasonable assurance that a fire will not prevent a safe shutdown and that radioactive releases are minimised.<ref name="NUREG-1-1">Iqbal and Salley (2004), p. 1-1.</ref> Defence in depth aims at a balance between preventing fires from starting, detecting and suppressing fires quickly, and limiting the consequences of a fire.<ref name="NUREG-F-20">Iqbal and Salley (2004), p. F-20.</ref>

== Objectives in building regulations ==

[[Building regulations]] set the public objectives that every building must meet, usually in broad words rather than in numbers.<ref name="VR-1-4">Van Rossum (2027), §1.4.</ref><ref name="ABCB-14">Australian Building Codes Board (2020b), p. 14.</ref> In the Netherlands, the explanatory notes to the Dutch Buildings Decree (Bbl) give two aims for its fire safety rules. These are preventing casualties, both injured and dead, and preventing a fire from spreading to another plot. Preserving the building and preventing damage to the environment, monuments or social facilities or interests are explicitly not objectives of the decree. The rules work these aims out in sub-goals, such as keeping the structure standing, limiting fire and smoke spread, and keeping escape and firefighting routes usable.<ref name="VR-1-2" />

In New Zealand, Verification Method C/VM2 (second edition, 2025) relates all its design scenarios to three fire objectives of the Building Code.<ref name="CVM2-7">Ministry of Business, Innovation and Employment (2025b), pp. 7–8.</ref> They are to safeguard people from an unacceptable risk of injury or illness caused by fire, and to protect other property from damage caused by fire. The third is to facilitate firefighting and rescue operations.<ref name="CVM2-58">Ministry of Business, Innovation and Employment (2025b), pp. 58–59.</ref> In Australia, the 2020 handbook to the Fire Safety Verification Method, written for the 2019 edition of the National Construction Code (NCC 2019), summarises the broad fire objectives of that code.<ref name="ABCB-2">Australian Building Codes Board (2020b), p. 2.</ref> They are life safety of occupants, protection of other property, facilities for firefighting and fire safety during construction. The protection of the building itself and its contents is addressed only to a limited extent for some building classes.<ref name="ABCB-27">Australian Building Codes Board (2020b), pp. 27–28.</ref>

The International Fire Engineering Guidelines describe two further systems as they were in 2005. The 2005 National Building Code of Canada was the first edition in an objective-based format, in which every provision serves at least one stated objective. Its objectives are worded as limiting the probability of undesirable situations, because a code cannot prevent them completely. The risk that remains after the code is complied with is regarded as the acceptable risk.<ref name="IFEG-CA-0-2-2">National Research Council of Canada et al. (2005), Part 0 (Canada), p. 0.2-2.</ref> For the United States, the guidelines note that choosing the intended level of performance is a value judgement that should ultimately be made by policy makers rather than by designers.<ref name="IFEG-US-0-2-6">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-6.</ref>

The overall level of safety is rarely stated in numbers.<ref name="ABCB-14" /> The Dutch rules do not lay down how many deaths and injuries are acceptable, or how large the risk of fire spread to a neighbouring plot may be. Their measurable limits apply to the measures instead, such as walking distances, minutes of fire resistance and compartment areas. These limits grew partly from consensus and partly from history, not from a quantified goal.<ref name="VR-1-2" /> The 2005 guidelines note that in New Zealand, too, the level of safety of the Building Code is not always stated explicitly, which can make its requirements hard to interpret.<ref name="IFEG-NZ-0-2-5" />

== Objectives of owners and other stakeholders ==

In a performance-based project, the objectives are agreed in the fire engineering brief (FEB), the process in which the stakeholders set down the basis of the analysis.<ref name="IFEG-1-2-2" /><ref name="IFEG-1-2-7" /> The International Fire Engineering Guidelines suggest first identifying the objectives of each stakeholder, which may differ. These are then divided into building regulatory, other regulatory and non-regulatory objectives. Other regulatory objectives come from laws on matters such as the environment, occupational health and safety, the fire services, dangerous goods and planning. Non-regulatory objectives are set by the client or other stakeholders, for example to limit damage to the structure, contents and equipment.<ref name="IFEG-1-2-7" />
[[File:fse-fire-safety-objectives-v1.svg|thumb|upright=1.5|alt=Building law, other law and stakeholders contribute distinct objectives to one project.|Fire-safety objectives arise from different requirements and stakeholder goals. Based on National Research Council of Canada et al. (2005), pp. 1.2-7–1.2-8.]]

Complying with the code and protecting an owner's assets are not the same thing. Some owners do not realise that code compliance can differ significantly from protecting their building, process, contents or other assets of value. Such differences matter when tolerable damage and acceptance criteria are chosen, so the interested and affected parties must be involved.<ref name="Meacham-5-155" /> For New Zealand, the 2005 guidelines explain that the Building Act 2004 does not require anyone to exceed the performance criteria of the Building Code, so doing so is the owner's choice.<ref name="IFEG-NZ-0-3-6">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-6.</ref>

Clients also have objectives that are not about fire but still affect fire safety. Examples are increased security, natural lighting, an open-plan layout, new materials, energy efficiency, flexibility for future uses and low life-cycle costs.<ref name="IFEG-1-2-7" /> In the New Zealand part of the guidelines, the fire engineer is responsible for ensuring that such objectives do not stop the design from meeting the fire requirements of the Building Code.<ref name="IFEG-NZ-0-3-3">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-3.</ref> The engineer should also explain to the client the effect of adopting further objectives or not, and decline instructions where the objectives are unacceptable.<ref name="IFEG-NZ-0-4-1">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.4-1.</ref> In Australia, the 2020 handbook likewise asks for client and end-user objectives to be identified early.<ref name="ABCB-22">Australian Building Codes Board (2020b), p. 22.</ref>

Stakeholders do not always value the same outcomes in the same way. Some people accept a higher risk to firefighters, who take on risk as part of their job, if this lowers the risk to the public, while others do not.<ref name="Notarianni-5-46">Notarianni (2002), p. 5-46.</ref> Stakeholders may want to protect historic features or to avoid business interruption, and those with different values may see these needs differently. The SFPE Handbook therefore advises identifying where value judgements enter a design and making these assumptions explicit.<ref name="Notarianni-5-52" />

== From objectives to acceptance criteria ==

Objectives are too broad to be checked directly, so [[Acceptance criteria|acceptance criteria]] are set for the analysis.<ref name="IFEG-CA-0-2-2" /> The criteria must suit the objectives, the performance requirements and the analysis methods. They must also be numerical, unless the analysis is qualitative, and realistic: zero risk is not an appropriate criterion.<ref name="IFEG-1-2-25">National Research Council of Canada et al. (2005), pp. 1.2-25–1.2-26.</ref> In the ten-step design process of the SFPE engineering guide, as tabulated in the SFPE Handbook, the scope, goals and objectives are defined before the performance criteria are developed. Design fire scenarios, candidate designs and their evaluation follow after that.<ref name="Notarianni-5-52" />

The guidelines give typical criteria for each general objective. Protecting occupants can be judged by the margin between the available and the required escape time, and by the smoke layer height. Other occupant criteria are the temperature and radiant heat of the hot layer, the smoke density and the carbon monoxide level. Facilitating the fire services can be judged by radiant heat, structural failure, water supply and resources at the fire scene. Protecting adjacent property uses the radiant heat from the fire and flame impingement, while limiting damage and keeping a business running use monetary loss, smoke release and corrosive gases. Environmental objectives use the toxicity of the fire gases, the containment of firefighting water and the expected risk to plants and animals.<ref name="IFEG-1-2-25" />
[[File:fse-fire-safety-objectives-v2.svg|thumb|upright=1.5|alt=Objective, exposed group, scenario, criterion and evidence form a traceable assessment chain.|Objectives must be translated into assessable criteria and evidence. Based on National Research Council of Canada et al. (2005), pp. 1.2-25–1.2-26.]]

Regulations sometimes fix the numbers themselves. In New Zealand, the objective of protecting other property is backed by limits on the radiation received from a fire. The radiation may not exceed 30 kW/m² at the boundary of the property, or 16 kW/m² at 1 m beyond it. These values belong to the New Zealand Building Code as applied in C/VM2 (second edition, 2025).<ref name="CVM2-43">Ministry of Business, Innovation and Employment (2025b), p. 43.</ref> In an absolute assessment, the values may instead be agreed in the fire engineering brief, and they should allow for uncertainty and safety factors.<ref name="IFEG-1-2-25" />

Two approaches are used to judge whether a design meets its objectives.<ref name="IFEG-1-2-21">National Research Council of Canada et al. (2005), p. 1.2-21.</ref> In a comparative approach, the trial design is compared with an otherwise identical building that follows the prescriptive rules.<ref name="IFEG-1-2-21" /> The same criteria are used for both, and the trial design should perform at least as well.<ref name="IFEG-1-2-25" /> In an absolute approach, the results are matched directly against the objectives using the agreed criteria.<ref name="IFEG-1-2-21" /> In Australia, the Fire Safety Verification Method compares the design with a reference building that follows the deemed-to-satisfy provisions. This can make the outcome less sensitive to the choice of inputs and methods.<ref name="ABCBDS-i">Australian Building Codes Board (2020a), p. i.</ref>

== How objectives guide the design ==

The Australian handbook defines a [[Fire safety strategy|fire safety strategy]] as a combination of physical and human measures, including maintenance and management, specified to achieve the nominated fire safety objectives.<ref name="ABCB-140">Australian Building Codes Board (2020b), p. 140.</ref> The design process normally starts by defining the relevant objectives, of the building code and any others, and then develops the strategy. The handbook describes fire safety engineering as a logical sequence from objectives and performance requirements to the strategy, fire scenarios, detailed analysis and the decision on compliance.<ref name="ABCB-20">Australian Building Codes Board (2020b), p. 20.</ref> The documented strategy should include a summary of the fire safety objectives.<ref name="ABCB-31">Australian Building Codes Board (2020b), p. 31.</ref>

Strategies link the objectives to concrete measures. Examples are ignition prevention, limitation of combustibles, compartmentation, detection and alarm, suppression and the protection of exposed people or things. A matrix of objectives against strategies shows how important each strategy is for each objective.<ref name="Watts-5-136" /> A single system can serve several objectives: smoke and heat venting is designed to help people escape, to let firefighters see the seat of the fire, and to reduce property damage.<ref name="Cooper-3-219">Cooper (2002b), p. 3-219.</ref> How well a system serves an objective depends on two factors. Efficacy is the degree to which it achieves a design objective when it works as specified, and reliability is the probability that it does work as specified.<ref name="ABCBDS-C4">Australian Building Codes Board (2020a), Data Sheet C4, p. 125.</ref>

The [[Fire safety concepts tree|fire safety concepts tree]], a diagram based on the judgements of an NFPA technical committee, starts from the fire safety objectives at its top. Below them, it splits into two branches: preventing fire ignition and managing the fire impact. One branch or the other must succeed for the objectives to be met. Ignition is prevented by controlling heat sources, their interaction with fuel, and the fuel itself. Fire impact is reduced either by managing the fire itself or by managing what is exposed to it. If ignition is not prevented, the tree helps to evaluate whether the systems of the building can manage the fire impact.<ref name="Meacham-5-158">Meacham (2002), p. 5-158.</ref>
[[File:fse-fire-safety-objectives-v3.svg|thumb|upright=1.5|alt=Fire-safety objectives branch into preventing ignition and managing fire impact.|Prevention and impact management provide complementary paths towards objectives. Based on Meacham (2002), p. 5-158.]]

In New Zealand, C/VM2 (second edition, 2025) tests a design against ten design scenarios that must each be satisfied separately. Each scenario is tied to one or more of the Building Code objectives.<ref name="CVM2-7" /> One scenario checks that the failure of a critical part of the fire safety system does not cause the design to miss those objectives. Each key system, such as smoke management or a fire door, is assumed to fail in turn, and the design is changed if the occupants could then no longer escape safely. Sprinklers and automatic fire alarms installed to a recognised standard are treated as reliable enough to be exempt.<ref name="CVM2-58" />

== Limits and common misconceptions ==

Fire safety objectives do not aim at absolute safety. For New Zealand and the United States, the International Fire Engineering Guidelines state that absolute safety and zero risk are not achievable. The accepted risk takes into account what the community expects and what safety costs the community.<ref name="IFEG-NZ-0-2-5" /><ref name="IFEG-US-0-2-8" /> The Australian handbook adds that removing all risk would bring the fire safety strategy into conflict with the function and use of the building.<ref name="ABCB-27" /> Objectives therefore aim at an acceptable or tolerable level of [[Fire risk|fire risk]], not at the absence of risk.<ref name="IFEG-CA-0-2-2" /><ref name="ABCB-27" />

Deriving that level from the regulations is difficult, because their actual outcomes differ widely between types of building. In the Netherlands, the chance of dying in a fire per hour of stay is much greater in a residential building than in an assembly building. Yet the requirements for fire detection are stricter for assembly buildings. For an engineering approach, the required performance or the accepted residual risk must therefore be agreed in advance, for example by comparison with a reference situation that follows the rules.<ref name="VR-1-2" /> The Netherlands has no risk-based limit values, a drawback for quantitative analysis there.<ref name="VR-1-4" />

Objectives also carry values and uncertainty. The SFPE Handbook (2002) notes that no significant work has been done to identify what fire safety is trying to achieve, so lists of objectives are very subjective.<ref name="Watts-5-136" /> Few studies show how society values fire safety risks at the level needed for performance-based trade-offs.<ref name="Notarianni-5-46" /> Uncertainty arises in the science, in human behaviour, in perceptions of risk and values, and in decision making itself. Some people are risk tolerant, while others are risk averse.<ref name="Meacham-5-160">Meacham (2002), p. 5-160.</ref>

Meeting one objective does not mean meeting the others. Two designs may be equivalent for life safety but not for property protection, business interruption or structural collapse. The conditions behind the objectives also change over the life of a building, because its use, its occupants and even the fire service may change.<ref name="Notarianni-5-46" /> The fire safety of a building depends on its fire safety system continuing to work and on management limits, such as fuel loads and free escape routes, being respected. When a building is altered or its use changes, the existing fire engineering evaluation may have to be re-examined to see whether it still applies.<ref name="IFEG-NZ-0-3-8">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-8.</ref>

== See also ==

* [[Qualitative design review]]
* [[Performance-based design]]
* [[Prescriptive design]]
* [[Equivalency]]
* [[Fire scenario]]
* [[Fire safety management]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr. (2002). Fire risk indexing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-125–5-142). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Safety Design & Regulation]]

SFPE

2026-11-02T18:39:10Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''SFPE''', the Society of Fire Protection Engineers, is an organisation in the United States that represents fire protection engineers.<ref name="NIST-201">National Institute of Standards and Technology (2005), p. 201.</ref> It is based in Bethesda, Maryland.<ref name="DiNenno-iii">DiNenno et al. (2002), pp. iii–iv.</ref> The International Fire Engineering Guidelines (IFEG, 2005) list SFPE among the organisations that publish and provide knowledge for fire engineering.<ref name="IFEG-US-05">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.5-6–0.5-10.</ref> Its publications include the ''SFPE Handbook of Fire Protection Engineering'', engineering guides on subjects such as performance-based design, and engineering standards such as one on calculating fire exposures to structures.<ref name="DiNenno-iii" /><ref name="Notarianni-42">Notarianni (2002), p. 5-42.</ref><ref name="ABCB-B1">Australian Building Codes Board (2020a), Data Sheet B1, p. 12.</ref>

SFPE has also developed a Canon of Ethics for Fire Protection Engineers, to which the IFEG refer for professional issues outside their own scope.<ref name="IFEG-US-01">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.1-1–0.1-4.</ref> Its publications are used well beyond the United States. In New Zealand, Verification Method C/VM2 (second edition, 2025) refers to the SFPE Handbook for evacuation calculations.<ref name="MBIE-26">Ministry of Business, Innovation and Employment (2025b), pp. 26, 33.</ref> In Australia, the 2020 handbook for the Fire Safety Verification Method cites SFPE engineering standards.<ref name="ABCB-H">Australian Building Codes Board (2020b), pp. 109, 113.</ref> SFPE is a separate body from the National Fire Protection Association, which publishes the SFPE Handbook and develops codes and standards of its own.<ref name="DiNenno-iii" /><ref name="Iqbal-E1">Iqbal and Salley (2004), p. E-1.</ref>

== Fire protection engineering and the society ==

SFPE describes fire protection engineering as the application of science and engineering principles to protect people and their environment from destructive fire.<ref name="IFEG-US-03">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-1–0.3-2.</ref> In this description the field includes the analysis of fire hazards. It also covers reducing fire damage through the design, construction, arrangement and use of buildings, materials, structures, industrial processes and transport systems.<ref name="IFEG-US-03" /> A third part is the design, installation and maintenance of fire detection, suppression and communication systems, and a fourth is investigation and analysis after a fire.<ref name="IFEG-US-03" /> In the SFPE wording, a fire protection engineer knows through education, training and experience how fires start and spread, and how they can be detected, controlled or extinguished.<ref name="IFEG-US-03" /> Such an engineer can also anticipate how materials, structures and processes behave in fire.<ref name="IFEG-US-03" />

The term "fire protection engineer" is common in the United States, but the IFEG mainly use "fire engineer", which they consider a better international description of the engineer who applies their design methods.<ref name="IFEG-US-01" /> The guidelines take their definition of [[Fire safety engineering|fire engineering]] from the International Organization for Standardization (ISO).<ref name="IFEG-US-03" /> In it, fire engineering is the application of engineering principles, rules and expert judgement based on a scientific appreciation of fire, its effects and the behaviour of people.<ref name="IFEG-US-03" /> Its aims include saving life, protecting property, preserving the environment and heritage, quantifying the hazards and risk of fire, and evaluating the measures needed to limit its consequences to prescribed levels.<ref name="IFEG-US-03" />

NIST, the US National Institute of Standards and Technology, counts SFPE among the organisations that represent engineers, such as the National Society of Professional Engineers.<ref name="NIST-201" /> It distinguishes these groups from the organisations that develop codes and standards, and notes that they also provide training, especially where training affects how code provisions are applied in practice.<ref name="NIST-201" /> SFPE also carries out periodic surveys of the industry to understand what roles fire protection engineers play.<ref name="IFEG-US-01" /> The IFEG list two SFPE periodicals, the ''Journal of Fire Protection Engineering'' and the ''SFPE Journal'', among the journals useful to fire engineering professionals.<ref name="IFEG-US-05" /> In New Zealand, the IFEG note that fire engineers may be approved for full membership of bodies such as SFPE once they have shown appropriate qualifications and experience. Membership of an institution does not, however, necessarily prove the competence of an individual.<ref name="IFEG-NZ-04">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.4-2.</ref>

== The SFPE Handbook ==

The third edition (2002) of the ''SFPE Handbook of Fire Protection Engineering'' is copyrighted by SFPE and published by the [[NFPA|National Fire Protection Association]] (NFPA) in Quincy, Massachusetts.<ref name="DiNenno-iii" /> Philip J. DiNenno was editor-in-chief, with six section editors from consultancies, a university, NIST, NFPA and The Fire Safety Institute.<ref name="DiNenno-iii" /> Its 72 chapters, each written by named authors, are grouped into five sections: Fundamentals, Fire Dynamics, Hazard Calculations, Design Calculations and Fire Risk Analysis.<ref name="DiNenno-v">DiNenno et al. (2002), pp. v–viii.</ref> Appendices then give data such as conversion factors, thermophysical properties of materials and fuel properties.<ref name="DiNenno-v" />
[[File:fse-sfpe-v1.svg|thumb|upright=1.5|alt=Fundamentals and hazard methods support design and risk analysis in the handbook.|The handbook combines specialist technical subjects. Based on DiNenno et al. (2002), pp. iii–vii.]]

In the preface, DiNenno describes the handbook as a contribution towards documenting and integrating the theoretical and applied bases of fire safety engineering.<ref name="DiNenno-ix">DiNenno et al. (2002), pp. ix–x.</ref> According to the preface, the rapid assimilation of performance-based design had underscored its importance.<ref name="DiNenno-ix" /> The third edition added chapters on heat fluxes from fires to surfaces, water mist systems and computer field modelling, and more material on risk assessment.<ref name="DiNenno-ix" /> Part of the new material on radiation heat transfer came from an SFPE technical committee working towards consensus on engineering methods.<ref name="DiNenno-ix" /> The editors expected future editions to include the work of several engineering consensus groups aiming at a consensus-based standard of care in fire safety engineering.<ref name="DiNenno-ix" />

Other documents draw on the handbook as well. NUREG-1805, a 2004 report for the US Nuclear Regulatory Commission, derived the technical basis of its Fire Dynamics Tools primarily from the SFPE Handbook and the NFPA Fire Protection Handbook.<ref name="Iqbal-xxxvii">Iqbal and Salley (2004), p. xxxvii.</ref> The IFEG name the SFPE Handbook among the textbooks that give methods for smoke production, smoke layer height, upper layer temperature and smoke movement.<ref name="IFEG-2-5">National Research Council of Canada et al. (2005), p. 2.5-2.</ref> In New Zealand, C/VM2 (2025) refers readers to Section 3, Chapter 13 of the fourth edition (2008) for more information on calculating the required safe egress time and on egress calculation procedures.<ref name="MBIE-26" /><ref name="MBIE-61">Ministry of Business, Innovation and Employment (2025b), p. 61.</ref>

The textbook ''Introduction to Fire Safety Engineering'' also takes values from the handbook. Its walking speeds for different groups, for example, range from 0.58 m/s for people with a walking frame to 1.25 m/s for healthy, unimpeded people.<ref name="VR-7.4">Van Rossum (2027), §7.4.</ref> From the same source it takes the smoke potential, which expresses how much light the smoke from one kilogram of burnt material blocks.<ref name="VR-6.4">Van Rossum (2027), §6.4.</ref> In fires this is usually 3,300 m²/kg, a generic average for burning building and furnishing materials.<ref name="VR-6.4" />

== Engineering guides and standards ==

Besides the handbook, SFPE publishes engineering guides that evaluate calculation methods for particular problems. In the handbook chapter on large hydrocarbon fires, Beyler explains that the methods for radiation from pool fires were evaluated and included in an SFPE engineering guide.<ref name="Beyler-272">Beyler (2002a), p. 3-272.</ref> In that guide the methods are described in full, their assumptions are identified and their limits of applicability are assessed.<ref name="Beyler-272" /> The guide also lists available input data and compares the accuracy of the methods with experimental data.<ref name="Beyler-272" /> These [[Hand calculations|hand calculations]] range from very crude initial hazard assessments to detailed methods that need more engineering effort.<ref name="Beyler-272" /> Where a simple method shows that a separation distance is far larger than needed for safety, a more rigorous analysis may not be necessary.<ref name="Beyler-272" />

A related SFPE guide of 2000 treats skin burns from thermal radiation in more detail than the handbook.<ref name="Beyler-308">Beyler (2002a), pp. 3-308, 3-313.</ref> In New Zealand, C/VM2 (2025) points to that guide where occupants escape past more than one window, because the time-dependent build-up of radiation must then be calculated.<ref name="MBIE-34">Ministry of Business, Innovation and Employment (2025b), pp. 34–35.</ref> For computer fire models, SFPE published Guidelines for Substantiating a Fire Model for a Given Application (2011). A 2016 validation study for the NRC names them as a useful reference next to the ASTM standard that the study follows.<ref name="Stroup">Stroup et al. (2016), p. 1-3.</ref>

Such guidance does not make a calculation tool self-validating. NUREG-1805 asks first-time users to read the whole report before an analysis and to apply its spreadsheet tools only within the limits of their validity.<ref name="Iqbal-xxxix">Iqbal and Salley (2004), p. xxxix.</ref> The IFEG add that even an expensive and highly sophisticated computer model does not guarantee accurate results, so all model output must be reviewed and verified.<ref name="IFEG-2-8">National Research Council of Canada et al. (2005), p. 2.8-4.</ref> They also describe a hydraulic method for evacuation from the SFPE Handbook, which assumes among other things that all occupants start to leave at the same time.<ref name="IFEG-2-8" />
[[File:fse-sfpe-v2.svg|thumb|upright=1.5|alt=Scenario inputs pass through a bounded hand calculation and independent plausibility review.|Hand calculations require valid inputs and critical review. Based on Iqbal and Salley (2004), p. xxxix and National Research Council of Canada et al. (2005), p. 2.8-4.]]

SFPE also issues engineering standards. The Australian data sheets for the Fire Safety Verification Method (2020) cite SFPE S.01 (2011), a standard on calculating fire exposures to structures, as a standardised approach to predicting flashover.<ref name="ABCB-B1" /> For fire models, it gives as criteria for flashover an upper layer temperature above 600 °C or a heat flux to the floor above 20 kW/m².<ref name="ABCB-B1" /> The accompanying handbook lists S.01 among the methods for fully developed fires.<ref name="ABCB-H" /> It names SFPE S.02 (2015) as a source of examples for checking heat transfer models, a process known as validation and verification.<ref name="ABCB-H" /> In the United States, NIST recommended in 2005 that standards committees draw on the ASCE/SFPE 29 standard for fire resistance design when they address progressive collapse under fire conditions.<ref name="NIST-206">National Institute of Standards and Technology (2005), pp. 206, 212.</ref>

== Performance-based design ==

For [[Performance-based design|performance-based design]], SFPE published its Engineering Guide to Performance-Based Fire Protection Analysis and Design of Buildings in 2000.<ref name="IFEG-US-01" /> The guide is meant for both design engineers and approving authorities.<ref name="Notarianni-42" /> Its stated intent is to help them determine and document that agreed levels of fire safety are achieved for a particular project.<ref name="Notarianni-42" /> Its steps are to define the project scope, identify goals, define objectives, develop performance criteria, develop fire scenarios, develop and evaluate candidate designs, and select and document the final design.<ref name="Notarianni-42" /> The documentation has four parts: a fire protection engineering design brief, a performance design report, detailed specifications and drawings, and a building operations and maintenance manual.<ref name="Notarianni-60">Notarianni (2002), p. 5-60.</ref>

The guide also gives a method for quantifying the fire risk from several fire scenarios. The total risk is the sum, over all fire scenarios considered, of the loss in each scenario multiplied by how often that scenario occurs.<ref name="Meacham">Meacham (2002), p. 5-161.</ref> Watts and Hall (2002) note that SFPE addresses the basics of fire risk analysis in its publications on performance-based design, and that SFPE task groups were adding further detail.<ref name="WattsHall">Watts and Hall (2002), pp. 5-6–5-7.</ref>

Other guidance builds on this work. The IFEG drew on the 2000 SFPE guide and on a Code Officials Guide to Performance-Based Design Review that SFPE produced with the International Code Council in 2004.<ref name="IFEG-US-01" /> For the United States, the IFEG call both documents good resources for deriving goals and objectives where no performance code has been adopted.<ref name="IFEG-US-02">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-9.</ref> They also mention SFPE work towards a consistent method for determining design fires.<ref name="IFEG-US-02" /> In addition, the IFEG recommend both guides as a benchmark for third-party reviewers of fire engineering reports.<ref name="IFEG-US-03-9">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-8–0.3-9.</ref> In New Zealand, C/VM2 (2025) lists SFPE, with the IFEG and British Standards, among the publishers of internationally recognised documents on the fire engineering brief process.<ref name="MBIE-7">Ministry of Business, Innovation and Employment (2025b), p. 7.</ref>

== Uncertainty and limits ==

SFPE guidance does not remove uncertainty from performance-based design. Notarianni (2002) describes a review of the design process in the SFPE guide and of several case studies of real designs.<ref name="Notarianni-42" /> The review found seven barriers to documenting that agreed levels of fire safety had been reached.<ref name="Notarianni-42" /> The first two are performance criteria that are not established or agreed, and an unspecified process for choosing design fires.<ref name="Notarianni-43">Notarianni (2002), pp. 5-43–5-44.</ref> Others are assumptions about human behaviour, poorly documented limits of fire models and model outputs given as single values.<ref name="Notarianni-43" /> The last two are engineers working beyond their expertise and the lack of a standard way to include the reliability of fire protection systems.<ref name="Notarianni-43" />

Each barrier can lead to switchover, in which reasonable changes in inputs, scenarios or parameters change the decision on whether a design is acceptable.<ref name="Notarianni-42" /> In one example, two engineers who had both followed the current design guidelines for real buildings chose very different performance criteria.<ref name="Notarianni-43" /> Because model predictions are compared with such criteria, the same design can pass under one set and fail under another.<ref name="Notarianni-43" />
[[File:fse-sfpe-v3.svg|thumb|upright=1.5|alt=Changed criteria, scenarios, behaviour and model assumptions lead to different acceptability outcomes.|Uncertainty can change a design from acceptable to unacceptable. Based on Notarianni (2002), pp. 5-43–5-44.]]

Human behaviour is a particular source of uncertainty. Proulx (2002) warns that research has shown some traditional assumptions about behaviour in fires to be wrong.<ref name="Proulx">Proulx (2002), pp. 3-342–3-343.</ref> She also cites the observation that the hydraulic model of evacuation assumes occupants who are alert, able-bodied and ambulatory, and deals only with movement, not with the time people take to start.<ref name="Proulx" /> Notarianni adds that one internationally used egress model assumes that all occupants are readily mobile and leave as soon as they hear an alarm.<ref name="Notarianni-43" /> Experience shows that this is often not the case.<ref name="Notarianni-43" />

The handbook also has practical limits. Some of its equations, tables and charts keep US customary units because their data were originally developed in those units.<ref name="DiNenno-ix" /> Its notice states that neither the publisher nor the authors guarantee the accuracy or completeness of the contents, and that they supply information and opinion rather than engineering services.<ref name="DiNenno-iii" /> Where such services are needed, the notice advises seeking the help of an appropriate professional.<ref name="DiNenno-iii" />

== Ethics and professional practice ==

One of SFPE's contributions to [[Ethics in fire safety engineering|ethics in fire safety engineering]] is its Canon of Ethics for Fire Protection Engineers, which the IFEG quote in part.<ref name="IFEG-US-04">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.4-2.</ref> Its preamble calls fire protection engineering an important learned profession whose work has a direct and vital impact on the quality of life of all people.<ref name="IFEG-US-04" /> The services of fire protection engineers therefore require honesty, impartiality, fairness and equity, and must be dedicated to protecting and enhancing public safety, health and welfare.<ref name="IFEG-US-04" /> Engineers are expected to maintain and constantly improve their competence and to act with balanced regard for the interests of the public, clients, employers, colleagues and the profession.<ref name="IFEG-US-04" />

Three fundamental principles follow from the preamble. Fire protection engineers use their knowledge and skill for the enhancement of human welfare.<ref name="IFEG-US-04" /> They are honest and impartial and serve the public, their employers and their clients with fidelity.<ref name="IFEG-US-04" /> They also strive to increase the competence and prestige of their profession.<ref name="IFEG-US-04" /> The IFEG state that the canon deals with professional issues outside their own scope and should be consulted as appropriate.<ref name="IFEG-US-01" />

SFPE also has a role in education. After its World Trade Center investigation, NIST named SFPE in 2005 among the organisations affected by its recommendation to develop continuing education for fire protection engineers, structural engineers and architects.<ref name="NIST-222">National Institute of Standards and Technology (2005), pp. 222–223.</ref> It also named SFPE for training material on computational fire dynamics and thermostructural analysis tools.<ref name="NIST-222" /> For NIST's report on the active fire protection systems of the World Trade Center, an SFPE engineering programmes manager supplied introductory and summary material.<ref name="Evans">Evans et al. (2005), p. xxvii.</ref> Its purpose was to give all readers a common basis for understanding the results.<ref name="Evans" />

== Relationship with NFPA and with regulation ==

SFPE and NFPA are separate organisations with different roles. NFPA develops and publishes consensus codes and standards, whereas NIST groups SFPE with the organisations that represent engineers.<ref name="Iqbal-E1" /><ref name="NIST-201" /> The IFEG list the two as distinct bodies that publish fire engineering knowledge.<ref name="IFEG-US-05" /> They work together on publications: SFPE holds the copyright of the SFPE Handbook and NFPA publishes it.<ref name="DiNenno-iii" /> NIST also named both in 2005 for work on standard methods for multi-floor design fire scenarios.<ref name="NIST-206" />

SFPE guides and standards are not regulations in themselves. A NIST report on the World Trade Center explains that trade associations and professional societies develop practices that may guide how buildings are designed and built.<ref name="Lew">Lew et al. (2005), p. 142.</ref> Such practices are not strictly enforceable unless a code refers to them, but they represent a consensus of what is reasonable or prudent.<ref name="Lew" /> Where a regulatory document does refer to SFPE material, it does so selectively. C/VM2 (2025), for example, cites the SFPE Handbook and an SFPE guide only in particular comments and clauses.<ref name="MBIE-61" /> Showing compliance with the New Zealand Building Code through C/VM2 still requires each of its ten design scenarios to be satisfied.<ref name="MBIE-7" />

C/VM2 is meant for professional fire engineers who are proficient in fire engineering modelling methods.<ref name="MBIE-7" /> They are expected to apply appropriate judgement to model inputs and results.<ref name="MBIE-7" /> The IFEG likewise allow engineering judgement where valid methods or verified data are not available, but require all quantification based on it to be justified in detail.<ref name="IFEG-1-8">National Research Council of Canada et al. (2005), p. 1.8-10.</ref> For the United States, they give the fire engineer the task of evaluating a performance design and the authority having jurisdiction the task of assessing and approving it.<ref name="IFEG-US-0211">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-11.</ref>

== See also ==

* [[Acceptance criteria]]
* [[Fire scenario]]
* [[Fire safety objectives]]
* [[Qualitative design review]]
* [[Building regulations]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Beyler, C. L. (2002a). Fire hazard calculations for large, open hydrocarbon fires. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-268–3-314). National Fire Protection Association; Society of Fire Protection Engineers.
* DiNenno, P. J., Drysdale, D., Beyler, C. L., Walton, W. D., Custer, R. L. P., Hall, J. R., Jr., & Watts, J. M., Jr. (Eds.). (2002). ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Proulx, G. (2002). Movement of people: The evacuation timing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-342–3-366). National Fire Protection Association; Society of Fire Protection Engineers.
* Stroup, D., Lindeman, A., McGrattan, K., Peacock, R., Overholt, K., Joglar, F., LeStrange, S., & Montanez, S. (2016). ''Verification and validation of selected fire models for nuclear power plant applications: Supplement 1'' (NUREG-1824, Supplement 1; EPRI 3002002182). U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research; Electric Power Research Institute.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Safety Design & Regulation]]

NFPA

2026-11-02T18:38:50Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''NFPA''', the National Fire Protection Association, is an organisation that develops, publishes and distributes consensus codes and standards intended to minimise the possibility and effects of fire and other risks.<ref name="Iqbal-E1">Iqbal and Salley (2004), p. E-1.</ref> It is based in Quincy, Massachusetts, in the United States.<ref name="DiNenno-iii">DiNenno et al. (2002), pp. iii–iv.</ref> In 2004 more than 300 of these codes and standards were in use around the world, together forming the series known as the National Fire Codes.<ref name="Iqbal-E1" /> They carry great weight because governments at all levels, from local to international, use them as a basis for legislation and regulation.<ref name="Iqbal-E1" /> Insurers also use them for risk evaluation, and designers cite them in designs and specifications.<ref name="Iqbal-E1" />

In the United States, the building and fire safety regulations of states and local jurisdictions are based on model codes developed by two private-sector organisations, the International Code Council and NFPA.<ref name="NIST-201">National Institute of Standards and Technology (2005), p. 201.</ref> An NFPA document is not law in itself, however: it becomes binding only when a jurisdiction adopts it, often with local changes and not always in its latest edition.<ref name="Lew-142">Lew et al. (2005), p. 142.</ref><ref name="Keough-2">Keough and Grill (2005), p. 2.</ref> NFPA also runs an annual survey of fire departments that underpins national fire loss estimates in the United States.<ref name="Hall-Ahrens-67">Hall and Ahrens (2002), pp. 5-67–5-68.</ref> In addition, it publishes engineering reference works, such as the third edition of the ''SFPE Handbook of Fire Protection Engineering''.<ref name="DiNenno-iii" />

== Codes, standards and guides ==

NFPA documents are identified by a number and an edition year, and they include codes, standards, recommended practices and guides.<ref name="Iqbal-E">Iqbal and Salley (2004), pp. E-1–E-13.</ref> NUREG-1805, a 2004 report for the US Nuclear Regulatory Commission (NRC), lists them from NFPA 1, the Uniform Fire Code, to NFPA 5000, the Building Construction and Safety Code.<ref name="Iqbal-E" /> Between them are installation documents such as NFPA 13 for sprinkler systems, the National Electrical Code (NFPA 70) and the National Fire Alarm Code (NFPA 72).<ref name="Iqbal-E" /> There are also fire test methods, such as NFPA 251 for the fire endurance of building construction, and standards on the professional qualifications of firefighters and fire investigators.<ref name="Iqbal-E" /> Guides used in fire safety engineering include NFPA 550, the Guide to the Fire Safety Concepts Tree, and NFPA 551, the Guide for the Evaluation of Fire Risk Assessments.<ref name="Iqbal-E" />

NFPA documents are developed and maintained by technical committees, and the members of these committees include practitioners from outside NFPA.<ref name="WattsHall-7">Watts and Hall (2002), p. 5-7.</ref> Russell Fleming, vice-president of engineering at the National Fire Sprinkler Association, had served on more than a dozen of them, including the Committee on Automatic Sprinklers.<ref name="Fleming-72">Fleming (2002), p. 4-72.</ref> A committee can also change the status of a document. After discussions in the 1970s on the phased evacuation of tall buildings, an NFPA committee developed a guide for emergency voice communication systems, NFPA 72F, which was later made a standard.<ref name="Lew-162">Lew et al. (2005), p. 162.</ref> In 2002 the SFPE Handbook reported a new NFPA Technical Committee on Fire Risk Analysis.<ref name="WattsHall-7" /> Its purpose was to give the other committees guidance on methods and concepts of fire risk analysis.<ref name="WattsHall-7" />

Two NFPA codes cover buildings rather than individual systems. In the early 1900s NFPA began developing a "life safety code" for the safety of building occupants.<ref name="Lew-37">Lew et al. (2005), p. 37.</ref> This code, NFPA 101, is not a building code, but it is frequently used as a supplement to building codes.<ref name="Lew-37" /><ref name="Lew-141">Lew et al. (2005), p. 141.</ref> NIST, the US National Institute of Standards and Technology, describes NFPA 101 as widely adopted for its requirements on life safety in fires.<ref name="Lew-141" /> In 2002 NFPA also published a model building code of its own, the Building Construction and Safety Code (NFPA 5000).<ref name="Lew-37" />

== From document to legal requirement ==

In the United States, building regulations are a task of state and local governments. These can either write their own regulations or adopt a model building code developed by a not-for-profit membership organisation.<ref name="IFEG-US-02">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.2-2–0.2-5.</ref> Using a model code is the main choice, and the codes are adopted with varying levels of amendment.<ref name="IFEG-US-02" /> The model codes in turn adopt by reference voluntary consensus standards from private standards development organisations, among them NFPA and ASTM International.<ref name="NIST-201" /> In June 2005 NIST reported that NFPA's National Electrical Code was used in virtually all US jurisdictions.<ref name="NIST-201" />

These model codes and referenced standards do not become law until a jurisdiction that is empowered to enforce regulations adopts them, either by legislation or administratively.<ref name="Lew-142" /> The jurisdiction may modify specific provisions to suit local conditions and practice, and once adopted, the modified codes and standards together are referred to as [[Building regulations|building regulations]].<ref name="Lew-142" /> When standards are referenced in the building regulations in this way, they are legally binding.<ref name="IFEG-US-02" /> A few federal rules, for example for hospitals, also require compliance with documents such as NFPA 101 in addition to the requirements of the state.<ref name="IFEG-US-02" />
[[File:fse-nfpa-v1.svg|thumb|upright=1.5|alt=NFPA documents pass through jurisdiction-specific adoption before becoming legal requirements.|Legal effect depends on adoption, scope and edition. Based on Keough and Grill (2005), pp. 1–2 and Iqbal and Salley (2004), p. E-1.]]

New York City shows how far an adopted text can differ from the published one. Its building code adopted sections, but not the full content, of the National Fire Alarm Code and the National Electrical Code as a city Reference Standard.<ref name="Keough-2" /> The editions it referenced were not the latest ones.<ref name="Keough-2" /> The city's general fire alarm requirements in Reference Standard RS 17-5 were based on NFPA 72 but highly modified, with many sections deleted and many others changed.<ref name="Lew-150">Lew et al. (2005), p. 150.</ref> Most other building codes, by contrast, reference the national consensus standards as published.<ref name="Lew-150" />

Building regulation is not the only route by which NFPA documents take effect. Many NFPA codes are referenced in the regulations of US federal agencies such as the NRC, the General Services Administration and the Occupational Safety and Health Administration.<ref name="Iqbal-E1" /> In New Zealand, the 2013 commentary on Verification Method C/VM2 explains that the ten design scenarios of that method are partly based on the scenarios in NFPA 5000. They were modified and expanded to cover, for example, fire spread to neighbouring property and firefighting facilities.<ref name="MBIE-121">Ministry of Business, Innovation and Employment (2013), p. 121.</ref> The Australian handbook for the Fire Safety Verification Method (2020) likewise names NFPA 5000, together with C/VM2, as an example of prescribing the design scenarios that an analysis must consider.<ref name="ABCB-H-8">Australian Building Codes Board (2020b), p. 8.</ref>

== Editions and the code of record ==

NFPA codes and standards are constantly revised and updated on cycles of three to five years.<ref name="Iqbal-E1" /> NUREG-1805 calls the code or standard in effect at the time of design or implementation the code of record for that application.<ref name="Iqbal-E1" /> Keough and Grill (2005) explain the consequence. A code or standard in effect when a system is designed applies to that system during its existence, even if the authority adopts newer editions before the project is completed.<ref name="Keough-2" /> Because of the time lag between the development of a code and its adoption, the most recent edition is usually not applicable to a project unless it contains retroactive provisions.<ref name="Keough-2" />
[[File:fse-nfpa-v2.svg|thumb|upright=1.5|alt=New editions move through adoption into project-specific code-of-record decisions.|The newest edition is not automatically the applicable edition. Based on Keough and Grill (2005), pp. 1–2 and Iqbal and Salley (2004), p. E-1.]]

Retroactive provisions are the exception rather than the rule. Normal practice is not to apply building code changes to existing buildings unless they undergo major renovation or a change in primary use.<ref name="Lew-141" /> Even so, two New York City local laws of 1973 and 1984 contained retroactive provisions.<ref name="Lew-141" /> The Life Safety Code is a notable case, because NIST notes that NFPA 101 applies retroactively to all buildings, whether or not any work is being done on them.<ref name="NIST-221">National Institute of Standards and Technology (2005), p. 221.</ref>

Edition control matters outside the United States as well. The first edition of the New Zealand C/VM2 required its referenced documents to be used in the editions it listed, among them NFPA 285 of 1998, a fire test for exterior walls.<ref name="MBIE-3-4">Ministry of Business, Innovation and Employment (2013), pp. 3–4.</ref> The second edition of C/VM2 (2025) removed its references to building product standards, including NFPA 285, and points instead to separate Building Product Specifications.<ref name="MBIE25-3">Ministry of Business, Innovation and Employment (2025b), p. 3.</ref> The Australian data sheets of 2020 cite NFPA 72 in its 2019 edition, whereas the NUREG-1805 list of 2004 gives the 2002 edition.<ref name="ABCB-C3-109">Australian Building Codes Board (2020a), Data Sheet C3, pp. 109–111.</ref><ref name="Iqbal-E" />

A specialised example of edition and change control comes from US nuclear power plants. NFPA completed NFPA 805, a performance-based standard for fire protection at light water reactor electric generating plants, in 2001.<ref name="Hyslop">Hyslop et al. (2010), p. 1-1.</ref> From 16 July 2004 the NRC allowed existing reactor licensees to adopt it voluntarily as an alternative to the existing deterministic fire protection requirements.<ref name="Hyslop" /> Under NFPA 805 and the rule that adopts it, any change to a previously approved element of the fire protection programme requires a change evaluation.<ref name="Hyslop" /> Such elements include system design, maintenance, procedures and impairments.<ref name="Hyslop" />

== Sprinkler and fire alarm standards ==

For [[Sprinkler system|sprinkler systems]], the central document is NFPA 13, a design and installation standard for automatic sprinkler systems that is referenced by most building codes in the United States and Canada.<ref name="Fleming-73">Fleming (2002), p. 4-73.</ref> For the water supply, NFPA 13 refers to other NFPA standards, such as NFPA 20 for fire pumps, NFPA 22 for water tanks and NFPA 24 for private fire service mains.<ref name="Fleming-73" /> From its 1999 edition NFPA 13 also absorbed the special standards for warehouse storage, which had contained their own sprinkler design criteria.<ref name="Fleming-73" /> A further standard, NFPA 25, covers the inspection, testing and maintenance of water-based fire protection systems.<ref name="Iqbal-E" />

Fleming (2002) stresses that the fire suppression side of sprinkler design is empirical. Some criteria rest on full-scale tests, such as those for large drop and early suppression fast response sprinklers.<ref name="Fleming-73" /> Most NFPA 13 protection criteria, however, are the result of evolution and experienced judgement.<ref name="Fleming-73" /> In the 1970s the capabilities of pipe schedule systems, which had shown a hundred years of satisfactory performance, were codified into area/density curves. This opened the way for hydraulic calculations of the water flow through the piping.<ref name="Fleming-73" /> Classifying the occupancy hazard remains the most critical step of the design and requires experienced judgement and familiarity with the relevant NFPA standards.<ref name="Fleming-73" />

NFPA published the first fire alarm signalling standard in 1899, the first of many editions that led to the National Fire Alarm Code (NFPA 72).<ref name="Keough-2" /> Keough and Grill (2005) call NFPA 72 the baseline standard used throughout the United States for fire alarms.<ref name="Keough-2" /> It gives performance requirements for the equipment and devices of a [[Fire alarm system|fire alarm system]].<ref name="Keough-2" /> It does not say where a system or its devices are required, because that follows from the building code of the jurisdiction.<ref name="Keough-2" /> The National Electrical Code (NFPA 70) covers how the supporting cables and hardware are installed, not which devices are needed.<ref name="Keough-2" />

Parts of NFPA 72 also serve as engineering data. The t-squared growth rate, the most popular way of estimating how a design fire grows, was originally developed in the 1970s to predict the activation of fire detectors.<ref name="MBIE-53">Ministry of Business, Innovation and Employment (2013), p. 53.</ref> It became popular when it was included in the appendix of NFPA 72, which defines slow, medium and fast fires by the time they take to reach 1055 kW.<ref name="MBIE-53" /> The Australian data sheets for the Fire Safety Verification Method name Appendix B of NFPA 72 as an example of guidance on calculating the activation times of smoke and heat detectors.<ref name="ABCB-C3-100">Australian Building Codes Board (2020a), Data Sheet C3, p. 100.</ref>

== Fire data and research ==

NFPA also contributes to the [[Fire statistics|fire statistics]] of the United States. National estimates of fire experience combine detailed data from the National Fire Incident Reporting System (NFIRS) of the US Fire Administration with NFPA's annual survey of fire departments.<ref name="Hall-Ahrens-67" /> The survey is used to scale the NFIRS data up to national totals.<ref name="Hall-Ahrens-67" /> NFIRS captures roughly a million fire incidents a year, but this is only an estimated half of the fires reported to US fire departments.<ref name="Hall-Ahrens-67" /> The NFPA survey is a stratified random sample of roughly one-tenth of all US fire departments, including most of those that protect a population of at least 100,000.<ref name="Hall-Ahrens-67" /> Its sampling uncertainty is about 10 per cent for deaths and much less for other measures of fire loss.<ref name="Hall-Ahrens-67" />

Two NFPA staff members, John R. Hall Jr. and Martha J. Ahrens, wrote the chapter on data for engineering analysis in the SFPE Handbook.<ref name="Hall-Ahrens-65">Hall and Ahrens (2002), p. 5-65.</ref> At the time, Hall was NFPA's assistant vice-president for fire analysis and research, and Ahrens was a fire analysis specialist.<ref name="Hall-Ahrens-65" /> They group the data needed for fire hazard and fire risk analysis into incident and field observation data, usage or exposure data, and laboratory test results.<ref name="Hall-Ahrens-65" /> Exposure data supply the denominators of rates, such as the number of portable heaters in use or the floor area of offices. With these, a count of fires becomes a frequency, such as fires per year per heater in use.<ref name="Hall-Ahrens-65" />
[[File:fse-nfpa-v3.svg|thumb|upright=1.5|alt=Incident records, exposure data, field observations and tests support analysis.|Main types of data for fire analysis. The arrows show examples of use; hazard and risk analyses typically need the same generic types of data. Based on Hall and Ahrens (2002), pp. 5-65–5-67.]]

Analyses of NFPA data are also used outside the United States. The Australian data sheets for the Fire Safety Verification Method (2020) take values for wet pipe sprinkler systems from an NFPA analysis of US fires in 2007–2011.<ref name="ABCB-C2">Australian Building Codes Board (2020a), Data Sheet C2, p. 76.</ref> In residential properties, the sprinklers operated in 95 per cent of the fires large enough to activate them.<ref name="ABCB-C2" /> They were effective in 97 per cent of those fires, so they operated effectively in 92 per cent.<ref name="ABCB-C2" /> The same data sheets draw on NFPA's periodic report on smoke alarms in US home fires, whose 2015 edition covers 2009–2013.<ref name="ABCB-C3-109" /> In that period, battery-powered smoke alarms operated in 80 per cent of the home fires large enough to activate them, and hard-wired alarms with battery backup in 95 per cent.<ref name="ABCB-C3-109" />

NFPA has also taken part in research on human behaviour in fire. In the days after the attacks of 11 September 2001, NFPA and the National Research Council Canada began to collect published first-person accounts of World Trade Center survivors.<ref name="Fahy-1">Fahy and Proulx (2005), p. 1.</ref> The material was coded and analysed to understand the evacuation experiences of survivors on different floors of the two towers.<ref name="Fahy-1" /> NIST contracted the two organisations to index a collection of more than 700 previously published interviews with survivors for its own investigation.<ref name="NIST-157">National Institute of Standards and Technology (2005), p. 157.</ref> The SFPE Handbook adds that fire risk analysis methods have been a recurring emphasis of projects organised by NFPA's Fire Protection Research Foundation.<ref name="WattsHall-7" />

== Engineering publications and performance-based design ==

NFPA also publishes reference works for fire safety engineering, such as the third edition of the SFPE Handbook (2002), whose copyright belongs to the [[SFPE|Society of Fire Protection Engineers]].<ref name="DiNenno-iii" /> One of the two editors of the handbook's section on fire risk analysis came from NFPA.<ref name="DiNenno-iii" /> NUREG-1805 derived the technical basis of its fire hazard calculation tools primarily from this handbook and from the NFPA Fire Protection Handbook.<ref name="Iqbal-xxxvii">Iqbal and Salley (2004), p. xxxvii.</ref> The International Fire Engineering Guidelines (IFEG, 2005) list two NFPA books, the ''Fire Protection Handbook'' and ''Introduction to Performance Based Fire Safety'', among their reference works. They also name two NFPA journals, ''Fire Technology'' and the ''NFPA Journal''.<ref name="IFEG-US-05">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.5-7–0.5-10.</ref>

NFPA and SFPE are separate bodies with different roles. The IFEG list them as two distinct organisations that publish fire engineering knowledge, and NIST groups SFPE with the engineering societies rather than with the code and standards organisations.<ref name="IFEG-US-05" /><ref name="NIST-201" /> After its World Trade Center investigation, NIST named both bodies in 2005 for work on standard methods for multi-floor design fire scenarios and on training in computational fire dynamics.<ref name="NIST-212-223">National Institute of Standards and Technology (2005), pp. 212, 223.</ref>

NFPA's codes also offer routes to performance-based design. According to the IFEG, NFPA has not developed an independent performance code but has included a performance option in its building code, NFPA 5000 (2003).<ref name="IFEG-US-02" /> Most US jurisdictions, however, use prescriptive codes and handle alternative designs through equivalency clauses.<ref name="IFEG-US-02" /> An older tool for such equivalency is the Fire Safety Evaluation System, published in NFPA 101A.<ref name="Watts">Watts (2002), pp. 5-129–5-131.</ref> It is a risk-indexing method for showing that certain institutional buildings reach a level of safety equivalent to that of the Life Safety Code.<ref name="Watts" /> US codes leave the decision on what counts as equivalent to the local jurisdiction.<ref name="Watts" />

NFPA 550, the Guide to the Fire Safety Concepts Tree, is one of the most widely cited fault tree formats in fire risk analysis.<ref name="WattsHall-7" /> The tree records the deliberations and professional judgements of an NFPA technical committee and divides fire safety into two branches, preventing fire ignition and managing fire impact.<ref name="Meacham">Meacham (2002), p. 5-158.</ref> One branch or the other must succeed for the fire safety objectives to be met.<ref name="Meacham" /> The Australian handbook for the Fire Safety Verification Method (2020) derives one of its event trees from the manage fire impact branch of this tree.<ref name="ABCB-H-120">Australian Building Codes Board (2020b), p. 120.</ref>

== Limits and common misunderstandings ==

An NFPA document is not binding merely because it exists or is widely cited. In the United States, an NFPA code or standard becomes law only when a jurisdiction adopts it, possibly with changes, and only in the edition that the jurisdiction has chosen.<ref name="Lew-142" /><ref name="Keough-2" /> In New Zealand, for example, Verification Method C/VM2 based its ten design scenarios only partly on those in NFPA 5000, and modified and expanded them to cover further fire events.<ref name="MBIE-121" />

A second limit is scope. NFPA 72 covers the performance of alarm equipment but not where alarms are needed, and most protection criteria of NFPA 13 rest on experience rather than on calculations of fire suppression.<ref name="Keough-2" /><ref name="Fleming-73" /> For fire alarms, Keough and Grill (2005) state that the building code of the jurisdiction with authority over a building defines what alarm requirements apply to it, and when and where.<ref name="Keough-2" />

Fire statistics have limits of their own. Participation in NFIRS and reporting practices are not uniform across regions and sizes of community, so NFIRS may be susceptible to systematic biases.<ref name="Hall-Ahrens-67" /> This is why the NFPA survey is used to calibrate it.<ref name="Hall-Ahrens-67" /> Fires with an unknown characteristic, such as an unreported cause, are usually allocated in proportion to the fires where it is known, which assumes that both groups are alike.<ref name="Hall-Ahrens-67" /> Hall and Ahrens add that, at the time of writing, no one could quantify how far NFIRS deviates from an ideal, representative sample.<ref name="Hall-Ahrens-67" />

Finally, as publisher of the SFPE Handbook, NFPA states in the book's liability notice that the work is published to circulate information and opinion among those concerned with fire and electrical safety.<ref name="DiNenno-iii" /> Neither NFPA nor the authors guarantee the accuracy or completeness of its contents, or accept liability for damage resulting from its use.<ref name="DiNenno-iii" /> They supply information and opinion but do not attempt to render engineering or other professional services.<ref name="DiNenno-iii" /> Where such services are required, the notice advises seeking the help of an appropriate professional.<ref name="DiNenno-iii" />

== See also ==

* [[Fire safety concepts tree]]
* [[Performance-based design]]
* [[Prescriptive design]]
* [[Equivalency]]
* [[Fire scenario]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* DiNenno, P. J., Drysdale, D., Beyler, C. L., Walton, W. D., Custer, R. L. P., Hall, J. R., Jr., & Watts, J. M., Jr. (Eds.). (2002). ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association; Society of Fire Protection Engineers.
* Fahy, R. F., & Proulx, G. (2005). ''Analysis of published accounts of the World Trade Center evacuation'' (NIST NCSTAR 1-7A). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Hyslop, J. S., Kratchman, J., Siu, N., Afshar, C., Najafi, B., Joglar, F., Li, Y., Henneke, D., & Warner, M. (2010). ''Fire probabilistic risk assessment methods enhancements: Supplement 1 to NUREG/CR-6850 and EPRI 1011989'' (NUREG/CR-6850, Supplement 1; EPRI 1019259). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Keough, R. J., & Grill, R. A. (2005). ''Fire alarm systems'' (NIST NCSTAR 1-4C). National Institute of Standards and Technology.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* Ministry of Business, Innovation and Employment. (2013). ''Commentary for Building Code clauses C1–C6 and Verification Method C/VM2''.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Watts, J. M., Jr. (2002). Fire risk indexing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-125–5-142). National Fire Protection Association; Society of Fire Protection Engineers.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Safety Design & Regulation]]

Fire safety objectives

2026-11-02T18:38:31Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''Fire safety objectives''' are the specific fire safety goals that a building or facility is meant to achieve.<ref name="Watts-5-136">Watts (2002), pp. 5-136–5-137.</ref> Typical examples are life safety, property protection, continuity of operations, environmental protection and the preservation of heritage.<ref name="Watts-5-136" /> They state what a fire safety design has to achieve, and so explain why fire safety measures are taken at all.<ref name="VR-1">Van Rossum (2027), §1.</ref> Some objectives are set by law, such as protecting the occupants and preventing fire spread between buildings. Others are chosen by the client or by other stakeholders, for example an insurer.<ref name="IFEG-1-2-7">National Research Council of Canada et al. (2005), pp. 1.2-7–1.2-8.</ref> [[Fire safety engineering]] can itself be defined as applying all fire-related knowledge to achieve the relevant fire safety goals of a project, so the objectives come first.<ref name="VR-1-1">Van Rossum (2027), §1.1.</ref>

Objectives are normally written in general words, such as safeguarding people from an unacceptable risk of injury or illness caused by fire.<ref name="CVM2-37">Ministry of Business, Innovation and Employment (2025b), p. 37.</ref> Before a design can be checked, they are refined into numerical performance criteria, for example a maximum temperature or a limit on fire spread.<ref name="Notarianni-5-52">Notarianni (2002), pp. 5-52–5-53.</ref> Building regulations seldom state how safe is safe enough.<ref name="VR-1-2">Van Rossum (2027), §1.2.</ref><ref name="IFEG-NZ-0-2-5">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.2-5.</ref> In a performance-based design, the objectives and criteria are therefore agreed between the parties involved before the analysis starts.<ref name="IFEG-1-2-2">National Research Council of Canada et al. (2005), p. 1.2-2.</ref><ref name="IFEG-US-0-2-8">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-8.</ref>

== Goals, objectives and criteria ==

In the SFPE Handbook, a common hierarchy of fire safety decisions has five levels, although a particular application may have more or fewer. Objectives form the second level.<ref name="Watts-5-136" /> Above them is the fire safety policy that an organisation adopts to achieve security against fire and its effects. Below them come strategies, each of which contributes wholly or partly to the objectives. The lowest levels are attributes and survey items, which can be measured or estimated in a real building.<ref name="Watts-5-136" /> Broad aims such as fire prevention, fire control and occupant protection usually appear in the introductory sections of building codes and fire safety laws.<ref name="Watts-5-136" />

The terms are not used consistently, and an objective is sometimes simply called a goal. The International Fire Engineering Guidelines (2005) define an objective as the desired overall safety outcome, expressed in qualitative terms.<ref name="IFEG-US-0-5-4">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.5-4–0.5-5.</ref> A functional statement is more specific and states what the building, its systems or its occupants must achieve for an objective to be met. A performance requirement gives the criteria, in engineering terms, by which a trial design is judged.<ref name="IFEG-US-0-5-4" /> In the SFPE Handbook, stakeholders first identify broad goals, such as protecting people and property. These goals are then refined into objectives that can be quantified in engineering terms.<ref name="Notarianni-5-52" />

A simple chain shows how the levels connect, starting from the goal of protecting the occupants. A matching objective may be to keep the gas concentrations in a corridor tenable. The performance criterion then sets the numerical limit against which the expected performance of the design is compared.<ref name="Notarianni-5-52" /> New Zealand's Building Code uses the same ladder of objectives, functional requirements and performance criteria.<ref name="CVM2-2">Ministry of Business, Innovation and Employment (2025b), p. 2.</ref> A report for the US Nuclear Regulatory Commission notes that performance-based designs state their goals explicitly, whereas prescriptive requirements contain them only implicitly.<ref name="NUREG-1-9">Iqbal and Salley (2004), p. 1-9.</ref>

Objectives can be secured in two ways. In a rule-based approach, the design follows predefined rules and limit values, such as legislation, the conditions of an insurer or company rules. Such rules are generic and inflexible, and only partly tailored to the building, its users and its surroundings. In a risk-based or goal-based approach, fire safety is assessed for the specific project, so that more factors can be weighed together. In the Netherlands, such an alternative to the Dutch Buildings Decree (Bbl) is called equivalence. Article 4.7 of the Environment and Planning Act (Omgevingswet) allows it on condition that it achieves at least the same level of fire safety as the prescribed measure that it replaces.<ref name="VR-1" />

== Typical objectives ==

Most fire safety objectives trace back, directly or indirectly, to the protection of people.<ref name="HallAhrens-5-74">Hall and Ahrens (2002), p. 5-74.</ref> The safety of the people in a building when a fire breaks out is one of the most important objectives. Dying in a fire is also perceived as worse than dying in a car accident.<ref name="VR-7">Van Rossum (2027), §7.</ref> Keeping every occupied area completely free of fire effects would be a very conservative and generally unachievable objective. An engineering analysis therefore has to consider what happens to the occupants: how many there are, where they are, how they act and what they can do.<ref name="HallAhrens-5-74" />

Building codes commonly also aim to facilitate the work of the emergency services. Property objectives can concern the building itself, its contents and equipment, or neighbouring buildings. Other common objectives are business continuity and financial viability, corporate and public image, and community interests and infrastructure. Some projects also aim to protect heritage in older or significant buildings, or to limit the release of hazardous materials into the environment.<ref name="IFEG-1-2-7" /> The book ''Introduction to Fire Safety Engineering'' adds limiting the impact of a fire on society. It notes that its own list is an arbitrary and incomplete mix of public and private goals.<ref name="VR-1" />

It is not always clear how something is valued or how its loss should be described.<ref name="Meacham-5-153">Meacham (2002), pp. 5-153–5-154.</ref> For life safety, some people draw the line simply between life and death. Others also count quality of life, pain and suffering, and rehabilitation after an injury.<ref name="Meacham-5-155">Meacham (2002), p. 5-155.</ref> For property, smoke and water damage should be considered as well as damage by heat. For business continuity, a loss of image and market share can follow long after the short-term losses of downtime.<ref name="Meacham-5-153" />

Outside ordinary buildings, the objectives can be quite different. For US nuclear power plants, the primary objectives of fire protection programmes are to minimise both the probability and the consequences of fire. Through defence in depth, these programmes are designed to give reasonable assurance that a fire will not prevent a safe shutdown and that radioactive releases are minimised.<ref name="NUREG-1-1">Iqbal and Salley (2004), p. 1-1.</ref> Defence in depth aims at a balance between preventing fires from starting, detecting and suppressing fires quickly, and limiting the consequences of a fire.<ref name="NUREG-F-20">Iqbal and Salley (2004), p. F-20.</ref>

== Objectives in building regulations ==

[[Building regulations]] set the public objectives that every building must meet, usually in broad words rather than in numbers.<ref name="VR-1-4">Van Rossum (2027), §1.4.</ref><ref name="ABCB-14">Australian Building Codes Board (2020b), p. 14.</ref> In the Netherlands, the explanatory notes to the Dutch Buildings Decree (Bbl) give two aims for its fire safety rules. These are preventing casualties, both injured and dead, and preventing a fire from spreading to another plot. Preserving the building and preventing damage to the environment, monuments or social facilities or interests are explicitly not objectives of the decree. The rules work these aims out in sub-goals, such as keeping the structure standing, limiting fire and smoke spread, and keeping escape and firefighting routes usable.<ref name="VR-1-2" />

In New Zealand, Verification Method C/VM2 (second edition, 2025) relates all its design scenarios to three fire objectives of the Building Code.<ref name="CVM2-7">Ministry of Business, Innovation and Employment (2025b), pp. 7–8.</ref> They are to safeguard people from an unacceptable risk of injury or illness caused by fire, and to protect other property from damage caused by fire. The third is to facilitate firefighting and rescue operations.<ref name="CVM2-58">Ministry of Business, Innovation and Employment (2025b), pp. 58–59.</ref> In Australia, the 2020 handbook to the Fire Safety Verification Method, written for the 2019 edition of the National Construction Code (NCC 2019), summarises the broad fire objectives of that code.<ref name="ABCB-2">Australian Building Codes Board (2020b), p. 2.</ref> They are life safety of occupants, protection of other property, facilities for firefighting and fire safety during construction. The protection of the building itself and its contents is addressed only to a limited extent for some building classes.<ref name="ABCB-27">Australian Building Codes Board (2020b), pp. 27–28.</ref>

The International Fire Engineering Guidelines describe two further systems as they were in 2005. The 2005 National Building Code of Canada was the first edition in an objective-based format, in which every provision serves at least one stated objective. Its objectives are worded as limiting the probability of undesirable situations, because a code cannot prevent them completely. The risk that remains after the code is complied with is regarded as the acceptable risk.<ref name="IFEG-CA-0-2-2">National Research Council of Canada et al. (2005), Part 0 (Canada), p. 0.2-2.</ref> For the United States, the guidelines note that choosing the intended level of performance is a value judgement that should ultimately be made by policy makers rather than by designers.<ref name="IFEG-US-0-2-6">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-6.</ref>

The overall level of safety is rarely stated in numbers.<ref name="ABCB-14" /> The Dutch rules do not lay down how many deaths and injuries are acceptable, or how large the risk of fire spread to a neighbouring plot may be. Their measurable limits apply to the measures instead, such as walking distances, minutes of fire resistance and compartment areas. These limits grew partly from consensus and partly from history, not from a quantified goal.<ref name="VR-1-2" /> The 2005 guidelines note that in New Zealand, too, the level of safety of the Building Code is not always stated explicitly, which can make its requirements hard to interpret.<ref name="IFEG-NZ-0-2-5" />

== Objectives of owners and other stakeholders ==

In a performance-based project, the objectives are agreed in the fire engineering brief (FEB), the process in which the stakeholders set down the basis of the analysis.<ref name="IFEG-1-2-2" /><ref name="IFEG-1-2-7" /> The International Fire Engineering Guidelines suggest first identifying the objectives of each stakeholder, which may differ. These are then divided into building regulatory, other regulatory and non-regulatory objectives. Other regulatory objectives come from laws on matters such as the environment, occupational health and safety, the fire services, dangerous goods and planning. Non-regulatory objectives are set by the client or other stakeholders, for example to limit damage to the structure, contents and equipment.<ref name="IFEG-1-2-7" />
[[File:fse-fire-safety-objectives-v1.svg|thumb|upright=1.5|alt=Building law, other law and stakeholders contribute distinct objectives to one project.|Fire-safety objectives arise from different requirements and stakeholder goals. Based on National Research Council of Canada et al. (2005), pp. 1.2-7–1.2-8.]]

Complying with the code and protecting an owner's assets are not the same thing. Some owners do not realise that code compliance can differ significantly from protecting their building, process, contents or other assets of value. Such differences matter when tolerable damage and acceptance criteria are chosen, so the interested and affected parties must be involved.<ref name="Meacham-5-155" /> For New Zealand, the 2005 guidelines explain that the Building Act 2004 does not require anyone to exceed the performance criteria of the Building Code, so doing so is the owner's choice.<ref name="IFEG-NZ-0-3-6">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-6.</ref>

Clients also have objectives that are not about fire but still affect fire safety. Examples are increased security, natural lighting, an open-plan layout, new materials, energy efficiency, flexibility for future uses and low life-cycle costs.<ref name="IFEG-1-2-7" /> In the New Zealand part of the guidelines, the fire engineer is responsible for ensuring that such objectives do not stop the design from meeting the fire requirements of the Building Code.<ref name="IFEG-NZ-0-3-3">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-3.</ref> The engineer should also explain to the client the effect of adopting further objectives or not, and decline instructions where the objectives are unacceptable.<ref name="IFEG-NZ-0-4-1">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.4-1.</ref> In Australia, the 2020 handbook likewise asks for client and end-user objectives to be identified early.<ref name="ABCB-22">Australian Building Codes Board (2020b), p. 22.</ref>

Stakeholders do not always value the same outcomes in the same way. Some people accept a higher risk to firefighters, who take on risk as part of their job, if this lowers the risk to the public, while others do not.<ref name="Notarianni-5-46">Notarianni (2002), p. 5-46.</ref> Stakeholders may want to protect historic features or to avoid business interruption, and those with different values may see these needs differently. The SFPE Handbook therefore advises identifying where value judgements enter a design and making these assumptions explicit.<ref name="Notarianni-5-52" />

== From objectives to acceptance criteria ==

Objectives are too broad to be checked directly, so [[Acceptance criteria|acceptance criteria]] are set for the analysis.<ref name="IFEG-CA-0-2-2" /> The criteria must suit the objectives, the performance requirements and the analysis methods. They must also be numerical, unless the analysis is qualitative, and realistic: zero risk is not an appropriate criterion.<ref name="IFEG-1-2-25">National Research Council of Canada et al. (2005), pp. 1.2-25–1.2-26.</ref> In the ten-step design process of the SFPE Handbook, the scope, goals and objectives are defined before the performance criteria are developed. Design fire scenarios, candidate designs and their evaluation follow after that.<ref name="Notarianni-5-52" />

The guidelines give typical criteria for each general objective. Protecting occupants can be judged by the margin between the available and the required escape time, and by the smoke layer height. Other occupant criteria are the temperature and radiant heat of the hot layer, the smoke density and the carbon monoxide level. Facilitating the fire services can be judged by radiant heat, structural failure, water supply and resources at the fire scene. Protecting adjacent property uses the radiant heat from the fire and flame impingement, while limiting damage and keeping a business running use monetary loss, smoke release and corrosive gases. Environmental objectives use the toxicity of the fire gases, the containment of firefighting water and the expected risk to plants and animals.<ref name="IFEG-1-2-25" />
[[File:fse-fire-safety-objectives-v2.svg|thumb|upright=1.5|alt=Objective, exposed group, scenario, criterion and evidence form a traceable assessment chain.|Objectives must be translated into assessable criteria and evidence. Based on National Research Council of Canada et al. (2005), pp. 1.2-25–1.2-26.]]

Regulations sometimes fix the numbers themselves. In New Zealand, the objective of protecting other property is backed by limits on the radiation received from a fire. The radiation may not exceed 30 kW/m² at the boundary of the property, or 16 kW/m² at 1 m beyond it. These values belong to the New Zealand Building Code as applied in C/VM2 (second edition, 2025).<ref name="CVM2-43">Ministry of Business, Innovation and Employment (2025b), p. 43.</ref> In an absolute assessment, the values may instead be agreed in the fire engineering brief, and they should allow for uncertainty and safety factors.<ref name="IFEG-1-2-25" />

Two approaches are used to judge whether a design meets its objectives.<ref name="IFEG-1-2-21">National Research Council of Canada et al. (2005), p. 1.2-21.</ref> In a comparative approach, the trial design is compared with an otherwise identical building that follows the prescriptive rules.<ref name="IFEG-1-2-21" /> The same criteria are used for both, and the trial design should perform at least as well.<ref name="IFEG-1-2-25" /> In an absolute approach, the results are matched directly against the objectives using the agreed criteria.<ref name="IFEG-1-2-21" /> In Australia, the Fire Safety Verification Method compares the design with a reference building that follows the deemed-to-satisfy provisions. This can make the outcome less sensitive to the choice of inputs and methods.<ref name="ABCBDS-i">Australian Building Codes Board (2020a), p. i.</ref>

== How objectives guide the design ==

The Australian handbook defines a [[Fire safety strategy|fire safety strategy]] as a combination of physical and human measures, including maintenance and management, specified to achieve the nominated fire safety objectives.<ref name="ABCB-140">Australian Building Codes Board (2020b), p. 140.</ref> The design process normally starts by defining the relevant objectives, of the building code and any others, and then develops the strategy. The handbook describes fire safety engineering as a logical sequence from objectives and performance requirements to the strategy, fire scenarios, detailed analysis and the decision on compliance.<ref name="ABCB-20">Australian Building Codes Board (2020b), p. 20.</ref> The documented strategy should include a summary of the fire safety objectives.<ref name="ABCB-31">Australian Building Codes Board (2020b), p. 31.</ref>

Strategies link the objectives to concrete measures. Examples are ignition prevention, limitation of combustibles, compartmentation, detection and alarm, suppression and the protection of exposed people or things. A matrix of objectives against strategies shows how important each strategy is for each objective.<ref name="Watts-5-136" /> A single system can serve several objectives: smoke and heat venting is designed to help people escape, to let firefighters see the seat of the fire, and to reduce property damage.<ref name="Cooper-3-219">Cooper (2002b), p. 3-219.</ref> How well a system serves an objective depends on two factors. Efficacy is the degree to which it achieves a design objective when it works as specified, and reliability is the probability that it does work as specified.<ref name="ABCBDS-C4">Australian Building Codes Board (2020a), Data Sheet C4, p. 125.</ref>

The [[Fire safety concepts tree|fire safety concepts tree]], a diagram based on the judgements of an NFPA technical committee, starts from the fire safety objectives at its top. Below them, it splits into two branches: preventing fire ignition and managing the fire impact. One branch or the other must succeed for the objectives to be met. Ignition is prevented by controlling heat sources, their interaction with fuel, and the fuel itself. Fire impact is reduced either by managing the fire itself or by managing what is exposed to it. If ignition is not prevented, the tree helps to evaluate whether the systems of the building can manage the fire impact.<ref name="Meacham-5-158">Meacham (2002), p. 5-158.</ref>
[[File:fse-fire-safety-objectives-v3.svg|thumb|upright=1.5|alt=Fire-safety objectives branch into preventing ignition and managing fire impact.|Prevention and impact management provide complementary paths towards objectives. Based on Meacham (2002), p. 5-158.]]

In New Zealand, C/VM2 (second edition, 2025) tests a design against ten design scenarios that must each be satisfied separately. Each scenario is tied to one or more of the Building Code objectives.<ref name="CVM2-7" /> One scenario checks that the failure of a critical part of the fire safety system does not cause the design to miss those objectives. Each key system, such as smoke management or a fire door, is assumed to fail in turn, and the design is changed if the occupants could then no longer escape safely. Sprinklers and automatic fire alarms installed to a recognised standard are treated as reliable enough to be exempt.<ref name="CVM2-58" />

== Limits and common misconceptions ==

Fire safety objectives do not aim at absolute safety. For New Zealand and the United States, the International Fire Engineering Guidelines state that absolute safety and zero risk are not achievable. The accepted risk takes into account what the community expects and what safety costs the community.<ref name="IFEG-NZ-0-2-5" /><ref name="IFEG-US-0-2-8" /> The Australian handbook adds that removing all risk would bring the fire safety strategy into conflict with the function and use of the building.<ref name="ABCB-27" /> Objectives therefore aim at an acceptable or tolerable level of [[Fire risk|fire risk]], not at the absence of risk.<ref name="IFEG-CA-0-2-2" /><ref name="ABCB-27" />

Deriving that level from the regulations is difficult, because their actual outcomes differ widely between types of building. In the Netherlands, the chance of dying in a fire per hour of stay is much greater in a residential building than in an assembly building. Yet the requirements for fire detection are stricter for assembly buildings. For an engineering approach, the required performance or the accepted residual risk must therefore be agreed in advance, for example by comparison with a reference situation that follows the rules.<ref name="VR-1-2" /> The Netherlands has no risk-based limit values, which the book names as a drawback of quantitative analysis there.<ref name="VR-1-4" />

Objectives also carry values and uncertainty. The SFPE Handbook (2002) notes that no significant work has been done to identify what fire safety is trying to achieve, so lists of objectives are very subjective.<ref name="Watts-5-136" /> Few studies show how society values fire safety risks at the level needed for performance-based trade-offs.<ref name="Notarianni-5-46" /> Uncertainty arises in the science, in human behaviour, in perceptions of risk and values, and in decision making itself. Some people are risk tolerant, while others are risk averse.<ref name="Meacham-5-160">Meacham (2002), p. 5-160.</ref>

Meeting one objective does not mean meeting the others. Two designs may be equivalent for life safety but not for property protection, business interruption or structural collapse. The conditions behind the objectives also change over the life of a building, because its use, its occupants and even the fire service may change.<ref name="Notarianni-5-46" /> The fire safety of a building depends on its fire safety system continuing to work and on management limits, such as fuel loads and free escape routes, being respected. When a building is altered or its use changes, the existing fire engineering evaluation may have to be re-examined to see whether it still applies.<ref name="IFEG-NZ-0-3-8">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-8.</ref>

== See also ==

* [[Qualitative design review]]
* [[Performance-based design]]
* [[Prescriptive design]]
* [[Equivalency]]
* [[Fire scenario]]
* [[Fire safety management]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr. (2002). Fire risk indexing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-125–5-142). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Safety Design & Regulation]]

Fire risk

2026-11-02T18:38:25Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''Fire risk''' is the potential for a fire to cause unwanted, adverse consequences to human life, health, property or the environment.<ref name="WH-5-3">Watts and Hall (2002), p. 5-3.</ref> It brings together three questions: what could happen, how bad it would be, and how likely it is.<ref name="WH-5-1">Watts and Hall (2002), pp. 5-1–5-2.</ref> A fire risk therefore depends both on the consequences of possible fires and on the likelihood that they occur. It describes the uncertainty of a loss, not a loss that is certain to happen.<ref name="WH-5-1" /> Every decision related to fire safety is in effect a fire risk decision, whether or not it is treated as one.<ref name="WH-5-1" />
[[File:fse-fire-risk-v1.svg|thumb|upright=1.5|alt=What could happen, how likely and how severe lead to a risk evaluation.|Fire risk combines event scenarios, likelihood and consequences. Based on Watts and Hall (2002), pp. 5-1–5-3 and Meacham (2002), pp. 5-154–5-156.]]

Zero risk is not an achievable goal, because no technology is completely reliable and natural events such as lightning and earthquakes can also cause fires.<ref name="WH-5-4">Watts and Hall (2002), p. 5-4.</ref> The practical questions are how large the remaining risk is and whether it is acceptable. Accepting a level of risk requires a value judgement, and people make such judgements in different ways.<ref name="WH-5-1" /> Fire risk is estimated from [[Fire statistics|fire statistics]], usage data and laboratory tests, and the result is then judged for its acceptability.<ref name="HallAhrens-5-65">Hall and Ahrens (2002), p. 5-65.</ref><ref name="WH-5-3" />

== Hazard, consequence and probability ==

A hazard is a chemical or physical condition that has the potential to cause damage to people, property or the environment.<ref name="WH-5-3" /> An analysis of what could happen and how bad it would be, without considering how likely it is, is called a fire hazard analysis. A fire risk analysis adds the likelihood. A sequence of events that ends in a fire loss is called a scenario.<ref name="WH-5-1" /> For a whole building, the fire risk is the full spread of possible events and their consequences, not the outcome of one scenario.<ref name="WH-5-3" />

Consequences describe how bad a fire would be if it happened. They range from deaths and damage to property to intangible losses such as business interruption, environmental damage and the destruction of cultural objects. A consequence can be direct, such as damaged property, or indirect, such as a company that is out of business for several days. It can also be objective, such as a replacement cost, or subjective, such as the pain and suffering of an injury.<ref name="WH-5-1" /> In building fire risk analysis, the main things of value are life safety, property, business continuity, the environment and heritage.<ref name="Meacham-5-153">Meacham (2002), pp. 5-153–5-154.</ref>

Risk is usually estimated by combining the probability that an event occurs with the consequence of the event if it does occur.<ref name="WH-5-3" /> The terminology is not consistent: a committee of the Society for Risk Analysis found 17 different definitions of risk.<ref name="WH-5-3" /> The SFPE Handbook also describes fire risk as the possibility of an unwanted outcome in an uncertain situation, where fire may cause loss or harm to something that is valued.<ref name="Meacham-5-153" /> A related term is the fire safety level, which the Australian Fire Safety Verification Method handbook (2020) calls the reciprocal of fire risk: when the risk to occupants falls, the safety level rises.<ref name="ABCB-140">Australian Building Codes Board (2020b), p. 140.</ref>

== Frequency and probability ==

A frequency states how often an event occurs in a period, such as the number of fires per year. On its own it is not a probability, because the number of possible occurrences is also needed.<ref name="Meacham-5-159">Meacham (2002), p. 5-159.</ref> In a hypothetical example, 20 fires a year in toasters that are switched on 20 million times a year give a probability of one in a million per start.<ref name="Meacham-5-159" /> Fire incident data therefore have to be combined with usage or exposure data, such as the number of appliances in use or the floor area of a type of building.<ref name="HallAhrens-5-65" />

There are two views of probability. In the frequency view, probability is the proportion of the time that an event occurs in the long run. In the subjective view, it measures how strongly a person believes that an event will occur.<ref name="WH-5-3" /> Fires are relatively rare, and buildings and their contents change over time, so past losses are a limited guide to future ones. This is a strong argument for using subjective probabilities, based on current knowledge and judgement, in building fire risk analysis.<ref name="Meacham-5-159" />

The amount of available data differs widely. For US homes there are very many recorded fires with limited detail, while for US nuclear power plants there are far fewer fires but much more detail on each. For a single existing building there are very few fires at all. In fire safety engineering, risk analysis is therefore mostly used for an application or a class of facility with a considerable fire loss history.<ref name="WH-5-3" />

== Typical values ==

The frequency of fire depends strongly on the use of a building. In British Standards Institution data from 2001, quoted in the International Fire Engineering Guidelines (2005), a dwelling had about 0.003 fire starts per year and an office about 0.006. Schools and industrial buildings had about 0.04, entertainment venues about 0.12 and hospitals about 0.3 fire starts per building per year. The guidelines warn that such values may have changed with new technologies and materials.<ref name="IFEG-3-2-2">National Research Council of Canada et al. (2005), p. 3.2-2.</ref> Finnish data show that the number of fires per square metre falls as buildings get larger, while the number per building generally rises with floor area.<ref name="IFEG-3-2-3">National Research Council of Canada et al. (2005), p. 3.2-3.</ref>

Risk studies often sort frequencies into broad classes. One example in the SFPE Handbook calls events anticipated if they occur more often than once in 100 years. Events are unlikely between once in 100 and once in 10,000 years, and extremely unlikely between once in 10,000 and once in a million years. Rarer events are beyond extremely unlikely. Frequencies should be counted for a given loss rather than for a single scenario: 30 scenarios that each occur once in 10 million years together occur three times in a million years.<ref name="Meacham-5-166">Meacham (2002), pp. 5-166–5-167.</ref>

Reliability values are typical inputs as well. In reported US home fires, roughly one-third of smoke alarms were not working, but a general study of home installations found only one-fifth not working. Data from unreported fires suggest that the main reason is that working alarms keep many fires so small that the fire service is never called. Reported US fires suggest that sprinklers do not operate in one-sixth to one-fifth of the fires large enough to activate them, yet their real reliability could be well over 90 %.<ref name="HallAhrens-5-72">Hall and Ahrens (2002), p. 5-72.</ref>

== Individual and societal risk ==

Risk to people is often expressed in two complementary ways. [[Individual risk]] is the probability of injury or death to a person at a specified location relative to a fire or explosion source. It can be drawn as contour lines that connect points of equal risk, regardless of whether anyone is actually present there.<ref name="Barry-5-210">Barry (2002), p. 5-210.</ref> In the Australian Fire Safety Verification Method handbook (2020), individual risk is the frequency at which a person may be expected to suffer a given level of harm from a fire in the building.<ref name="ABCB-22">Australian Building Codes Board (2020b), p. 22.</ref>

[[Societal risk]] takes into account the likelihood of fires or explosions that cause multiple casualties. It is often shown as an F-N curve, which plots the frequency of events that exceed a given number of fatalities, N, against that number.<ref name="Barry-5-210" /> Such a curve requires the population at risk, the likelihood that people are present and the reliability of measures such as evacuation to be defined.<ref name="Barry-5-211">Barry (2002), p. 5-211.</ref> Barry (2002) describes these measures for the chemical process industries, where most calculations of risk to people are based on fatalities.<ref name="Barry-5-211" />
[[File:fse-fire-risk-v2.svg|thumb|upright=1.5|alt=Location-based individual contours contrast with cumulative frequency for multiple casualties.|Individual and societal risk answer different questions. Based on Barry (2002), pp. 5-210–5-211.]]

The two measures answer different questions. Individual risk shows how the risk to one person varies from place to place, while societal risk shows how often losses of many lives can occur.<ref name="Barry-5-210" /> Single-value risk indices, such as an annual predicted fatality rate, are easy to understand and useful for comparing design options. A ranking of the events that contribute most to the total helps to focus risk reduction.<ref name="Barry-5-211" /> In Australia, the Fire Safety Verification Method Standard 2022 accepts the deemed-to-satisfy provisions of the National Construction Code as reflecting societal expectations, including on individual and societal risk.<ref name="ABCB2022-7">Australian Building Codes Board (2022), p. 7.</ref>

== Acceptable risk ==

Acceptable risk is a value judgement applied to a chosen scale for measuring risk. It needs two prior decisions: how risk is measured, and whose views on acceptability count. For a practising engineer, acceptable risk is usually the risk acceptable to the client, while for an authority it is meant to be acceptable to society or to a particular community. A universally acceptable level of fire risk does not exist, because it depends on the problem and on the person judging it.<ref name="WH-5-4" />

People judge the same risk in different ways. Experts mainly weigh the calculated reduction in fire risk, while ordinary people also weigh costs and other needs. Enforcers act on behalf of society, and managers such as builders are most directly affected by the costs.<ref name="WH-5-1" /> The reduced fire risk of a home sprinkler system, for example, appears to be valued less by the average citizen than the benefit of a new car.<ref name="WH-5-1" /> Risks that are objectively equal are also perceived differently: people prefer certain over uncertain, familiar over unfamiliar, voluntary over involuntary and ordinary over dramatic risks.<ref name="WH-5-3" /> Dying in a fire is perceived as worse than dying in a car accident, and most people who die in fires die at home.<ref name="VR-7">Van Rossum (2027), §7.</ref>

Reducing fire risk may even increase other risks, as with the potential damage to the ozone layer from halon extinguishing agents. The goal that comes closest to zero risk is risk as low as is technically possible. In fire protection engineering, this may mean accepting the residual risk after all identified risk reduction measures have been adopted. A complication is that this residual risk may then be perceived as zero, although a non-zero risk remains.<ref name="WH-5-4" /> In Australia, workplace health and safety legislation also requires safe design, which a code of practice defines as eliminating risks to health and safety or, if this is not [[ALARP|reasonably practicable]], minimising them.<ref name="ABCB-25">Australian Building Codes Board (2020b), p. 25.</ref>

Building regulations rarely state an acceptable risk in numbers. The Australian Fire Safety Verification Method Standard 2022 notes that the National Construction Code contains no specific safety targets. A design assessed with this method must therefore be at least equivalent to the deemed-to-satisfy provisions.<ref name="ABCB2022-7" /> It adds that a full quantitative probabilistic risk assessment would ideally be used, but the tools and data for it are not included. The method instead permits a simple deterministic comparison of available and required escape times, with additional checks.<ref name="ABCB2022-18">Australian Building Codes Board (2022), p. 18.</ref>

In the Netherlands, where no risk-based limit values exist, the residual risk can be expressed as an acceptable probability of failure. One way to set it is by comparison with a reference situation that follows the rules.<ref name="VR-1-2">Van Rossum (2027), §1.2.</ref><ref name="VR-1-4">Van Rossum (2027), §1.4.</ref> In performance-based design, deciding which consequences matter is often described as setting fire safety goals, [[Fire safety objectives|fire safety objectives]] and criteria.<ref name="Meacham-5-155">Meacham (2002), p. 5-155.</ref>

== Fire statistics as evidence ==

Fire incident data show how often fires start and how severe they are. In the United States, the national fire incident reporting system collects roughly a million fires a year, but only about half of the fires reported to fire departments. A separate survey of fire departments is therefore used to scale the data up to national estimates. Fires with an unknown cause must be allocated over the known causes. If they are ignored while the share of unknowns falls, every known cause can appear to grow although the total number of fires stays the same.<ref name="HallAhrens-5-67">Hall and Ahrens (2002), pp. 5-67–5-68.</ref>

Not every fire appears in these statistics. Fires handled by the occupants or by private fire brigades are not reported, and fires in buildings with sprinklers or good detection are more likely to be controlled on site. Anecdotes show the range of fires that can happen but cannot be used to estimate rates or probabilities. Detailed databases that are not statistically representative can also mislead, so analysts should not give up statistical validity for detail.<ref name="HallAhrens-5-69">Hall and Ahrens (2002), pp. 5-69–5-70.</ref>

Data on the reliability of fire protection systems are scarce.<ref name="HallAhrens-5-69" /> Expert estimates tend to rate reliable systems even higher and unreliable systems even lower than they really are. Inspection and testing records usually come from well-maintained properties, so they show better reliability than typical buildings achieve. They can also miss short-lived failures, such as a door blocked open.<ref name="HallAhrens-5-71">Hall and Ahrens (2002), p. 5-71.</ref>

== Assessing and reducing fire risk ==

Fire risk analysis is a structured approach to decision making under uncertainty. A general procedure identifies the fire hazards, estimates their consequences and probabilities, identifies options to control them, estimates how each option changes the risk, and selects the protection.<ref name="WH-5-4" /> Methods of [[Fire risk assessment|fire risk assessment]] range from checklists and written recommendations through risk indexing to probabilistic methods.<ref name="WH-5-4" /> Checklists and written recommendations do not quantify risk: a design passes if it follows them, and the residual risk is never evaluated.<ref name="WH-5-5">Watts and Hall (2002), p. 5-5.</ref>

A risk matrix sorts hazards by classes of consequence and likelihood, and each cell can record whether such risks are acceptable or how they should be reduced. Probabilistic methods are the most informative, because their results can be traced back through explicit assumptions, data and relationships. Common tools are event trees, which follow the possible outcomes after an initiating event in time order, and fault trees, which show the combinations of system states that lead to an outcome.<ref name="WH-5-5" />

Risk can be reduced at several points in the chain from cause to consequence. The SFPE Handbook describes a causal sequence from an initiating event through its outcome and the exposure of people or property to the final consequences. The sequence can be interrupted at each of these points, by blocking the event, the outcome, the exposure or the consequence.<ref name="Meacham-5-157">Meacham (2002), p. 5-157.</ref> In the chemical process industries, some measures reduce how often incidents occur, such as preventive maintenance, control of ignition sources and operator training. Others reduce how severe they are, such as gas and fire detection, fireproofing of steel and water sprays.<ref name="Barry-5-211" />
[[File:fse-fire-risk-v3.svg|thumb|upright=1.5|alt=Ignition, fire development, exposure and consequences offer different intervention points.|Risk reduction can act at several points in the fire scenario. Based on Meacham (2002), pp. 5-157–5-159 and Barry (2002), p. 5-211.]]

Measures only reduce risk if they work when they are needed. Typical reliability questions are whether the battery in a smoke alarm works, whether a sprinkler valve is open and whether a fire door is blocked open.<ref name="WH-5-6">Watts and Hall (2002), p. 5-6.</ref> A US Nuclear Regulatory Commission guide lists causes of sprinkler failure. Examples are a closed water supply valve, an empty tank and a fire pump that fails to start, for instance after a power failure.<ref name="NUREG-10-2">Iqbal and Salley (2004), p. 10-2.</ref> Failures can also share a common cause, as when a failure of the fire detection system stops a smoke control system from working as intended.<ref name="ABCBDS-C4">Australian Building Codes Board (2020a), Data Sheet C4, p. 131.</ref>

== Uncertainty and variability ==

Fire risk estimates are always uncertain. Unwanted combustion is perhaps the least predictable common physical phenomenon, and uncertainty analysis should underpin the choice of safety factors and safety margins. This concerns the uncertainty of the engineer about how large a risk is, not the uncertainty of a potential victim about whether a fire loss will occur.<ref name="WH-5-6" /> A totally objective way to measure fire risk does not exist, because defining the problem, collecting data and combining information all involve subjective judgements.<ref name="WH-5-3" />

Uncertainty and variability are different things. It may not be known how many people will be exposed, which is uncertainty, while the people who are exposed differ from each other, which is variability.<ref name="Meacham-5-159" /> Scientific uncertainties come from theories and models, from data and inputs, from limits of the calculation, from the level of detail and from how well a model represents reality. Further uncertainty lies in human behaviour, in perceptions of risk and values, and in decision making itself.<ref name="Meacham-5-160">Meacham (2002), p. 5-160.</ref>

Calculations can hide much of this uncertainty. Fire models give single values, such as a detector activation time of 121 s, although the real time may be longer or shorter. One widely used egress model assumes that all occupants are readily mobile and start leaving as soon as they hear an alarm, which experience shows is often not the case. In a full uncertainty analysis, only the inputs that could change the decision on whether a design is acceptable, a change called switchover, need detailed quantitative treatment.<ref name="Notarianni-5-43">Notarianni (2002), pp. 5-43–5-44.</ref>

Design practice also handles variability and uncertainty in simpler ways. The Dutch national annex to Eurocode 1 (NEN-EN 1991-1-2/NB), for example, gives both average fire loads and 80 % fractiles for a more conservative approach. An 80 % fractile is a value that the actual fire load does not exceed in 80 % of cases.<ref name="VR-8-5">Van Rossum (2027), §8.5.</ref> An escape time analysis keeps a safety margin between the available and the required escape time, because many of the inputs are uncertain. The more reliable the inputs are, the smaller the margin needs to be.<ref name="VR-7-1">Van Rossum (2027), §7.1.</ref>

== See also ==

* [[Event tree analysis]]
* [[Fault tree analysis]]
* [[Quantitative risk assessment]]
* [[Reliability of fire protection systems]]
* [[Uncertainty analysis]]
* [[Fire safety concepts tree]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-176–5-213). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Risk Analysis]]

Fire investigation

2026-11-02T18:38:14Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''Fire investigation''' is the examination of a fire after the event to establish where and how it started, how it developed and how the building, its fire protection and its occupants were affected. Writing on spontaneous ignition in the SFPE Handbook, Gray notes that fire prevention and fire cause investigation both need to identify the critical conditions for ignition, before and after the event respectively.<ref name="Gray-2-211">Gray (2002), p. 2-211.</ref> Hall and Ahrens list the reconstruction of major fires among the engineering analyses that require input data on fires.<ref name="HA-5-65">Hall and Ahrens (2002), p. 5-65.</ref> The Society of Fire Protection Engineers likewise counts post-fire investigation and analysis as part of fire protection engineering.<ref name="IFEG-US-0.3-1">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-1–0.3-2.</ref>

Fire investigation matters because its findings explain why fires start and why protection succeeds or fails, and they can lead to changes in how buildings are designed, built and regulated. The US investigation of the World Trade Center disaster of 2001, for example, was meant to serve as the basis for improvements in building practice and revisions to codes and standards.<ref name="NIST-xxxv">National Institute of Standards and Technology (2005), pp. xxxv–xxxvi.</ref> Investigations depend on the evidence that survives, and large fires destroy much of it. Fire loss statistics from many sources show an unknown cause more often in fires with multimillion-dollar losses than in smaller fires, probably because more evidence is lost.<ref name="Gray-2-211" />

== Purpose and scope ==

Investigations differ in purpose and authority. The US National Institute of Standards and Technology (NIST) investigated the World Trade Center disaster to determine why and how the buildings collapsed. It also asked why injuries and fatalities were high or low depending on location, and examined the procedures used in design, construction, operation and maintenance and the parts of codes and standards that warranted revision.<ref name="NIST-xxxv" /> NIST is a non-regulatory agency whose investigations focus on fact finding. It has no authority to find fault or negligence, and its reports may not be used in lawsuits for damages.<ref name="NIST-xxxv" />

Other investigations can have legal consequences. Van Rossum notes that an investigation after a fire disaster may show that the cause lies in demonstrably wrong advice, below the knowledge and skill that could be expected at the time. In that case the adviser can be prosecuted.<ref name="VR-2.5">Van Rossum (2027), §2.5.</ref>

For the World Trade Center buildings, the New York City fire department provided NIST with 112 records of its Bureau of Fire Investigation from 1977 to 2001. It also provided 397 operational fire reports from 1970 to 2001, all on standardised forms. NIST's review of earlier fires included, for example, a fire on 14 February 1975 on the 11th floor of WTC 1, one of the two towers. It spread through unprotected floor openings in utility closets and caused damage from the 10th to the 19th floor.<ref name="Kuligowski-1">Kuligowski et al. (2005), p. 1.</ref>

Large investigations break the work into specific questions. For the sprinklers, standpipes and hoses of the towers, the NIST study first documented their design and installation and compared them with the codes and standards of record. It then estimated their capacity under normal conditions with hydraulic calculations.<ref name="Hopkins-xxxii">Hopkins et al. (2005), p. xxxii.</ref> Only then did it ask what happened to the systems at each major event, how their performance was affected and at what point in the sequence they were lost.<ref name="Hopkins-xliii">Hopkins et al. (2005), p. xliii.</ref>
[[File:fse-fire-investigation-v1.svg|thumb|upright=1.5|alt=Questions guide evidence collection, reconstruction, modelling and findings with uncertainty.|Fire investigation reconstructs events from evidence and explicit inference. Based on Hopkins et al. (2005), pp. xxxi–xxxii and Hall and Ahrens (2002), pp. 5-65–5-67.]]

== Evidence and how it is gathered ==

Fire investigators normally read the path and intensity of a fire from telltale signs left in the building. In the World Trade Center towers this was impossible because neither building remained, so NIST relied on what may have been the most photographed disaster in history.<ref name="Gann-xxxviii">Gann, Hamins, et al. (2005), p. xxxviii.</ref> In each photograph and video frame, every window was coded for fire, smoke and whether the window was still in place, which produced detailed timelines of fire spread.<ref name="Gann-xxxviii" /> NIST also reviewed tens of thousands of pages of documents, interviewed over a thousand people and analysed 236 pieces of steel recovered from the wreckage.<ref name="NIST-xxxvi">National Institute of Standards and Technology (2005), p. xxxvi.</ref>

Time links the evidence together. NIST describes time as the unifying factor in combining photographs, videos, survivor accounts, emergency calls and communications among emergency responders.<ref name="NIST-82">National Institute of Standards and Technology (2005), p. 82.</ref> Images were timed by matching them to one well-defined event, the impact of the second aircraft at 9:02:59 a.m., and then to other events visible in several images. In all, 3,032 photographs and 2,673 video clips were timed to within 3 seconds or better, and the uncertainty of each time was logged.<ref name="NIST-83">National Institute of Standards and Technology (2005), pp. 83–84.</ref>

Physical evidence needs careful interpretation. NIST found that the primer paint on the towers' steel cracked in a "mud cracking" pattern above 250 °C. Deformation and the environment can also cause such cracks, so their absence shows that the steel stayed below 250 °C, but their presence does not prove high temperature.<ref name="Gayle-94">Gayle et al. (2005), p. 94.</ref> The method could not tell whether the heating happened before or after the collapse. The panels examined were also only 3% of the perimeter columns on the fire floors and could not be treated as representative of the others.<ref name="Gayle-xli">Gayle et al. (2005), p. xli.</ref>

People are a source of evidence as well. For the evacuation of the towers, NIST gathered over 1,000 new interviews with survivors, over 700 published interviews, emergency calls and transcripts of emergency communications.<ref name="Averill-iii">Averill et al. (2005), p. iii.</ref> Proulx notes that fire victims may have difficulty reporting accurately how long they waited before starting to evacuate, but that interview techniques can give acceptable estimates.<ref name="Proulx-3-349">Proulx (2002), p. 3-349.</ref> The causes of death in fires have been studied through pathological investigations of fire victims.<ref name="Purser-2-85">Purser (2002), p. 2-85.</ref> Carbon monoxide combines with haemoglobin in the blood to form carboxyhaemoglobin. In the Strathclyde study of fire deaths in the United Kingdom, 54% of those who died had a lethal level of it, and 69% had a level capable of causing incapacitation.<ref name="Purser-2-100">Purser (2002), p. 2-100.</ref>

== Establishing the cause ==

To describe how a fire started, investigators separate the parts of the ignition sequence. US fire incident coding distinguishes the form of heat of ignition and the equipment involved, which together describe the [[ignition source]], from the form and type of material first ignited. It also records the ignition factor that brought heat and fuel together, and the area of origin.<ref name="HA-5-68">Hall and Ahrens (2002), p. 5-68.</ref> The New York fire department's structural fire form recorded the same kind of information, and it called the ignition factor the cause.<ref name="Kuligowski-2">Kuligowski et al. (2005), p. 2.</ref>

Some causes leave characteristic traces. Spontaneous ignition of stacked material, such as cotton, woodchips or oily rags, starts in the well-insulated centre of the pile. Such a pile can therefore be charred or burnt to ash inside while looking almost untouched outside.<ref name="Gray-2-212">Gray (2002), p. 2-212.</ref><ref name="Gray-2-224">Gray (2002), p. 2-224.</ref> Hot gases escape along the path of least resistance and form "chimneys" of charred material, and several chimneys are the norm. Gray reports that finding more than one heavily charred area has led to wrongful charges of arson, based on the myth that more than one seat of fire means the fire was started deliberately.<ref name="Gray-2-225">Gray (2002), p. 2-225.</ref>

Gray lists the practical factors that make spontaneous ignition more likely, including a large body of material, high surrounding temperatures, thermal insulation, porous or fibrous material and a high stacking temperature.<ref name="Gray-2-224" /> Material left undisturbed for longer than usual is also reason for suspicion. In one case a warehouse of cottonseed meal burned down after a transport strike had left the meal in place far longer than normal.<ref name="Gray-2-225" /> In another, an instant-noodle factory burned down after new management sped up the production line, so that the noodles were packed hotter than before. Laboratory tests and calculations then showed that the packed pallets could ignite spontaneously at the new temperatures but not at the old ones.<ref name="Gray-2-226">Gray (2002), pp. 2-225–2-226.</ref>

Gray advises caution about the timing of such fires without detailed knowledge of the initial conditions.<ref name="Gray-2-224" /> Whenever spontaneous ignition is suspected, Gray recommends excavating the material, with photographs and temperature probe records at all stages. He has measured temperatures as high as 200 °C in buried material more than two weeks after a fire was put out. Unburnt oily rags at the bottom of a bin do not rule out spontaneous ignition either.<ref name="Gray-2-225" />

== Reconstructing the fire ==

A reconstruction places the evidence in the sequence of the fire. Van Rossum divides a room fire into three phases. In the development phase, a local fire of one or a few objects grows until flashover. After flashover the fire is fully developed, and the decay phase can begin, for example, when the fuel runs out or the fire brigade intervenes. These [[fire development stages]] matter for interpretation, because an active suppression system normally acts during the development phase and so prevents the fire from becoming fully developed.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>

[[Fire dynamics]], defined in a US nuclear regulatory report as the scientific study of hostile fires, describes ignition, flame spread, fire growth, smoke movement and their effects in an enclosure.<ref name="Iqbal-1-1">Iqbal and Salley (2004), p. 1-1.</ref> Smoke rises under buoyancy to the upper part of the room of origin and leaves through openings, driven mainly by pressure differences. The International Fire Engineering Guidelines (2005 edition) note that hand calculations of its spread beyond the room of origin are more difficult and more uncertain than those within it.<ref name="IFEG-2.5-2">National Research Council of Canada et al. (2005), p. 2.5-2.</ref><ref name="IFEG-2.5-6">National Research Council of Canada et al. (2005), p. 2.5-6.</ref>

Tests can fill gaps in the evidence. NIST set out to characterise the type, mass and layout of the combustibles in the towers, the fire endurance of the partitions and the properties of the insulation on the steel.<ref name="Gann-2">Gann, Hamins, et al. (2005), p. 2.</ref> Its reconstruction relied heavily on computer simulation, because the premises could not be examined after the fire and eyewitness information was severely limited. To support the simulations, NIST burned six single office workstations, the dominant combustibles in the buildings, to learn how they may have burned and to improve its fire model.<ref name="Ohlemiller-iii">Ohlemiller et al. (2005), p. iii.</ref>

== Modelling and computational fluid dynamics ==

[[Computational fluid dynamics]] (CFD) studies the flow of gases and liquids by solving the flow equations numerically on a grid of cells. A CFD model can show smoke spread, gas temperatures and velocities, flows through openings and the time to flashover in three dimensions as they change over time.<ref name="VR-11.1">Van Rossum (2027), §11.1.</ref><ref name="VR-11.2">Van Rossum (2027), §11.2.</ref> Turbulent flows, which are typical of fires, can only be approximated. CFD therefore gives good qualitative insight, but its exact results must be interpreted carefully and critically.<ref name="VR-11.1" /> Zone models such as CFAST, released by NIST,<ref name="VR-9.5">Van Rossum (2027), §9.5.</ref> are also used internationally for fire safety design and post-fire reconstruction.<ref name="Peacock-3">Peacock et al. (2026), p. 3.</ref>

In the World Trade Center investigation, the unusual mix of available information led to a high reliance on computational tools, and NIST upgraded its CFD model, the Fire Dynamics Simulator, for the reconstruction.<ref name="Gann-2" /><ref name="Gann-4">Gann, Hamins, et al. (2005), p. 4.</ref> It varied the uncertain inputs to find those to which the results were most sensitive and those that agreed best with the photographs.<ref name="Gann-2-3">Gann, Hamins, et al. (2005), pp. 2–3.</ref> The accuracy of the predictions was judged by their consistency with the photographic evidence.<ref name="Gann-4" /> For each tower it ran a less severe and a more severe case, which gave some understanding of the uncertainty in the predictions.<ref name="NIST-81">National Institute of Standards and Technology (2005), pp. 81–82.</ref>
[[File:fse-fire-investigation-v3.svg|thumb|upright=1.5|alt=Two candidate scenarios are tested against observations and model limitations before conclusions.|Alternative reconstructions should be tested against evidence and sensitivity. Based on Notarianni (2002), pp. 5-43–5-44 and McGrattan et al. (2026), p. 107.]]

Models also have limits. NIST decided not to model smoke movement and survival conditions throughout the occupied parts of the towers. There was no quantitative information on conditions inside the towers and no verifiable information on damage between floors, so such simulations for the impact floors and above would have been grossly uncertain.<ref name="Gann-3">Gann, Hamins, et al. (2005), p. 3.</ref>

The Fire Dynamics Simulator predicts the thermal environment of a fire, but it relies on empirical models for the activation of sprinklers and detectors.<ref name="FDS-107">McGrattan et al. (2026), p. 107.</ref> Smoke detector response is especially hard to model, because the production and transport of smoke early in a fire are not well understood.<ref name="FDS-108">McGrattan et al. (2026), p. 108.</ref> Notarianni adds that fire model outputs are single values that do not reflect the uncertainty in inputs such as fire growth rates. A predicted activation time of 121 s for a detector, for example, may in reality be longer or shorter, depending on uncertain inputs and on factors the model does not include.<ref name="Notarianni-5-43">Notarianni (2002), p. 5-43.</ref> In forensic reconstructions, the amount of soot deposited on surfaces in a simulation can be correlated with what is observed after the fire.<ref name="FDS-87">McGrattan et al. (2026), p. 87.</ref>

== Evaluating protection systems ==

An investigation compares what a system could do with what it actually did. NIST found that the sprinkler and standpipe systems of the towers had for the most part exceeded the code requirements of their time, but the adverse effects of the aircraft impacts on them were extensive.<ref name="Hopkins-xlv">Hopkins et al. (2005), p. xlv.</ref> WTC 1 was the first tower to be struck.<ref name="Hopkins-xxxi">Hopkins et al. (2005), p. xxxi.</ref> Its estimated impact damage would probably have destroyed at least one standpipe riser and the sprinkler systems on the 94th to 96th floors, and cut the water supply to other systems after a limited time.<ref name="Hopkins-xliii" /><ref name="Hopkins-xliv">Hopkins et al. (2005), p. xliv.</ref> The collapse of WTC 2 damaged the city water mains near the site, and the collapse of WTC 1 probably caused significant further damage.<ref name="Hopkins-xliv" />
[[File:fse-fire-investigation-v2.svg|thumb|upright=1.5|alt=Pre-incident conditions, ignition, detection, fire growth and consequences, with fire, water-supply and occupant tracks.|An investigation must align system states with the incident timeline. Based on Hopkins et al. (2005), pp. xliii–xlv and Van Rossum (2027), §4.11.]]

The evidence on systems is often incomplete. For the towers' suppression systems there was very little eyewitness or communications information. NIST therefore based its estimates on the incident information it had gathered, the likely effects of the impacts and historical performance records for sprinklers.<ref name="Hopkins-xxxi" /> Most of the New York fire department's reports of significant earlier fires documented the performance of detectors and sprinklers, but almost all lacked information on the smoke purge system.<ref name="Kuligowski-2" />

Which sprinklers opened, and when, also needs careful reading. Water droplets carried by the hot gas flow under the ceiling from the first sprinklers can cool the heat-sensitive links of sprinklers further away and delay their opening. Cooper calls this random effect sprinkler skipping, and fusible-link vents can be delayed in the same way.<ref name="Cooper-3-239">Cooper (2002b), p. 3-239.</ref> Evidence from victims has comparable limits. Carboxyhaemoglobin is routinely measured in the blood of fire victims, but blood cyanide often is not, and post-fire cyanide levels are hard to relate to the exposure during the fire.<ref name="Purser-2-100" /><ref name="Purser-2-103">Purser (2002), p. 2-103.</ref>

== Limits and use of findings ==

Investigators often work with fragmented information. NIST confirmed significant events from more than one source where possible, but this could not always be done, and it included events that it judged likely or probable from the accumulated information.<ref name="Hopkins-xxxi" /> Records can also be lost. The Port Authority of New York and New Jersey kept records of all significant fire events in the World Trade Center buildings, and these were lost in the collapse of the towers.<ref name="Kuligowski-1" /> Physical evidence may cover only a small and unrepresentative part of a building, as the recovered steel did.<ref name="Gayle-xli" />

A single investigation describes one event. Hall and Ahrens note that detailed accounts, including NFPA's reports of fire investigations, show the range and diversity of fires that can happen. Such anecdotes cannot be used to estimate incident rates or probabilities.<ref name="HA-5-70">Hall and Ahrens (2002), p. 5-70.</ref> Valid analysis of incident rates instead requires a statistically representative database of [[fire statistics]].<ref name="HA-5-69">Hall and Ahrens (2002), p. 5-69.</ref>

Collected investigation data can in turn feed design values. Holborn and colleagues analysed data from fire investigations in the Greater London area between 1996 and 2000 to derive fire sizes, fire growth rates and the times between events. The Australian data sheets for the Fire Safety Verification Method (print version 1.1, 2020) use their results for characteristic fire growth rates and for the share of fires that become fully developed.<ref name="Holborn-2004">Holborn et al. (2004), as cited in Australian Building Codes Board (2020a), Data Sheet B2, pp. 4–7.</ref> The World Trade Center investigation itself ended with 30 recommendations, covering structural integrity, fire endurance, active fire protection, evacuation, emergency response, procedures and practices, and education and training.<ref name="NIST-xiii">National Institute of Standards and Technology (2005), p. xiii.</ref>

== See also ==

* [[Firefighting]]
* [[Dry and wet risers]]
* [[Fire hydrant]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Averill, J. D., Mileti, D. S., Peacock, R. D., Kuligowski, E. D., Groner, N., Proulx, G., Reneke, P. A., & Nelson, H. E. (2005). ''Occupant behavior, egress, and emergency communications'' (NIST NCSTAR 1-7). National Institute of Standards and Technology.
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Gann, R. G., Hamins, A., McGrattan, K. B., Mulholland, G. W., Nelson, H. E., Ohlemiller, T. J., Pitts, W. M., & Prasad, K. R. (2005). ''Reconstruction of the fires in the World Trade Center towers'' (NIST NCSTAR 1-5). National Institute of Standards and Technology.
* Gayle, F. W., Fields, R. J., Luecke, W. E., Banovic, S. W., Foecke, T., McCowan, C. N., Siewert, T. A., & McColskey, J. D. (2005). ''Mechanical and metallurgical analysis of structural steel'' (NIST NCSTAR 1-3). National Institute of Standards and Technology.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-211–2-228). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Kuligowski, E. D., Evans, D. D., & Peacock, R. D. (2005). ''Post-construction fires prior to September 11, 2001'' (NIST NCSTAR 1-4A). National Institute of Standards and Technology.
* McGrattan, K., Hostikka, S., Floyd, J., McDermott, R., Vanella, M., Mueller, E., & Paul, C. (2026). ''Fire Dynamics Simulator technical reference guide: Vol. 1. Mathematical model'' (6th ed., NIST Special Publication 1018-1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.1018
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Ohlemiller, T. J., Mulholland, G. W., Maranghides, A., Filliben, J. J., & Gann, R. G. (2005). ''Fire tests of single office workstations'' (NIST NCSTAR 1-5C). National Institute of Standards and Technology.
* Peacock, R. D., McGrattan, K. B., Forney, G. P., & Reneke, P. A. (2026). ''CFAST – Consolidated Fire and Smoke Transport: Vol. 1. Technical reference guide'' (Version 7, NIST Technical Note 1889v1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.TN.1889v1
* Proulx, G. (2002). Movement of people: The evacuation timing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-342–3-366). National Fire Protection Association; Society of Fire Protection Engineers.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-83–2-171). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Firefighting

2026-11-02T18:37:06Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''Firefighting''' is the work of controlling and extinguishing fires, together with the rescue and protection tasks that go with it. A glossary published by the US Nuclear Regulatory Commission treats it as fire suppression, either manual, with hoses, portable extinguishers or manually operated fixed systems, or automatic, by systems using water, Halon or carbon dioxide.<ref name="NUREG-F29">Iqbal and Salley (2004), p. F-29.</ref> Besides attacking the fire, fire services search for and rescue occupants, protect property and limit harm to the environment.<ref name="IFEG-2.9-3">National Research Council of Canada et al. (2005), p. 2.9-3.</ref> Early action matters: an automatic extinguishing system generally intervenes while the fire is still in its growth stage, so the fire cannot become fully developed.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref> A fire service that arrives after flashover, by contrast, may have no effect on the fire itself.<ref name="IFEG-1.9-7">National Research Council of Canada et al. (2005), p. 1.9-7.</ref> Tactics differ between countries and situations; the Dutch fire service, for example, prefers to fight building fires from outside and attacks from inside only when an exterior attack fails and this can be done safely.<ref name="NIPV-43">Van der Graaf et al. (2021/2023), p. 43.</ref>

== Who fights fires and what they aim for ==

Many fires are fought first by the people who discover them. In the decision process that Bryan describes, an occupant who has recognised a fire chooses between flight, leaving the building, and fight, fetching an extinguisher or raising the alarm.<ref name="Bryan-3-318">Bryan (2002), p. 3-318.</ref> In a British study of 2,193 people at 952 fires, 14.9 % made fighting the fire their first action. In a US study of residential fires the share was 10.4 %, and in both studies men were more often active in fighting the fire.<ref name="Bryan-3-322">Bryan (2002), pp. 3-322–3-323.</ref> The Australian handbook to the Fire Safety Verification Method (print version 1.1, 2020) notes that many smouldering and small flaming fires are dealt with by occupants and never reported. Estimates of how often design fires occur are therefore commonly based on reported fires, ignoring suppression by occupants.<ref name="ABCBH-61">Australian Building Codes Board (2020b), pp. 61–62.</ref>

At industrial sites, trained staff and private fire brigades take part as well. The US glossary describes a fire watch: people trained to recognise fire hazards, to use fire extinguishers and to follow the proper notification procedures.<ref name="NUREG-F29" /> At US nuclear power plants, the fire brigade operates fixed systems by hand, removes fuel sources, switches off electrical systems and uses portable extinguishers and hose streams.<ref name="Nowlen-P5">Nowlen et al. (2005b), p. P-5.</ref> The International Fire Engineering Guidelines (2005 edition) include such private brigades, for example the brigade of an industrial complex, in their analysis of fire service intervention.<ref name="IFEG-1.9-1">National Research Council of Canada et al. (2005), p. 1.9-1.</ref>

The aims of firefighting go beyond putting out flames. According to the guidelines, fire services are commonly responsible for search and rescue, containing and extinguishing the fire and protecting property. They also protect the environment and the community, for example from contaminated firefighting water running off a chemical warehouse.<ref name="IFEG-2.9-3" /> Control means that the fire is kept from growing, for instance by wetting nearby combustibles and cooling the hot gases under the ceiling, while extinguishment is the complete suppression of all burning material.<ref name="NUREG-F25">Iqbal and Salley (2004), p. F-25.</ref> An attack can be offensive, applying water to the fire, or defensive, using hose streams to protect adjoining property, or both.<ref name="IFEG-1.9-4">National Research Council of Canada et al. (2005), p. 1.9-4.</ref>

== How fires are put out ==

[[Extinguishing mechanisms]] work by separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or the flame, or interfering with the chemistry of combustion. Several of them often act at once. Water on a burning solid cools the solid, so that it releases less flammable gas, and cools the flame, so that less heat reaches the fuel. Steam can keep oxygen away in some confined conditions, and a fog of fine droplets can block heat radiation.<ref name="NUREG-B15">Iqbal and Salley (2004), p. B-15.</ref> Water is the most common extinguishing agent because it is widely available, cheap and able to absorb a great deal of heat.<ref name="Fleming-4-72">Fleming (2002), p. 4-72.</ref> Fleming gives 9,280 Btu for one US gallon of water heated from 21 °C and turned into steam at 100 °C, which is about 2.6 MJ for every litre.<ref name="Fleming-4-72-SI">Fleming (2002), p. 4-72 (9,280 Btu per US gallon, converted to SI).</ref>
[[File:fse-firefighting-v1.svg|thumb|upright=1.5|alt=Control, extinction and exposure protection are supported by cooling, blanketing and chemical action.|Firefighting objectives and mechanisms must match the incident. Based on Iqbal and Salley (2004), p. B-15 and Fleming (2002), p. 4-72.]]

Water does not suit every fire. It is inappropriate for certain water-reactive materials, with which it can produce heat, flammable or toxic gases or explosions. Most hydrocarbon fuels are lighter than water and do not mix with it, so they float on the water and keep burning.<ref name="Fleming-4-72" /> On hot oil or fat, water can sink below the surface, turn to steam and throw out burning oil in a boilover.<ref name="NUREG-B58">Iqbal and Salley (2004), p. B-58.</ref> In the US classification of fires, water must never be used on Class D fires, which involve combustible metals such as magnesium, sodium and lithium.<ref name="NUREG-B16">Iqbal and Salley (2004), p. B-16.</ref>

Foam is the main alternative to water, used mostly on burning liquids.<ref name="NUREG-B58" /> Firefighting foam consists of air-filled bubbles made from water mixed with a foam concentrate, typically at 1, 3 or 6 percent. It floats on the fuel and forms a layer that keeps air out and stops the fuel from evaporating, so the fire goes out once the whole surface is covered. Low-expansion foam works well on a pool of liquid but much less well on running fuel or a pressurised spray, where an extra agent such as dry chemical is used.<ref name="Scheffey-4-88">Scheffey (2002), p. 4-88.</ref> Heat breaks foam down, so it must be applied fast enough and in large enough amounts to keep a layer over the fuel.<ref name="NUREG-B59">Iqbal and Salley (2004), p. B-59.</ref> A ruptured foam blanket can let the fire burn back and put firefighters at risk.<ref name="NUREG-B60">Iqbal and Salley (2004), p. B-60.</ref>

Dry chemical powders probably act mainly on the chemistry of the flame, and they also absorb heat, block radiation and, in one type, coat the burning surface. They leave residue that needs thorough cleaning and can corrode equipment.<ref name="NUREG-B55">Iqbal and Salley (2004), pp. B-55–B-56.</ref> In a 2001 fire at the Point Beach nuclear plant in the United States, the fire brigade discharged about 32 kg of dry chemical from three extinguishers without success. The fire was finally put out with 57 to 76 L of water, and white dust covered large parts of the containment building.<ref name="NUREG-H29">Iqbal and Salley (2004), p. H-29.</ref> Gaseous agents such as Halon 1301 put out visible flames almost at once, but glowing combustion inside a solid fuel can continue and re-ignite when air is let back in.<ref name="NUREG-B43">Iqbal and Salley (2004), pp. B-43–B-44.</ref>

== Manual firefighting: extinguishers, hoses and water ==

A [[Fire extinguisher]] is one of the means of manual suppression named in the US glossary, alongside hoses and manually operated fixed systems.<ref name="NUREG-F29" /> In the United States, its rating combines a number for relative effectiveness with a letter for each class of fire on which it has proved effective.<ref name="NUREG-F25" /> Class A covers ordinary combustibles such as wood and paper, B flammable liquids and gases, and C fires involving energised electrical equipment. Class D covers combustible metals and K cooking oils and fats.<ref name="NUREG-B16" /> Dry chemical agents are safe on electrical fires as far as electric shock is concerned, but they can damage delicate equipment.<ref name="NUREG-B55" />

Hose lines need a water supply that the fire service can reach. A [[Fire hydrant]] provides water to the pumpers of the fire department.<ref name="NUREG-F26">Iqbal and Salley (2004), p. F-26.</ref> In tall buildings, [[Dry and wet risers]] carry water to outlets on the floors, so firefighters can connect their hoses near the fire instead of laying them from the street.<ref name="NUREG-F61">Iqbal and Salley (2004), pp. F-61–F-62.</ref><ref name="Hopkins-21">Hopkins et al. (2005), p. 21.</ref> In New York City, supplying extra water to a building's fire protection systems is a routine fire department operation.<ref name="Hopkins-xlii">Hopkins et al. (2005), p. xlii.</ref> Reaching the hydrants, inlets and fire floor is a matter of [[fire service access]], which New Zealand's Verification Method C/VM2 (second edition, 2025) covers in its scenario for firefighting operations.<ref name="CVM2-53">Ministry of Business, Innovation and Employment (2025b), p. 53.</ref>

The water flow must match the size of the fire. The Netherlands Institute for Public Safety (NIPV) gives rules of thumb for cooling capacity. A high-pressure jet of 125 L/min is generally sufficient for a fire of up to about 2.5 MW, and a low-pressure jet of 450 L/min for up to about 10 MW.<ref name="NIPV-45">Van der Graaf et al. (2021/2023), p. 45.</ref> For comparison, Van Rossum gives about 2.5 MW for an average living-room sofa and a peak of 8.5 MW for a car.<ref name="VR-4.5">Van Rossum (2027), §4.5.</ref> He notes that such heat release data help the fire service judge whether a fire can still be fought with the flow its vehicle delivers at low, medium or high pressure.<ref name="VR-8.6">Van Rossum (2027), §8.6.</ref>

Time is often decisive. In an aircraft fuel spill fire, the aluminium skin of the aircraft can burn through in about 1 minute. The cabin becomes unsurvivable once the windows melt out after about 3 minutes.<ref name="Scheffey-4-103">Scheffey (2002), p. 4-103.</ref> Airport rescue and firefighting vehicles are designed to reach an incident on the airport within 2 to 3 minutes. Once there, they must apply agent to control the fire within 1 minute, a critical time recognised by US and international aviation and fire protection bodies.<ref name="Scheffey-4-103" />

== Automatic systems and the fire service ==

Automatic sprinklers often act long before firefighters can. Human response, from discovery of the fire to the travel of the fire brigade, usually takes much longer than the time sprinklers need to control a fire in its early stages. Sprinklers are designed to control a fire, but they often put it out, because the wetted materials around it can no longer heat up to their ignition temperature.<ref name="NUREG-10-1">Iqbal and Salley (2004), pp. 10-1–10-2.</ref> Even where sprinklers do not suppress a fire, their cooling can protect the structure until the fire is extinguished by other means.<ref name="Fleming-4-72" />

Manual and automatic firefighting both depend on the water supply. Sprinkler systems fail when a supply valve is closed, a water tank is empty, a fire pump does not start or loses its power, or the pipes and heads are blocked or corroded.<ref name="NUREG-10-2">Iqbal and Salley (2004), p. 10-2.</ref> At World Trade Center 7, the sprinklers on the lower 20 floors depended on one automatic fire pump and on the city main.<ref name="Hopkins-xli">Hopkins et al. (2005), p. xli.</ref> After the collapse of WTC 1, the fire department could not provide firefighting or supplementary water to the building.<ref name="Hopkins-xliv">Hopkins et al. (2005), p. xliv.</ref> In the SFPE Handbook, Siu warns that many fire risk studies for nuclear power plants ignore the reliance of automatic and manual suppression on a common water supply, which can make their results non-conservative.<ref name="Siu-5-221">Siu (2002), p. 5-221.</ref>
[[File:fse-firefighting-v2.svg|thumb|upright=1.5|alt=Extinguisher, hydrant and hose line, and automatic sprinkler have different operating chains.|Manual and automatic suppression have different dependencies. Based on Iqbal and Salley (2004), pp. F-25–F-26 and 10-1–10-2.]]

Risk studies of US nuclear power plants estimate from past events how long manual firefighting takes. For all fire types together, NUREG/CR-6850 (2005) gives a probability of 0.46 that a fire is still burning after 10 minutes of manual suppression, and 0.10 after 30 minutes.<ref name="Nowlen-P9">Nowlen et al. (2005b), pp. P-9–P-10.</ref> These curves leave out the time to detect the fire and the response time of the fire brigade. Both must be subtracted from the time before damage occurs to find the time that is actually available for suppression.<ref name="Nowlen-P9" />

== Tactics: inside or outside, offensive or defensive ==

Firefighting tactics weigh the chance of success against the risk to firefighters. The International Fire Engineering Guidelines note that a shortage of water or of firefighters for an interior attack can change the strategy from offensive, fighting the fire, to defensive. The defensive aim is to stop the fire spreading to adjoining buildings.<ref name="IFEG-2.9-4">National Research Council of Canada et al. (2005), p. 2.9-4.</ref>

The Dutch fire service arranges its tactics in a quadrant model. The goal is either to prevent fire growth or to extinguish the seat of the fire, and the attack is made either from inside or from outside the building. Firefighters prefer to fight a fire from outside, and they carry out an interior attack only in a small room or building when an exterior attack fails and it can be done safely. A smoke-filled space is entered only if the benefits outweigh the risks, and reducing material damage is not a reason to take risks.<ref name="NIPV-43" />

The Dutch basic principles start with taking time to stop and think, followed by a reconnaissance from outside, for example with a thermal imaging camera. Three questions then decide the type of attack: is it known where the fire is, can it be reached from outside, and is there enough cooling capacity.<ref name="NIPV-44">Van der Graaf et al. (2021/2023), p. 44.</ref> If the fire cannot be found, reached and cooled from outside, large buildings are fought defensively and considered beyond saving.<ref name="NIPV-44" /> In a small building an offensive interior attack may still be possible, with control of the doors, the building kept closed where possible and water on the fire as quickly as possible.<ref name="NIPV-63">Van der Graaf et al. (2021/2023), p. 63.</ref>

An interior attack also needs a short route through smoke and enough cooling capacity, and the commanding officer on site makes the final decision.<ref name="NIPV-45" /> Van Rossum stresses the same point for engineering studies: a positive result does not mean that the fire service will attack from inside, because that decision always rests with the fire service on site.<ref name="VR-9.3">Van Rossum (2027), §9.3 (Results from zone models).</ref> The Australian handbook, summarising limits from the Fire Brigade Intervention Model, adds that search and rescue cannot be carried out in a room that has reached flashover.<ref name="ABCBH-113">Australian Building Codes Board (2020b), p. 113.</ref>

== Ventilation, backdraft and smoke explosions ==

Firefighters also change the ventilation of a burning building. [[Positive pressure ventilation]] uses fans to blow fresh air into an enclosure, creating a pressure difference that drives the existing air and combustion products out through an exit opening. It is used to influence the degree of ventilation, to assist firefighting and to influence the burning itself.<ref name="NUREG-F46">Iqbal and Salley (2004), p. F-46.</ref>
[[File:fse-firefighting-v3.svg|thumb|upright=1.5|alt=Fan airflow changes smoke flow and can supply oxygen to hot unburned gases.|Ventilation can alter both visibility and combustion conditions. Based on Iqbal and Salley (2004), p. F-46 and Van Rossum (2027), §4.9.]]

Adding air is risky when a fire is short of oxygen. In a ventilation-controlled fire the oxygen supply limits the burning, so unburnt pyrolysis gases can build up, and mixed with oxygen they form a flammable mixture that needs only ignition energy.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref> A [[Backdraft]] is the explosive ignition of such gases when fresh air suddenly enters, for example when a door is opened, and it can produce a large fireball or a jet of flame. Van Rossum describes it as a dangerous phenomenon for the fire service.<ref name="VR-4.9">Van Rossum (2027), §4.9.</ref>

A [[smoke explosion]] is a different event. It is the very rapid burning of flammable gases that are already reasonably premixed with air within their explosion limits, set off by a spark, by glowing particles or by self-ignition.<ref name="VR-4.10">Van Rossum (2027), §4.10.</ref> The Dutch basic principles favour keeping a building closed where possible, which they call anti-ventilation, and controlling the doors during an interior attack.<ref name="NIPV-63" />

Ventilation, smoke control and sprinklers also affect one another. The NIPV study notes that smoke and heat removal can raise the chance of a successful interior attack in indoor car parks.<ref name="NIPV-6">Van der Graaf et al. (2021/2023), p. 6.</ref> Building ventilation systems that keep running during a fire, or that recirculate air, can themselves spread smoke through the building.<ref name="Evans-70">Evans et al. (2005), p. 70.</ref> Sprinkler sprays can also cool the heat-sensitive links of downstream sprinklers and smoke vents and delay their opening, effects known as sprinkler skipping and vent skipping.<ref name="Cooper-3-239">Cooper (2002b), p. 3-239.</ref>

== Firefighting in building design and regulation ==

The International Fire Engineering Guidelines state that evacuation analysis should not rely on fire service intervention, although the needs of fire services must not be discounted.<ref name="IFEG-1.9-1" /> In New Zealand, C/VM2 (second edition, 2025) sets out a design scenario for firefighting operations. It sets requirements for access, water supply, information for firefighters and structural stability.<ref name="CVM2-53" /> For large unsprinklered firecells near a boundary, it sets limits for the moment when firefighters first apply water. The radiation at 1.5 m above the floor may then not exceed 4.5 kW/m², and the smoke layer must be at least 2 m above the floor.<ref name="CVM2-53" /> That moment may be taken as 1,200 s, or 1,000 s with a fire alarm connected directly to a remote receiving centre.<ref name="CVM2-54">Ministry of Business, Innovation and Employment (2025b), p. 54.</ref>

In Australia, the Fire Safety Verification Method Standard 2022 includes a fire brigade intervention scenario, assessed with the Fire Brigade Intervention Model, that applies to buildings within 50 km road travel of a fire station.<ref name="FSVM-15">Australian Building Codes Board (2022), p. 15.</ref> The 2020 handbook shows how a design fire may be cut short by occupants, by sprinklers, or by fire brigade suppression before or after flashover.<ref name="ABCBH-61" /> The design fire is then modified for the automatic or fire brigade intervention that applies to the scenario.<ref name="ABCBH-61" />

In the Netherlands, an equivalent solution under the 2012 Building Decree cannot take credit for a fire service attack.<ref name="NIPV-15">Van der Graaf et al. (2021/2023), p. 15.</ref> The NIPV study stresses that the fire service has an obligation of best efforts rather than of result.<ref name="NIPV-41">Van der Graaf et al. (2021/2023), p. 41.</ref> Some Dutch design curves do include firefighting: the car fire curve in the car park standard NEN 6098, as described by Van Rossum, reflects the extinguishing action of the fire service.<ref name="VR-8.6" />

== Limits and common misconceptions ==

Putting out the visible flames does not always end a fire. Glowing combustion inside solids can survive a gaseous agent and re-ignite when air returns, and a damaged foam blanket can let a liquid fire burn back.<ref name="NUREG-B43" /><ref name="NUREG-B60" /> Battery packs of electric vehicles can catch fire again shortly after the flames are out. They therefore need continuous cooling and temperature monitoring, for example in a water-filled immersion container.<ref name="NIPV-46">Van der Graaf et al. (2021/2023), p. 46.</ref>

More agent is not automatically better. Water can spread a burning liquid that floats on it, and repeated discharges of dry chemical at Point Beach left residue across the containment building without putting the fire out.<ref name="Fleming-4-72" /><ref name="NUREG-H29" /> In enclosed spaces, dry chemical can also impair breathing and reduce visibility.<ref name="NUREG-H29" /> Firefighting itself exposes firefighters to heat, flame, smoke, explosion and structural collapse, as one of the US definitions of fire suppression states.<ref name="NUREG-F29" />

Engineering models cannot promise what firefighters will find. The International Fire Engineering Guidelines note that the effect of fire service activities does not lend itself easily to quantification, so many aspects rest on qualitative judgement.<ref name="IFEG-2.9-2">National Research Council of Canada et al. (2005), p. 2.9-2.</ref> C/VM2's limits apply only at the moment firefighters first apply water, and operations after that depend on the conditions they face at the time.<ref name="CVM2-54" />

== See also ==

* [[Hose reel]]
* [[Rollover]]
* [[Electric vehicle fire]]
* [[Critical water application rate]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-88–4-122). National Fire Protection Association; Society of Fire Protection Engineers.
* Siu, N. (2002). Fire risk assessment for nuclear power plants. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-214–5-226). National Fire Protection Association; Society of Fire Protection Engineers.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Fire service access

2026-11-02T18:37:00Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''Fire service access''' is the set of provisions that let the fire service reach a building, deliver water to every part of it, and carry out [[firefighting]] and rescue inside with reasonable safety.<ref name="CVM2-53">Ministry of Business, Innovation and Employment (2025b), p. 53.</ref><ref name="IFEG-1.2-10">National Research Council of Canada et al. (2005), p. 1.2-10.</ref> In New Zealand, the Building Code clauses restated in Verification Method C/VM2 (second edition, 2025) cover a hard-standing for fire vehicles, water throughout the building, routes to the fire floor and information for firefighters.<ref name="CVM2-53" /> The International Fire Engineering Guidelines (2005 edition) treat access to the site and to the building as part of fire services intervention, one of the six sub-systems of a fire safety design.<ref name="IFEG-1.2-10" /> Access matters because the time needed to bring water to a fire affects how far the fire develops and whether it can still be suppressed.<ref name="NIPV-66">Van der Graaf et al. (2021/2023), p. 66.</ref> A fire service that arrives after the fire has grown beyond flashover may have no effect on it at all.<ref name="IFEG-1.9-7">National Research Council of Canada et al. (2005), p. 1.9-7.</ref> Requirements differ between countries; in the Netherlands, for example, the Building Works and Living Environment Decree (Bbl) counts the preservation of fire service attack routes among its sub-goals.<ref name="VR-1.2">Van Rossum (2027), §1.2.</ref>

== What fire service access includes ==

New Zealand's Building Code clause C5 deals with access and safety for firefighting operations. Its functional requirements, as printed in the 2013 commentary, ask for a low probability that firefighters are delayed or impeded, and a low probability that they are injured or made ill.<ref name="Comm-32">Ministry of Business, Innovation and Employment (2013), p. 32.</ref> Verification Method C/VM2 (second edition, 2025) restates the performance clauses. Fire service vehicles need a hard-standing from which an unobstructed path leads to the building within 20 m of the firefighter entrance and of any sprinkler or hydrant inlets. Firefighters, with their protective equipment and standard training, must be able to reach the floor of fire origin, search the area around it and protect their way out.<ref name="CVM2-53" /> Clear information about the fire and the building is also required, and the structure that carries the access routes must stay stable during and after the fire.<ref name="CVM2-53" />
[[File:fse-fire-service-access-v1.svg|thumb|upright=1.5|alt=Arrival leads through hard-standing, connections and internal routes to firefighting and egress.|Fire service access connects vehicles, equipment, personnel and safe withdrawal. Based on Ministry of Business, Innovation and Employment (2025b), pp. 53–55.]]

In Australia, the handbook to the Fire Safety Verification Method (print version 1.1, 2020) lists facilities for firefighting among the broad fire safety objectives of the National Construction Code.<ref name="ABCBH-27">Australian Building Codes Board (2020b), p. 27.</ref> It calls for a firefighter strategy, a plan by which the fire brigade is notified of the fire and its location and gains access to the site. The brigade also receives the correct fire location and communication facilities on arrival, documents on the fire safety strategy, and a set-up area with facilities for firefighting and for search and rescue. The plan has to be developed with the fire authority, using the Fire Brigade Intervention Model where appropriate.<ref name="ABCBH-29">Australian Building Codes Board (2020b), p. 29.</ref>

The International Fire Engineering Guidelines cover public fire services as well as private ones, such as the fire brigade of an industrial complex.<ref name="IFEG-1.9-1">National Research Council of Canada et al. (2005), p. 1.9-1.</ref> For this sub-system they list measures such as the type of fire service, full-time or volunteer, its capability and resources, access to the site and the building, and water supplies.<ref name="IFEG-1.2-10" /> In the Netherlands, the Bbl keeps the attack routes of the fire service intact as one of its sub-goals.<ref name="VR-1.2" /> Under the Bbl, a non-enclosed space through which an escape route runs must also remove enough heat and smoke, and admit enough fresh air, to stay usable for escape, rescue and firefighting work.<ref name="VR-7.7">Van Rossum (2027), §7.7.</ref>

== How access affects the time to intervention ==

The International Fire Engineering Guidelines describe intervention as a sequence of steps, each of which takes time. The fire service has to be notified, dispatched and driven to the site, and a station with full-time paid firefighters is likely to respond faster than one run by volunteers.<ref name="IFEG-1.9-2">National Research Council of Canada et al. (2005), p. 1.9-2.</ref> On arrival, crews locate the fire from installed equipment, from occupants and from the sight of smoke and flames. They then move vehicles, hoses and other equipment into position, a step that fire conditions in or near the building may affect. Search and rescue and the attack follow, and the attack can be offensive, putting water on the fire, or defensive, protecting adjoining property with hose streams, or both.<ref name="IFEG-1.9-4">National Research Council of Canada et al. (2005), p. 1.9-4.</ref>

Access shapes several of these steps. The location of a building and the access to it affect the travel time, while its size, layout and signage affect investigation, search, rescue and firefighting. The location of hydrants, fire indicator panels and other fire service facilities affects how efficiently the fire is suppressed.<ref name="IFEG-1.9-5">National Research Council of Canada et al. (2005), p. 1.9-5.</ref> The guidelines also warn that this sub-system changes over the life of a building, as fire station locations, budgets, equipment and traffic density change.<ref name="IFEG-1.9-2" />

The arrival time largely decides what an attack can achieve, and the guidelines distinguish three outcomes: no effect, control and extinguishment. No effect fits a fire service that arrives after the fire has grown beyond flashover. Control, in which the fire burns at a steady size until the fuel is used up, is a conservative assumption often made when access to the fire is limited.<ref name="IFEG-1.9-7" /> A risk model in the SFPE Handbook likewise judges the effectiveness of firefighting from the time of flashover and the arrival time of the fire brigade.<ref name="Meacham-5-164">Meacham (2002), p. 5-164.</ref> Studies of fires in health care buildings, quoted by Bryan, single out the period between detection and the arrival of the fire department. They see it as the most important life-saving period for the area in direct contact with the room of origin.<ref name="Bryan-3-315">Lerup et al. (1978), as cited in Bryan (2002), p. 3-315.</ref>

In Australia the main tool for estimating these times is the Fire Brigade Intervention Model (FBIM) of the Australasian Fire Authorities Council (AFAC).<ref name="IFEG-2.9-2">National Research Council of Canada et al. (2005), p. 2.9-2.</ref> It is built from up to 16 flow charts for steps such as notification, dispatch, travel, putting on safety equipment and setting up the water supply.<ref name="IFEG-2.9-3">National Research Council of Canada et al. (2005), pp. 2.9-3–2.9-5.</ref> It can estimate, for example, how long firefighters need to reach a given location in a building.<ref name="IFEG-2.9-4">National Research Council of Canada et al. (2005), p. 2.9-4.</ref> Its numerical values were prepared solely from Australian data, but because no other country has compiled such a guide, they may have at least a semi-quantitative use elsewhere.<ref name="IFEG-3.9-2">National Research Council of Canada et al. (2005), p. 3.9-2.</ref>

== Vehicle access and hard-standing ==

New Zealand's C/VM2 (second edition, 2025) repeats clause C5.3: a hard-standing from which an unobstructed path leads to the building within 20 m of the firefighter entrance and any sprinkler or hydrant inlets. Under clause C5.4, firecells larger than 5,000 m² without sprinklers need such access on more than one side.<ref name="CVM2-53" /> The 2013 commentary adds that these access points should be spread around the building, not placed on both sides of one corner served by the same hard-standing. It also notes that the clauses use conventional methods that the Fire Service can easily anticipate, so unusual solutions should be agreed with it in advance.<ref name="Comm-33">Ministry of Business, Innovation and Employment (2013), p. 33.</ref> According to the commentary, clauses C5.3 to C5.8 do not apply to detached dwellings, the inside of household units in multi-unit dwellings, backcountry huts, outbuildings or ancillary buildings.<ref name="Comm-32" />

In Australia, the Fire Safety Verification Method Standard 2022 requires external fire brigade access and external hydrants for every building assessed under its fire brigade intervention scenario.<ref name="FSVM-16">Australian Building Codes Board (2022), p. 16.</ref> That scenario applies only to buildings within 50 km road travel of a fire station.<ref name="FSVM-15">Australian Building Codes Board (2022), p. 15.</ref> For buildings further away, the 2020 handbook states that fire brigade intervention should not be taken into account, and that the design brief should address its absence and any need for compensating measures.<ref name="ABCBH-86">Australian Building Codes Board (2020b), p. 86.</ref>

Indoor car parks show how access can limit firefighting in practice. A study by the Netherlands Institute for Public Safety (NIPV) names heat, loss of visibility, long hose distances and the difficulty of finding one's bearings. Together they make reconnaissance and firefighting in such car parks difficult and risky.<ref name="NIPV-11">Van der Graaf et al. (2021/2023), p. 11.</ref> It recommends placing charging spaces for electric vehicles near the vehicle entrances and exits and at street level where possible. This aids accessibility and raises the chance that a fire can be fought from outside or the vehicle removed more quickly.<ref name="NIPV-42">Van der Graaf et al. (2021/2023), p. 42.</ref> Higher decks are not always easy to reach, and a fire service entrance that is also an escape route creates conflicting safety interests.<ref name="NIPV-39">Van der Graaf et al. (2021/2023), p. 39.</ref>

== Water for firefighting: hydrants, inlets and risers ==

A [[Fire hydrant]] is a device that supplies water to fire department pumpers for fighting fires in buildings.<ref name="NUREG-F26">Iqbal and Salley (2004), p. F-26.</ref> A fire department connection is an inlet through which the fire service pumps water from its vehicles into the fire protection system of a building.<ref name="NUREG-F25">Iqbal and Salley (2004), p. F-25.</ref> Inside, a standpipe or riser system of pipes, valves and hose connections carries the water to the floors. Trained occupants can use its hoses until the fire department arrives, and firefighters can connect their own hoses to outlets near the fire.<ref name="NUREG-F61">Iqbal and Salley (2004), pp. F-61–F-62.</ref> [[Dry and wet risers]] differ in how they are filled. A wet system is always full of water and connected to an automatic supply, whereas a manual dry system has only fire department connections and relies on the fire service for water.<ref name="Hopkins-21">Hopkins et al. (2005), p. 21.</ref><ref name="NUREG-F61" />
[[File:fse-fire-service-access-v2.svg|thumb|upright=1.5|alt=Hydrant feeds a pumper, while an inlet feeds a riser and hose outlets inside a building.|Hydrants, inlets and internal risers have distinct functions. Based on Iqbal and Salley (2004), pp. F-25–F-26 and F-61–F-62, and Hopkins et al. (2005), pp. xxxiv–xxxv.]]

New Zealand and Australian rules also limit how far water may have to be carried. Under C/VM2, a pumping appliance parked close to the building must be able to reach any point inside within 75 m, about three hose lengths. Otherwise an internal hydrant is needed, designed to NZS 4510 or approved by the National Commander of Fire and Emergency New Zealand.<ref name="CVM2-54">Ministry of Business, Innovation and Employment (2025b), pp. 54–55.</ref> C/VM2 treats access to an intermediate floor as achieved when a hydrant in a safe path lies within 40 m of its most remote point, about two hose lengths.<ref name="CVM2-55">Ministry of Business, Innovation and Employment (2025b), p. 55.</ref> Australia's 2022 standard requires internal hydrants in a sprinklered building when reaching all points needs more than 100 m or the building has more than three levels. Without sprinklers the distance threshold is 70 m.<ref name="FSVM-16" />

Risers shorten the hose that firefighters must lay. The NIPV study notes that a dry riser can shorten the attack time because less hose has to be rolled out. Its most effective location is where the fire service enters the car park.<ref name="NIPV-66" /> A NIST report on the World Trade Center states that avoiding long hose lays from the fire engine to an upper floor of a tall building improves the initial attack. It adds that standpipes are not an alternative to automatic sprinklers.<ref name="Hopkins-21" />

An accessible inlet does not guarantee water. Sprinkler and pump systems can fail because of a closed supply valve, an empty tank, a fire pump that does not start or loses its power, or an inadequate supply.<ref name="NUREG-10-2">Iqbal and Salley (2004), p. 10-2.</ref> At World Trade Center 7, the sprinklers on floors 1 to 20 depended on one automatic fire pump and on the city main near the building.<ref name="Hopkins-xli">Hopkins et al. (2005), p. xli.</ref> After the collapse of WTC 1, the fire department could not provide firefighting or supplementary water to WTC 7.<ref name="Hopkins-xliv">Hopkins et al. (2005), p. xliv.</ref> C/VM2 asks that access and firefighter safety be designed with regard to the likelihood and consequences of failure of any fire safety system.<ref name="CVM2-53" />

== Reaching the fire floor: stairs, lifts and high-rise buildings ==

C/VM2 links the protection of the internal route to the height of the building. Where the escape height exceeds 10 m, floors that cannot be reached directly from street level must be served by fire-separated stairways that resist fire spread until burnout. In lower buildings these stairways must last 60 minutes from ignition or until burnout.<ref name="CVM2-55" /> Pressurised stairwells keep smoke out by holding the stair at a higher air pressure than the fire floor. Their main aim is a smoke-free escape route, and a secondary aim is a smoke-free staging area for firefighters.<ref name="Klote-4-286">Klote (2002), p. 4-286.</ref>

In a [[high-rise building]] the climb itself becomes a barrier. NIST's study of the emergency response at the World Trade Center notes that a New York firefighter in full protective clothing and breathing apparatus carries about 23 kg. Extra equipment can add another 23 kg or more.<ref name="Lawson-xliii">Lawson and Vettori (2005), p. xliii.</ref> Fully equipped firefighters climbed WTC 1 at about 2.0 minutes per floor, and their fitness for rescue and firefighting fell with every floor climbed.<ref name="Lawson-xliii" /><ref name="Lawson-xliv">Lawson and Vettori (2005), p. xliv.</ref> Another NIST report gives a typical pace of about one minute per floor, which is hard to sustain beyond about the first 20 storeys. Even at that pace, reaching the 60th floor would take about an hour.<ref name="Lew-191">Lew et al. (2005), p. 191.</ref>

A [[firefighting lift]] removes most of that climb. When a fire is detected, lifts are normally taken out of service and recalled to the ground floor. Fire services carry keys that let them run the lifts for rescue and to carry crews and equipment towards the fire.<ref name="Klote-4-289">Klote (2002), p. 4-289.</ref> In 2005, NIST found that US building codes, with a few exceptions, did not permit fire-protected lifts for routine access by first responders. The United Kingdom and other countries using British standards had required such firefighter lifts in protected shafts for a number of years.<ref name="Lew-191" /> NIST's final report recommended fire-protected and structurally hardened lifts in tall buildings, reserved for emergency responders during emergencies.<ref name="NIST-218">National Institute of Standards and Technology (2005), p. 218.</ref>

Each World Trade Center tower had four vertical water supply zones, with standpipes in the stairwells feeding hose stations on every floor. Manual fire pumps on the 7th, 41st and 75th floors boosted the pressure, and fourteen ground-level fire department connections served the complex.<ref name="Hopkins-xxxiv">Hopkins et al. (2005), pp. xxxiv–xxxv.</ref> New York City's 2003 building code requires emergency power in new high-rise office buildings for fire pumps, at least three lifts, alarms, emergency lighting and smoke control.<ref name="Razza-4">Razza and Grill (2005c), p. 4.</ref>

== Conditions firefighters can work in ==

Access is only useful if conditions at the end of the route allow work. New Zealand's clause C3.8 covers unsprinklered firecells within 15 m of a relevant boundary with a fire load above 20 TJ or a floor area above 5,000 m². When firefighters first apply water to such a fire, the radiation at 1.5 m above the floor may not exceed 4.5 kW/m², and the smoke layer must be at least 2 m above the floor.<ref name="CVM2-53" /> C/VM2 lets designers take the time until water is first applied as 1,200 s (20 minutes), or 1,000 s with an automatic alarm connected directly to a remote receiving centre. Another time may be used if a fire brigade intervention model supports it.<ref name="CVM2-54" /> The 2013 commentary on the first edition explains that the same values are rounded 95th percentiles from New Zealand industrial fires, about 1,240 s with a monitored alarm and 1,060 s with a direct connection.<ref name="Comm-149">Ministry of Business, Innovation and Employment (2013), p. 149.</ref>

Australia's 2020 handbook summarises firefighter limits from the FBIM manual, measured 1.5 m above the floor and to be confirmed with the fire brigade. In routine conditions firefighters may work for up to 25 minutes at up to 100 °C and 1 kW/m². In hazardous conditions the limits are 10 minutes, 120 °C and 3 kW/m².<ref name="ABCBH-112">Australian Building Codes Board (2020b), p. 112.</ref> Extreme conditions, such as a snatch rescue or a retreat from flashover, allow 1 minute at 160 °C and 4 to 4.5 kW/m². Above 235 °C or 10 kW/m² conditions are life-threatening, and no search and rescue is possible in a room after flashover.<ref name="ABCBH-112" /><ref name="ABCBH-113">Australian Building Codes Board (2020b), p. 113.</ref> Poor visibility is not a limit in itself, but it slows search and firefighting, and the air supply of the breathing apparatus may run out first.<ref name="ABCBH-111">Australian Building Codes Board (2020b), p. 111.</ref>

In the Netherlands, the standard NEN 6093 on smoke and heat exhaust systems sets limits for a fire service attack in a space with such a system. Visibility must be at least 100 m to light-emitting objects up to 1.8 m above the floor, and radiation from the smoke layer at most 3.5 kW/m² at that height. The smoke layer may reach 200 °C where goods are stored in it and 500 °C otherwise, and it must stay below the critical temperature of the structure.<ref name="VR-9.3">Van Rossum (2027), §9.3 (Results from zone models).</ref> Van Rossum adds that firefighters need to know whether the fire is still local or already a compartment fire, and whether they can attack with the fire in sight.<ref name="VR-9.3" />

The structure must also hold long enough. C/VM2 requires the structure that gives firefighters access to floors to remain stable during and after the fire, with its fire resistance derived from a full burnout design fire.<ref name="CVM2-53" /><ref name="CVM2-54" /> Australia's 2022 standard pairs its fire brigade intervention scenario with a scenario that guards against unexpected catastrophic structural failure.<ref name="FSVM-16" />

== Information, communication and upkeep ==

Firefighters arriving at a building need to know where the fire is and what they can use. New Zealand's clause C5.7 asks for clear information on the general location of the fire, the available fire safety systems and any hazardous substances or processes.<ref name="CVM2-53" /> Australia's 2022 standard asks for command and control provisions in unsprinklered buildings and in sprinklered buildings of more than three levels.<ref name="FSVM-16" /> New York City's 2003 code requires two-way voice communication and a fire command station in new office buildings over 75 ft (about 23 m).<ref name="Razza-4" />
[[File:fse-fire-service-access-v3.svg|thumb|upright=1.5|alt=Fire location, system status and hazardous materials inform access and suppression choices.|Responders need current information as well as physical access. Based on Ministry of Business, Innovation and Employment (2025b), p. 53.]]

Access provisions have to stay usable for the whole life of the building. The International Fire Engineering Guidelines list the items whose design and maintenance support intervention: perimeter roads, the access paths and lifts used by the fire service, and equipment such as hydrants. The list also includes protective measures such as structural stability, sprinklers, smoke management and emergency communication.<ref name="IFEG-1.9-8">National Research Council of Canada et al. (2005), p. 1.9-8.</ref> The New Zealand version of the guidelines adds that alterations or a change of use can compromise the original fire engineering design and may call for a new evaluation.<ref name="IFEG-0.3-8-NZ">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.3-8.</ref>

== Limits and common misconceptions ==

Fire service access does not make the fire service part of the evacuation design. The International Fire Engineering Guidelines state that evacuation analysis should not rely on fire service intervention, although the needs of fire services must not be discounted.<ref name="IFEG-1.9-1" /> In the Netherlands, an equivalent solution under the 2012 Building Decree cannot take credit for a fire service attack.<ref name="NIPV-15">Van der Graaf et al. (2021/2023), p. 15.</ref> The fire service has an obligation of best efforts rather than of result, so its deployment cannot replace fire prevention measures.<ref name="NIPV-41">Van der Graaf et al. (2021/2023), p. 41.</ref>

A positive engineering result does not oblige firefighters to attack from inside the building. Van Rossum stresses that this decision always rests with the fire service on site.<ref name="VR-9.3" /> Likewise, the C/VM2 limits describe a single moment, and later operations are decided by the officer in charge according to the conditions found.<ref name="Comm-149" />

Fire service intervention is also hard to quantify. The International Fire Engineering Guidelines note that its effect does not lend itself easily to calculation, so many aspects rest on qualitative judgement.<ref name="IFEG-2.9-2" /> The FBIM values come from Australian data only.<ref name="IFEG-3.9-2" />

== See also ==

* [[Hose reel]]
* [[Positive pressure ventilation]]
* [[Fire extinguisher]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Klote, J. H. (2002). Smoke control. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-274–4-291). National Fire Protection Association; Society of Fire Protection Engineers.
* Lawson, J. R., & Vettori, R. L. (2005). ''The emergency response operations'' (NIST NCSTAR 1-8). National Institute of Standards and Technology.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* Ministry of Business, Innovation and Employment. (2013). ''Commentary for Building Code clauses C1–C6 and Verification Method C/VM2''.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Razza, J. C., & Grill, R. A. (2005c). ''Comparison of the 1968 and current (2003) New York City Building Code provisions'' (NIST NCSTAR 1-1F). National Institute of Standards and Technology.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Hose reel

2026-11-02T18:36:38Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

A '''hose reel''' is a fire hose kept permanently connected to the water supply of a building, so that trained occupants or employees can fight a fire before the fire department arrives.<ref name="IS-F62">Iqbal and Salley (2004), p. F-62.</ref><ref name="IS-F61">Iqbal and Salley (2004), p. F-61.</ref> The glossary of NUREG-1805 defines a related term, the small hose system, as hose of 5/8 in. to 1½ in. (about 16 to 38 mm) diameter for the use of employees, intended to control and extinguish fires in their earliest stage.<ref name="IS-F50">Iqbal and Salley (2004), p. F-50.</ref> The International Fire Engineering Guidelines name hose reels, together with fire extinguishers, as the means by which building occupants may suppress a fire.<ref name="IFEG-1.7-1">National Research Council of Canada et al. (2005), pp. 1.7-1–1.7-2.</ref> In high-rise buildings, such hoses may hang on the standpipes, which also provide connections for the hoses that firefighters carry in.<ref name="Evans-9">Evans et al. (2005), p. 9.</ref>

Rules for hose reels differ between countries and documents. In the United States, NFPA 14 (2000 edition), as summarised by NIST, provides Class II hose stations with 38 mm (1½ in.) hose for trained occupants, designed for about 380 L/min (100 gal/min).<ref name="Hopkins-20">Hopkins et al. (2005), p. 20.</ref> The 1968 New York City Building Code required occupant hose reels and, for that reason, had no requirements for fire extinguishers.<ref name="Lew-151">Lew et al. (2005), p. 151.</ref> Their value depends on the user: fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they belong to a trained emergency crew.<ref name="IFEG-1.7-7">National Research Council of Canada et al. (2005), p. 1.7-7.</ref> Water also does not suit every fire, and NUREG-1805 warns never to use it on burning metals.<ref name="IS-B16">Iqbal and Salley (2004), p. B-16.</ref>

== Definition and terminology ==

The glossary of NUREG-1805, a report of the US Nuclear Regulatory Commission, uses several related terms. A small hose system is hose of 5/8 in. to 1½ in. diameter for the use of employees, intended to control and extinguish incipient fires.<ref name="IS-F50" /> An incipient fire is one that can still be controlled with portable extinguishers, Class II standpipes or small hose systems, without protective clothing or breathing apparatus.<ref name="IS-F38">Iqbal and Salley (2004), p. F-38.</ref> A standpipe hose cabinet holds standpipe outlets or stored fire hose, and the hoses are usually pre-connected and kept in a rack with release pins.<ref name="IS-F61" /> The list of abbreviations in the same report uses FHR for fire hose reel.<ref name="IS-G4">Iqbal and Salley (2004), p. G-4.</ref>

Many high-rise and other large buildings have an internal system of water mains, the standpipes, connected to fire hose stations; these pipes are covered under [[Dry and wet risers]].<ref name="IS-F62" /> In the World Trade Center (WTC) towers in New York, hoses pre-connected to the standpipes in the stairwells were installed for trained occupants. The same standpipes offered hose connections for the fire department on every floor.<ref name="Evans-xxix">Evans et al. (2005), p. xxix.</ref> For WTC 7, the NIST investigation describes hose reels in the stair enclosures and hose cabinets throughout the floors.<ref name="Hopkins-128">Hopkins et al. (2005), p. 128.</ref> A hose reel is not the same as a fire hydrant, which supplies water to fire department pumpers.<ref name="IS-F26">Iqbal and Salley (2004), p. F-26.</ref> Nor is it a fire department connection, through which the fire department pumps water from its trucks into a building system.<ref name="IS-F25">Iqbal and Salley (2004), p. F-25.</ref>

== Components and layout ==

In the WTC towers, a typical hose rack started with a 64 mm (2½ in.) standpipe valve and a reducer to 38 mm (1½ in.). A rack or cabinet then held 38 m (125 ft) of fire hose with a nozzle.<ref name="Hopkins-40">Hopkins et al. (2005), p. 40.</ref> The racks were mounted about 1.4 m (4½ ft) above the stair landing. This arrangement let the fire department or a fire brigade start manual firefighting with the smaller hose without carrying hoses up from the ground floor.<ref name="Hopkins-40" /> Such a station was provided on every floor of every stair. Extra hose cabinets were added so that the whole building lay within 7.6 m (25 ft) of the end of a hose nozzle.<ref name="Hopkins-127">Hopkins et al. (2005), p. 127.</ref>
[[File:fse-hose-reel-v1.svg|thumb|upright=1.5|alt=Water supply passes through a valve and hose to a nozzle aimed at the fire.|A hose reel works as a connected assembly, not as an isolated fitting. Based on Iqbal and Salley (2004), pp. F-61–F-62.]]

The 1968 Building Code of the City of New York was used for the design of WTC 1 and 2. It required standpipes to be placed so that a 6.1 m (20 ft) stream from a nozzle on at most 38 m (125 ft) of hose could reach every point of every floor.<ref name="GJ-29">Grill and Johnson (2005b), p. 29.</ref> Hose stations had to stand at the standpipe risers, inside or next to the entrances of the stair enclosures.<ref name="GJ-30">Grill and Johnson (2005b), p. 30.</ref> In the occupancy groups that included the business use of the towers, the hose was 1½ in. unlined linen hose, and auxiliary hose stations with the same hose were allowed.<ref name="GJ-2">Grill and Johnson (2005b), p. 2.</ref><ref name="GJ-30" /> Water had to be available at every hose outlet at all times, or be made available automatically when a hose valve was opened.<ref name="GJ-30" />

NFPA 14 (2000 edition), as summarised by NIST, spaces Class II hose stations so that every area lies within 6.1 m (20 ft) of the nozzle of a 30 m (100 ft) hose.<ref name="Hopkins-20" /> These stations provide small streams for trained occupants or fire brigades to fight incipient fires and to finish off afterwards. Class I systems instead have 64 mm valves that supply heavy streams for the fire department in advanced fires, and Class III systems combine both.<ref name="Hopkins-20" />

== Water supply, flow and pressure ==

A hose reel is only as good as its [[fire water supply]]. Wet standpipes, the preferred arrangement, are filled with water at all times and connected to an automatic supply such as the city mains, a tank with a pump, or an elevated tank.<ref name="Hopkins-21">Hopkins et al. (2005), p. 21.</ref> Manual dry standpipes have only fire department connections and no automatic supply.<ref name="Hopkins-21" /> In NUREG-1805, a manual standpipe relies on the fire service to supply it, and a semi-automatic standpipe needs a control device to be activated before water reaches the hose outlets.<ref name="IS-F61" />

The flows are modest compared with those for the fire service. NFPA 14 (2000 edition), as summarised by NIST, designs Class II systems for about 380 L/min (100 gal/min) at about 450 kPa (65 psi) at the most demanding standpipe.<ref name="Hopkins-20" /> Class I and III systems are designed for about 1,900 L/min (500 gal/min) at about 690 kPa (100 psi).<ref name="Hopkins-20" /> The Building Code of the City of New York (1968) specified that pressure-reducing valves at 1½ in. hose stations should limit the pressure to about 590 kPa (85 psi) at 265 L/min (70 gal/min).<ref name="Hopkins-148">Hopkins et al. (2005), p. 148.</ref> In the WTC towers, tanks of about 19 m³ (5,000 gal) could supply about 1,900 L/min (500 gal/min) for 10 minutes, so that manual firefighting could begin before the manual fire pumps were started.<ref name="Hopkins-39">Hopkins et al. (2005), p. 39.</ref>

Hose reels can share their supply with other systems. In WTC 7, the hose connections were supplied from combined sprinkler and standpipe systems, so they had the same supply zones as the sprinklers.<ref name="Hopkins-149">Hopkins et al. (2005), p. 149.</ref> For the lowest 20 floors, a loss of power to the automatic fire pump or significant damage to the city main could interrupt that supply.<ref name="Hopkins-xli">Hopkins et al. (2005), p. xli.</ref> According to NUREG/CR-6850, a rupture of the firefighting water main in a US nuclear power plant could make all water-based suppression, including manual hose stations, unavailable until the break is isolated.<ref name="Nowlen-13-3">Nowlen et al. (2005b), p. 13-3.</ref> Several outlets on one supply also compete for water. In NIST's calculations, four hose valves at the top of a WTC tower needed three or four fire pumps, while two pumps could supply only one.<ref name="Hopkins-148" />
[[File:fse-hose-reel-v2.svg|thumb|upright=1.5|alt=One riser and pump supply several hose reels, with an independent backup path.|Shared infrastructure can disable multiple hose outlets at once. Based on Hopkins et al. (2005), pp. xli and 149 and Nowlen et al. (2005b), p. 13-3.]]

== How water puts out a fire ==

A fire needs fuel, oxygen and enough heat, the three sides of the fire triangle described in ''Introduction to Fire Safety Engineering''.<ref name="VR-4.2">Van Rossum (2027), §4.2.</ref> Water from a hose acts on this triangle in several ways at once. When it reaches a burning solid, it cools the fuel, which then releases less flammable gas. It also cools the flames, so that they feed less heat back to the fuel.<ref name="IS-B15">Iqbal and Salley (2004), p. B-15.</ref> The steam it forms may keep oxygen away from the fire in some confined conditions, and a water fog may block heat radiation.<ref name="IS-B15" />

Water is the most commonly used extinguishing agent, mainly because it is widely available and cheap, and because it has a high specific heat and a high latent heat of evaporation.<ref name="Fleming-72">Fleming (2002), p. 4-72.</ref> The specific heat of water, 4,186 J/(kg·K), is about four times that of air, and turning water into steam takes extra energy on top of that.<ref name="VR-3.4">Van Rossum (2027), §3.4.</ref> Fleming gives 9,280 Btu for one US gallon of water heated from a room temperature of 21 °C until it has turned into steam at 100 °C. That is about 2.6 MJ per litre.<ref name="Fleming-72" />

A fire at the Point Beach nuclear plant in the United States in 2001 shows how little water a small fire can need. The fire brigade first discharged about 32 kg (70 lb) of dry chemical from three portable extinguishers without putting the fire out.<ref name="IS-H29">Iqbal and Salley (2004), p. H-29.</ref> It then extinguished the fire easily with a hose line, using 57 to 76 L (15 to 20 gal) of water.<ref name="IS-H29" /><ref name="IS-H30">Iqbal and Salley (2004), p. H-30.</ref> The dry chemical had covered large areas with white dust, whereas the small quantity of water left little to clean up.<ref name="IS-H29" /><ref name="IS-H30" />

== Fires for which water is unsuitable ==

Water does not suit every fire. In the table of fire classes in NUREG-1805, water is listed for Class A fires in ordinary combustibles such as wood, cloth, paper, rubber and many plastics.<ref name="IS-B16" /> It is not listed for flammable liquids and gases, for energised electrical equipment or for cooking oils and fats. Water and water-based extinguishers should never be used on Class D fires in combustible metals such as magnesium, sodium or lithium.<ref name="IS-B16" />

Liquids need special care. A burning liquid that is lighter than water and does not mix with it simply floats on the water and keeps burning.<ref name="IS-B58">Iqbal and Salley (2004), p. B-58.</ref> Water applied to a burning oil or fat far above the boiling point of water turns to steam below the surface. The steam can throw out the oil in an eruption that spreads the fire.<ref name="IS-B58" /> Some materials react with water and can produce heat, flammable or toxic gases or explosions, although enough water can overcome small amounts of such materials.<ref name="Fleming-72" />
[[File:fse-hose-reel-v3.svg|thumb|upright=1.5|alt=Trained responder deploys hose past obstructions and checks water-compatible fuel and egress.|Hose deployment requires access, training and a suitable fire scenario. Based on Evans et al. (2005), p. 9 and Iqbal and Salley (2004), pp. B-16 and B-58.]]

== Who uses a hose reel ==

Hose reels are meant for [[firefighting]] by trained occupants and staff in the first stage of a fire, although firefighters can use them too. In NUREG-1805, trained occupants or employees operate the hoses until the fire department arrives, after which firefighters can connect their own hoses to outlets near the fire.<ref name="IS-F62" /> NIST notes that the safe and effective use of pre-connected hoses requires training.<ref name="Evans-9" /> In the WTC towers, each hose station was intended for a trained fire brigade or the New York City fire department.<ref name="Hopkins-xxxiv">Hopkins et al. (2005), p. xxxiv.</ref> At the Waterford 3 nuclear plant in 1985, the fire brigade used a local hose station and water streams to put out a feedwater pump fire in about 10 minutes.<ref name="IS-H13">Iqbal and Salley (2004), p. H-13.</ref>

How far a design may rely on occupants is uncertain. NIST describes a long-standing debate about relying on occupants to use pre-connected hoses, and notes that some jurisdictions allow only Class I standpipes, for fire department use.<ref name="Hopkins-21" /> The International Fire Engineering Guidelines state that fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they belong to a specially trained site emergency crew.<ref name="IFEG-1.7-7" /> If there is good reason to expect effective firefighting by occupants, the analysis may include it, together with the time at which it starts.<ref name="IFEG-1.7-7" /> Its effect on the design fire is then taken as no effect, control or extinguishment.<ref name="IFEG-1.7-4">National Research Council of Canada et al. (2005), p. 1.7-4.</ref>

Research on human behaviour helps to explain this caution. In the SFPE Handbook, Bryan describes how a person who has recognised a fire decides between leaving the building and fighting the fire, for example with an extinguisher.<ref name="Bryan-318">Bryan (2002), p. 3-318.</ref> People in a familiar role and familiar surroundings, such as those with firefighting training, are likely to choose more suitable actions.<ref name="Bryan-319">Bryan (2002), p. 3-319.</ref> In a study of an office building fire in Osaka, the regular occupants fought the fire and alerted others, while people attending training sessions there, who did not know the building, mainly evacuated.<ref name="Horiuchi">Horiuchi et al. (1986), as cited in Bryan (2002), pp. 3-319 and 3-340.</ref>

== Hose reels, extinguishers and sprinklers ==

The International Fire Engineering Guidelines treat hose reels and [[fire extinguisher]]s alike, as means of suppression by occupants within the detection, warning and suppression sub-system.<ref name="IFEG-1.7-1" /><ref name="IFEG-1.2-10">National Research Council of Canada et al. (2005), p. 1.2-10.</ref> Building codes do not always require both. NIST found that the 1968 New York City Building Code had no requirements for fire extinguishers, because it required occupant hose reels instead.<ref name="Lew-151" /> The Port Authority's design guidelines for the WTC nevertheless required portable extinguishers in all spaces, under a fire department directive and the New York City Fire Prevention Code.<ref name="GJc-17">Grill and Johnson (2005c), p. 17.</ref> For battery rooms in US nuclear power plants, NRC Regulatory Guide 1.189, as summarised in NUREG-1805, says that a hose station and portable extinguishers should be readily available outside the room.<ref name="IS-16-6">Iqbal and Salley (2004), p. 16-6.</ref>

Hose reels are not a substitute for automatic sprinklers, and NIST notes that standpipe systems are not considered an alternative to automatic fire suppression.<ref name="Hopkins-21" /> NUREG-1805 explains that sprinklers typically use less water than fire hoses. The human response, from discovering the fire to the arrival of a fire brigade, usually takes much longer than sprinklers need to control a fire in its early stage.<ref name="IS-10-1">Iqbal and Salley (2004), p. 10-1.</ref> Even in a sprinklered building, people with extinguishers or hose lines are generally needed to put out all the burning, especially where the fire is shielded from the sprinkler spray.<ref name="Evans-9" />

In Australian performance-based design, firefighting by occupants is usually left out of the design fire. The handbook for the Fire Safety Verification Method notes that many smouldering and small flaming fires are dealt with by the occupants and therefore go unreported.<ref name="ABCB-61">Australian Building Codes Board (2020b), pp. 61–62.</ref> It is common practice to consider reported fires only and to ignore suppression by occupants.<ref name="ABCB-61" /> For the risk of a major structural collapse, the handbook suggests deriving the frequency of fires that occupants could not manage from fire statistics.<ref name="ABCB-92">Australian Building Codes Board (2020b), p. 92.</ref>

== Reliability and maintenance ==

A hose reel can fail anywhere between the water source and the nozzle. For sprinkler systems, NUREG-1805 lists causes of water supply failure such as a closed water supply valve, a broken supply header, an empty water tank and a fire pump that does not start.<ref name="IS-10-2">Iqbal and Salley (2004), p. 10-2.</ref> Where hose stations share that supply, as they did in WTC 7, the same faults would affect them.<ref name="Hopkins-149" /> For US nuclear power plants, NUREG/CR-6850 asks whether hose stations would survive an earthquake, whether an alternative source of firefighting water exists and whether there is enough hose to use it.<ref name="Nowlen-13-7">Nowlen et al. (2005b), pp. 13-7–13-8.</ref> Where a water hose reel is credited, the analyst also checks that vulnerable components are shielded from water spray and that drainage is adequate. Floor penetrations must be verified as sealed, so that firefighting water cannot run into the compartment below.<ref name="Nowlen-11-18">Nowlen et al. (2005b), p. 11-18.</ref>

Performance records are not kept for standpipe and pre-connected hose systems, and NIST found their performance difficult to assess.<ref name="Hopkins-21" /><ref name="Hopkins-xlii">Hopkins et al. (2005), p. xlii.</ref> At the WTC, these systems met the 1968 New York City Building Code but not the flow rates and durations of NFPA 14 (2000 edition), against which NIST checked them.<ref name="Evans-xxxi">Evans et al. (2005), p. xxxi.</ref><ref name="Hopkins-148" /> The International Fire Engineering Guidelines ask that active fire protection equipment be maintained in line with the relevant codes, standards and manufacturer's literature, in some jurisdictions through essential safety provisions.<ref name="IFEG-1.7-8">National Research Council of Canada et al. (2005), p. 1.7-8.</ref> Among the American standards, NUREG-1805 lists NFPA 1962 (2003 edition) on the inspection, care and use of fire hose, couplings and nozzles and the service testing of fire hose.<ref name="IS-E12">Iqbal and Salley (2004), p. E-12.</ref>

== See also ==

* [[Fire hydrant]]
* [[Fire classes]]
* [[Fire service access]]
* [[Firefighting lift]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Grill, R. A., & Johnson, D. A. (2005b). ''Fire protection and life safety provisions applied to the design and construction of WTC 1, 2, and 7 and post-construction provisions applied after occupancy'' (NIST NCSTAR 1-1D). National Institute of Standards and Technology.
* Grill, R. A., & Johnson, D. A. (2005c). ''Post-construction modifications to fire protection and life safety systems of the World Trade Center towers'' (NIST NCSTAR 1-1H). National Institute of Standards and Technology.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Fire hydrant

2026-11-02T18:36:31Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

A '''fire hydrant''' is a device that provides a water supply to fire department pumpers for use in fighting structure fires.<ref name="IS-F26">Iqbal and Salley (2004), p. F-26.</ref> Fire engines connect to it and pump the water onwards, through hose lines to the fire or into the fire department connections of a building.<ref name="Evans-18">Evans et al. (2005), p. 18.</ref><ref name="LV-229">Lawson and Vettori (2005), p. 229.</ref> Those connections let the fire department pump water into the fire protection systems of the building, such as its sprinklers and standpipes.<ref name="IS-F25">Iqbal and Salley (2004), p. F-25.</ref><ref name="Evans-9">Evans et al. (2005), p. 9.</ref> In the defence-in-depth approach used for US nuclear power plants, fire hydrants, hose stations and water supply systems are among the measures that limit fire spread.<ref name="IS-1-2">Iqbal and Salley (2004), p. 1-2.</ref>

The water a hydrant can deliver depends on the mains behind it, and hydrants serve as the measuring points when the flow and pressure of a supply are tested.<ref name="Fleming-81">Fleming (2002), p. 4-81.</ref> Rules for hydrants differ between countries. In New Zealand, Verification Method C/VM2 (second edition, 2025) accepts, for example, a pumping appliance parked so that every point of a building can be reached within 75 m, about three hose lengths.<ref name="MBIE-54">Ministry of Business, Innovation and Employment (2025b), p. 54.</ref> In Australia, the fire brigade intervention scenario of the Fire Safety Verification Method Standard 2022 requires external hydrants for every building and internal hydrants in larger or taller ones.<ref name="ABCB22">Australian Building Codes Board (2022), pp. 15–16.</ref> A hydrant is only as reliable as its supply: after the World Trade Center (WTC) towers in New York collapsed in 2001, there was no usable water in lower Manhattan's hydrant system.<ref name="McA-304">McAllister et al. (2008), p. 304.</ref>

== Definition and types ==

The glossary of NUREG-1805, a report of the US Nuclear Regulatory Commission, defines a hydrant by its purpose: it supplies water to fire department pumpers.<ref name="IS-F26" /> A fire department connection works the other way round. It is a device through which the fire department pumps water from its trucks into a fire protection system.<ref name="IS-F25" /> A standpipe system is the piping, risers, valves and hose connections that supply fire hoses inside a building for occupants or firefighters.<ref name="IS-F62">Iqbal and Salley (2004), p. F-62.</ref> A hydrant selected to measure the water flow available from a supply is called a flow hydrant.<ref name="IS-F32">Iqbal and Salley (2004), p. F-32.</ref> Its list of abbreviations also names double-outlet and quadruple-outlet fire hydrants and wall hydrants.<ref name="IS-G">Iqbal and Salley (2004), pp. G-3, G-9 and G-11.</ref>

The word covers more than the street hydrant on a public main. The NIST investigation of the WTC cites the American standard NFPA 14 as the ''Standard for the Installation of Standpipe, Private Hydrant, and Hose Systems''.<ref name="Hopkins-xxxii">Hopkins et al. (2005), p. xxxii.</ref> The SFPE Handbook names NFPA 24 as the standard for the installation of private fire service mains and their appurtenances.<ref name="Fleming-73">Fleming (2002), p. 4-73.</ref> In New Zealand, C/VM2 refers to an internal hydrant installed to NZS 4510, ''Fire hydrant systems for buildings'', and lists its 2008 edition with Amendment 1.<ref name="MBIE-54" /><ref name="MBIE-60">Ministry of Business, Innovation and Employment (2025b), p. 60.</ref> Inside tall buildings, standpipes supply the hose connections on each floor, a subject covered under [[Dry and wet risers]].<ref name="Evans-9" /> In WTC 7, one standpipe in a stairway supplied hose valves on the 45th to 47th floors and also a manifold roof hydrant.<ref name="Evans-28">Evans et al. (2005), p. 28.</ref>

In the International Fire Engineering Guidelines (2005 edition), the hydrant layout is an input to the analysis of fire service intervention, agreed in the fire engineering brief.<ref name="IFEG-1.9-3">National Research Council of Canada et al. (2005), p. 1.9-3.</ref> The guidelines state that the location of hydrants and other fire service facilities affects the efficiency of fire suppression.<ref name="IFEG-1.9-5">National Research Council of Canada et al. (2005), p. 1.9-5.</ref> They also count the amount of available firefighting water among the factors that govern the capability of a fire service.<ref name="IFEG-1.9-5" /> Before the attack can begin, vehicles, hoses and other equipment may first need to be moved into position.<ref name="IFEG-1.9-4">National Research Council of Canada et al. (2005), p. 1.9-4.</ref>

== From hydrant to nozzle ==

In [[firefighting]], a hydrant does not put out a fire on its own. An engine connected to it pumps the water onwards, either through hose lines or into the fire department connections of a building.<ref name="Evans-18" /> In the second case, the standpipes and sprinklers of the building carry the water further.<ref name="Evans-9" /> The NIST timeline of the 2001 WTC response records engines that hooked up to hydrants that still worked and relayed the water to other engines.<ref name="LV-229" /> One engine took water from a hydrant on West Street, laid an 89 mm (3½ in.) supply line to a tower ladder and also supplied the standpipe of a neighbouring building.<ref name="LV-229" />
[[File:fse-fire-hydrant-v1.svg|thumb|upright=1.5|alt=Source, hydrant, pumper, hoses and nozzle form a chain to the fire.|A hydrant supplies a pumping appliance rather than extinguishing directly. Based on Iqbal and Salley (2004), p. F-26 and Evans et al. (2005), p. 18.]]

The New York City fire department (FDNY) used two kinds of pumper at fires in high-rise buildings. Conventional pumpers had two-stage pumps of 4 or 8 m³/min (1,000 or 2,000 gal/min).<ref name="McA-77">McAllister et al. (2008), p. 77.</ref> High-pressure pumpers had a third stage that could supply 2 m³/min (500 gal/min) at 4.8 MPa (700 psi).<ref name="McA-77" /> The FDNY high-rise manual advised feeding a standpipe system with at least two pumpers at two different fire department connections.<ref name="McA-77" /> Its recommended pump pressures allowed for the nozzle pressure, the height of the floor and the friction losses in the building's pipes and in the hose lines.<ref name="McA-77" />

The flow a fire needs can be far more than one hose line delivers. Using standard fire service methods, the NIST report on the emergency response estimated that about 4,700 L/min (1,250 gal/min) would be needed to extinguish a fire on half a floor of a WTC tower.<ref name="LV-41">Lawson and Vettori (2005), p. 41.</ref> That half floor measured about 1,350 m², and the flow corresponds to roughly five hand lines of 63.5 mm diameter.<ref name="LV-41" /> A full floor would have needed about 9,400 L/min and some ten hose lines, an operation for at least 15 to 20 engine companies.<ref name="LV-77">Lawson and Vettori (2005), p. 77.</ref>

For car fires, the Netherlands Institute for Public Safety (NIPV) gives much smaller rules of thumb. A high-pressure jet of 125 L/min is generally sufficient up to a heat release rate of 2.5 MW, and a low-pressure jet of 450 L/min up to 10 MW.<ref name="NIPV-45">Van der Graaf et al. (2021/2023), p. 45.</ref> ''Introduction to Fire Safety Engineering'' explains that fire engines can work at low, medium or high pressure, each with a different volume flow.<ref name="VR-8.6">Van Rossum (2027), §8.6.</ref> Knowing the heat release rate of a burning object helps crews judge whether a fire can still be fought with a given flow.<ref name="VR-8.6" />

== Flow, pressure and testing ==

The flow a hydrant can give depends on the pressure in the main and on the outlet. In the SFPE Handbook chapter on hydraulics, Titus explains that water discharging into the open air from a tank, hydrant or nozzle is affected by the area and shape of the opening.<ref name="Titus-62">Titus (2002), p. 4-62.</ref> The flow from a hydrant outlet is normally found from the outlet diameter, the pressure measured with a pitot gauge in the stream and a coefficient for the outlet shape.<ref name="Titus-65">Titus (2002), p. 4-65.</ref> For full flow across a standard 63.5 mm (2½ in.) outlet, that coefficient is usually taken as 0.90.<ref name="Titus-65" /> Without a pitot gauge, the flow can be estimated from the outlet height and the distance the stream travels, a method Titus calls relatively inaccurate but useful as a bounding guide.<ref name="Titus-65" />

Hydrants are also the usual measuring points when a public or private water supply is tested. In the method that Fleming describes in the SFPE Handbook, the static pressure is read from a gauge on one hydrant.<ref name="Fleming-81" /> The residual pressure is read from the same gauge while water flows from another hydrant, preferably downstream.<ref name="Fleming-81" /> The static pressure mainly reflects elevated tanks and running pumps, while the drop to the residual pressure reflects friction and other losses in the pipes.<ref name="Fleming-81" /> The resulting water supply curve is therefore a fingerprint of the supply and its piping.<ref name="Fleming-81" /> NUREG-1805 lists NFPA 291, ''Recommended Practice for Fire Flow Testing and Marking of Hydrants'' (2002 edition), among the American standards.<ref name="IS-E6">Iqbal and Salley (2004), p. E-6.</ref>

Because a public supply is rarely without any flow, the static reading represents the network carrying only its ordinary demand.<ref name="Fleming-81" /> Fleming gives a worked example. A supply tested at a static pressure of 6.9 bar (100 psi) fell to a residual pressure of 5.5 bar (80 psi) while 3,785 L/min (1,000 gpm) flowed.<ref name="Fleming-81" /> Read from the plotted supply curve, the same supply would still give about 6.2 bar (90 psi) at 1,703 L/min (450 gpm).<ref name="Fleming-81" /> In the American sprinkler design practice that Fleming describes, the demand of the system, including an allowance for hose streams, should lie below this curve.<ref name="Fleming-81" />

Real networks differ widely. Around the WTC, the city supply was a gridded network of ductile iron mains of about 510 and 300 mm (20 in. and 12 in.) diameter.<ref name="Hopkins-xxxiii">Hopkins et al. (2005), p. xxxiii.</ref> Water could flow along many paths through this grid, which kept friction losses small while large volumes were flowing.<ref name="Hopkins-xxxiii" /> The standard flows of about 1,900 L/min (500 gal/min) in the smaller mains and about 2,800 L/min (750 gal/min) in the larger ones typically caused no recognisable pressure drop.<ref name="Hopkins-xxxiv">Hopkins et al. (2005), p. xxxiv.</ref> The average static pressure of the grid was about 340 kPa (50 psi).<ref name="Hopkins-xxxix">Hopkins et al. (2005), p. xxxix.</ref>

== Location and access rules ==

Where hydrants and fire engines must be placed is set by national rules, and these rules differ. In New Zealand, Verification Method C/VM2 (second edition, 2025) sets out the Building Code clauses for firefighting operations.<ref name="MBIE-53">Ministry of Business, Innovation and Employment (2025b), p. 53.</ref> Clause C5.3 requires [[fire service access]] for vehicles to a hard-standing with an unobstructed path to the building within 20 m of the firefighter entrance and of any sprinkler or hydrant inlets.<ref name="MBIE-53" /> Clause C5.5 requires the means to deliver water for firefighting to all parts of the building.<ref name="MBIE-53" />

C/VM2 accepts two ways to meet clause C5.5. The first is a pumping appliance parked so close that any point in the building lies within 75 m, about three hose lengths.<ref name="MBIE-54" /> The second is an internal hydrant installed to NZS 4510 or approved by the National Commander of Fire and Emergency New Zealand.<ref name="MBIE-54" /> For intermediate floors, a comment accepts a hydrant in a safe path no more than 40 m from the most remote point. This corresponds to about two hose lengths, with some allowance for an indirect route.<ref name="MBIE-55">Ministry of Business, Innovation and Employment (2025b), p. 55.</ref>

The 2013 commentary on the first edition of C/VM2 explains the purpose of these clauses. For the officer in charge to judge an attack safely, information must be available on arrival and a protected route must lead to the upper floors.<ref name="MBIE13-151">Ministry of Business, Innovation and Employment (2013), p. 151.</ref> Firefighting water must also be available near the fire.<ref name="MBIE13-151" /> In the commentary's example of a sprinklered hotel, a pumping appliance parked within 5.0 m of the building takes water from street hydrants. Every point of the ground floor then lies within three hose lengths (75 m), while building fire hydrant systems in the stairways serve the upper floors.<ref name="MBIE13-196">Ministry of Business, Innovation and Employment (2013), p. 196.</ref>
[[File:fse-fire-hydrant-v3.svg|thumb|upright=1.5|alt=Pumper at hard-standing connects to hydrant and hoses reach fire through protected access.|Firefighting access includes vehicles, connections, internal routes and safe egress. Based on Ministry of Business, Innovation and Employment (2025b), pp. 53–55.]]

The second edition also sets conditions for the moment firefighters first apply water in some unsprinklered firecells. These are firecells within 15 m of a relevant boundary with a fire load above 20 TJ or a floor area above 5,000 m².<ref name="MBIE-53" /> At that moment, the radiation at 1.5 m above the floor may not exceed 4.5 kW/m², and the smoke layer must be at least 2 m above the floor.<ref name="MBIE-53" /> The moment may be taken as 1,200 s after ignition, or 1,000 s where automatic detection is directly connected to a remote receiving centre.<ref name="MBIE-54" />

In Australia, the Fire Safety Verification Method Standard 2022 includes a fire brigade intervention scenario for buildings within 50 km road travel of a fire station. Compliance is shown with the Fire Brigade Intervention Model of the Australasian Fire and Emergency Service Authorities Council (AFAC).<ref name="ABCB22" /> Table 2.8 of the standard requires external fire hydrants for every building. Internal hydrants are required in buildings of more than three levels. They are also required where the distance to all points exceeds 100 m in a sprinklered building, or 70 m in one without sprinklers.<ref name="ABCB22" />

Where the water is not enough, tactics change. A fire service with too little water or too few firefighters may switch from fighting the fire to stopping its spread to adjoining buildings, according to the International Fire Engineering Guidelines.<ref name="IFEG-2.9-4">National Research Council of Canada et al. (2005), p. 2.9-4.</ref> For indoor car parks in the Netherlands, NIPV notes that the time needed to bring water to the fire affects how the fire develops.<ref name="NIPV-66">Van der Graaf et al. (2021/2023), p. 66.</ref> A dry riser can shorten the attack, because less hose has to be rolled out. NIPV therefore advises placing it where the fire service enters the car park.<ref name="NIPV-66" />

== Water supply behind the hydrant ==

Every hydrant depends on the [[fire water supply]] behind it: the mains and, in larger systems, tanks, pumps and connections. The NIST investigation describes such a system at the WTC in detail. The complex took its water from the city distribution system through a fire main that looped the site.<ref name="Hopkins-xxxv">Hopkins et al. (2005), p. xxxv.</ref> This main was fed by two redundant connections of about 410 mm (16 in.), and electric fire pumps maintained its operating pressure.<ref name="Hopkins-xxxv" /> Emergency generators provided back-up power, and tanks of about 19 m³ (5,000 gal) in the towers held the first water for the fire brigade or the fire department.<ref name="Hopkins-xxxv" /> Without refilling, these tanks gave the maintenance staff about 10 minutes to start the manual fire pumps.<ref name="Hopkins-xxxv" />

Redundancy only helps when the supply routes are independent. The towers had two connections, at Vesey Street and Liberty Street, with isolation valves so that either main could operate on its own.<ref name="Hopkins-xxxix" /> Fourteen fire department connection stations at street level let the fire department add water and pressure.<ref name="Hopkins-xxxv" /> WTC 7, by contrast, was fed by two connections only about 3.7 m (12 ft) apart from the same city main.<ref name="Hopkins-xxxix" /><ref name="Hopkins-xl">Hopkins et al. (2005), p. xl.</ref> A loss of power to its automatic fire pump or significant damage to that main could interrupt the supply to the sprinklers on floors 1 to 20.<ref name="Hopkins-xli">Hopkins et al. (2005), p. xli.</ref> In New York, the fire department routinely provided a supplemental supply, which was considered infinite in duration.<ref name="Hopkins-xlii">Hopkins et al. (2005), p. xlii.</ref>
[[File:fse-fire-hydrant-v2.svg|thumb|upright=1.5|alt=Municipal main, reserve tank, fire pump and fire department connection feed one distribution system, with shared failure points.|Redundant supplies require independent availability when needed. Based on Hopkins et al. (2005), pp. xxxiv–xxxv and pp. xxxix–xli.]]

== When the supply fails ==

Many causes of a failed supply lie away from the hydrant itself. For sprinkler systems, NUREG-1805 lists a closed water supply valve, a broken supply header and an empty water tank.<ref name="IS-10-2">Iqbal and Salley (2004), p. 10-2.</ref> An electric fire pump may fail to start after a power failure, and a diesel pump through poor maintenance, dead batteries or a lack of fuel.<ref name="IS-10-2" /> For US nuclear power plants, NUREG/CR-6850 asks whether an earthquake could disable fire pumps, water piping, standpipes and tanks at the same time.<ref name="Nowlen-13-7">Nowlen et al. (2005b), p. 13-7.</ref> It reports concern about cast-iron fire mains, because cast iron is seismically weak.<ref name="Nowlen-13-2">Nowlen et al. (2005b), p. 13-2.</ref> It also asks whether an alternative source of firefighting water, and enough hose to use it, is available.<ref name="Nowlen-13-8">Nowlen et al. (2005b), p. 13-8.</ref>

The attacks of 11 September 2001 showed how a hydrant network can fail in a large incident. The collapse of the two towers damaged the city water system in the surrounding streets.<ref name="Hopkins-xxxi">Hopkins et al. (2005), p. xxxi.</ref> Around 11:30 a.m., there was no water in the hydrant system or in the standpipes of WTC 7.<ref name="McA-78">McAllister et al. (2008), p. 78.</ref> An FDNY engine at the corner of WTC 7 was still connected to a hydrant with its pump running, although the engine itself was on fire.<ref name="LV-110">Lawson and Vettori (2005), p. 110.</ref> Fire boats on the Hudson River began stretching lines towards the site, and engines elsewhere relayed water from hydrants that still worked.<ref name="LV-110" /><ref name="LV-229" />

Rescue work, care for the injured and the loss of hydrant water meant that the fire department could not consider fighting the WTC 7 fires until about 1:00 p.m.<ref name="McA-627">McAllister et al. (2008), p. 627.</ref> At about 2:30 p.m. it ordered its personnel to withdraw from the building. The reasons included growing fires, possible structural damage, the loss of many fire department assets and the lack of usable water in the hydrant system.<ref name="McA-304" /> The city mains had also been the only supply for the sprinklers on the lowest 20 floors. Fires on the 7th to 13th floors therefore went unchecked by sprinklers.<ref name="McA-77" /><ref name="McA-78" />

== Maintenance, information and limits ==

A hydrant only helps if crews can reach it and it works when needed. The International Fire Engineering Guidelines list perimeter roads for fire service access and equipment such as hydrants among the items whose design and maintenance effective intervention needs.<ref name="IFEG-1.9-8">National Research Council of Canada et al. (2005), p. 1.9-8.</ref> In some jurisdictions, essential safety provisions may secure that maintenance.<ref name="IFEG-1.9-8" /> The guidelines also note that the fire service part of a design may change over a building's life, through changes in fire stations, budgets, equipment and traffic.<ref name="IFEG-1.9-2">National Research Council of Canada et al. (2005), p. 1.9-2.</ref> The 2013 commentary on C/VM2 reads New Zealand Building Code clause C5.8 as requiring hydrants and other fire safety systems to meet acceptable standards for design, construction, installation and maintenance.<ref name="MBIE13-35">Ministry of Business, Innovation and Employment (2013), p. 35.</ref>

Firefighters also need to know what each connection serves. New Zealand's clause C5.7 requires clear information so that firefighters can locate the fire and identify the fire safety systems in the building.<ref name="MBIE-53" /> It also requires information on any hazardous substances or processes in the building.<ref name="MBIE-53" /> In New York, colour-coded caps showed whether a fire department connection fed a standpipe, a sprinkler system, a combined system or a high-pressure supply.<ref name="McA-77" /> The operations and maintenance manual of WTC 7 included a riser diagram showing the arrangement of the valves.<ref name="McA-78" />

''Introduction to Fire Safety Engineering'' stresses that a positive result of a fire safety engineering analysis does not mean the fire service will attack from inside.<ref name="VR-9.3">Van Rossum (2027), §9.3 (Results from zone models).</ref> That decision always rests with the crews at the scene.<ref name="VR-9.3" /> The International Fire Engineering Guidelines likewise state that the analysis of occupant evacuation should not rely on fire service intervention.<ref name="IFEG-1.9-1">National Research Council of Canada et al. (2005), p. 1.9-1.</ref> It is misleading to give hydrants a fixed score in a risk checklist. The SFPE Handbook notes that the relative value of hydrants, sprinklers and extinguishers depends on other features of a building's form and use.<ref name="WH-5-5">Watts and Hall (2002), p. 5-5.</ref>

== See also ==

* [[Hose reel]]
* [[Fire extinguisher]]
* [[Firefighting lift]]
* [[Fire classes]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lawson, J. R., & Vettori, R. L. (2005). ''The emergency response operations'' (NIST NCSTAR 1-8). National Institute of Standards and Technology.
* McAllister, T. P., Gann, R. G., Averill, J. D., Gross, J. L., Grosshandler, W. L., Lawson, J. R., McGrattan, K. B., Pitts, W. M., Prasad, K. R., Sadek, F. H., & Nelson, H. E. (2008). ''Structural fire response and probable collapse sequence of World Trade Center Building 7'' (NIST NCSTAR 1-9, Vols. 1–2). National Institute of Standards and Technology.
* Ministry of Business, Innovation and Employment. (2013). ''Commentary for Building Code clauses C1–C6 and Verification Method C/VM2''.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Titus, J. J. (2002). Hydraulics. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-44–4-71). National Fire Protection Association; Society of Fire Protection Engineers.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Firefighting & Fire Service]]

Fire extinguisher

2026-11-02T18:35:40Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

A '''fire extinguisher''' is a portable device, carried by hand or on wheels, that holds a limited supply of extinguishing agent for attacking a fire while it is still small.<ref name="SH126">Scheffey and Hickey (2002), p. 4-126.</ref><ref name="G155">Grant (2002), p. 4-155.</ref> Extinguishers contain water, foam, dry chemical powder, carbon dioxide, wet chemical solutions or halon. Each [[Extinguishing agent]] works in its own way and suits some fires better than others.<ref name="ISB15">Iqbal and Salley (2004), p. B-15.</ref><ref name="ISB16">Iqbal and Salley (2004), p. B-16.</ref> In the United States, the rating on an extinguisher combines a number for its relative effectiveness with letters for the [[Fire classes]] on which it was found to be effective.<ref name="ISF25">Iqbal and Salley (2004), p. F-25.</ref>

Extinguishers belong to manual fire suppression, which people carry out with portable extinguishers, hoses or manually operated fixed systems.<ref name="ISF29">Iqbal and Salley (2004), p. F-29.</ref> A report of the US Nuclear Regulatory Commission describes a fire in its earliest stage as one that portable extinguishers or small hoses can still control without protective clothing or breathing apparatus.<ref name="ISF38">Iqbal and Salley (2004), p. F-38.</ref> Incident reviews describe fires that defeated several extinguishers but were then put out quickly with water.<ref name="ISH21">Iqbal and Salley (2004), p. H-21.</ref><ref name="ISH29">Iqbal and Salley (2004), pp. H-29–H-30.</ref> Fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they are specially trained.<ref name="IFEG177">National Research Council of Canada et al. (2005), p. 1.7-7.</ref>

== How an extinguisher works ==

An extinguisher stores its agent under pressure, or together with a gas that drives it out. Dry chemical powder consists of fine particles coated to prevent caking, and an inert gas projects the powder onto the fire.<ref name="ISB55">Iqbal and Salley (2004), p. B-55.</ref> Carbon dioxide is stored as a gas liquefied under pressure and provides its own pressure for release.<ref name="ISB41">Iqbal and Salley (2004), p. B-41.</ref> A portable extinguisher with aqueous film-forming foam closely resembles a stored-pressure water extinguisher, except for its special nozzle.<ref name="SH126" />

Sizes vary widely. Aqueous film-forming foam extinguishers are usually available as hand-portable models of 9 litres and as wheeled models holding 125 litres.<ref name="SH126" /> The supply of agent is limited. At one US nuclear power plant, three portable extinguishers together discharged about 32 kg (70 pounds) of dry chemical on a small fire of rags and debris.<ref name="ISH29" />

The technology has changed over time. Carbon tetrachloride became available as early as 1907 and was used mostly in hand-pump portable extinguishers, because it conducted little electricity and left no residue. It caused a number of accidental deaths and serious injuries through its toxicity, and its use was halted during the 1950s.<ref name="G150">Grant (2002), p. 4-150.</ref> Methyl bromide, which was found in the late 1920s to be more effective than carbon tetrachloride, was never used in portable extinguishers because of its high toxicity.<ref name="G150" />

Chemical foam extinguishers, in which a reaction between sodium bicarbonate and aluminium sulphate produced the foam and pushed it out, are now generally regarded as obsolete. Their manufacture in the United States stopped in 1969, and the National Fire Protection Association (NFPA) recommends replacing them.<ref name="ISB63">Iqbal and Salley (2004), p. B-63.</ref><ref name="SH126" /> The US Army also introduced portable extinguishers with halon 1301. Under the Montreal Protocol, however, the production of halons in the developed countries ended on 31 December 1993.<ref name="G151">Grant (2002), p. 4-151.</ref><ref name="DN173">DiNenno (2002), p. 4-173.</ref>

== Agents and what they do ==

NUREG-1805, a report of the US Nuclear Regulatory Commission, names four ways to put out a fire. They are separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or flame, and adding chemicals that change the combustion chemistry. More often several of these act at once.<ref name="ISB15" /> Water cools a burning solid, so that it gives off less flammable gas, and cools the flame.<ref name="ISB15" /> It is the most commonly used extinguishing agent, mainly because it is widely available and inexpensive and absorbs a great deal of heat as it turns into steam.<ref name="FL72">Fleming (2002), p. 4-72.</ref>
[[File:fse-fire-extinguisher-v1.svg|thumb|upright=1.5|alt=Portable agents cool, blanket, coat, inhibit chemistry or reduce oxygen.|Portable extinguishers use several different extinguishing mechanisms. Based on Iqbal and Salley (2004), pp. B-15–B-16.]]

Water also has clear limits. It is unsuitable for certain water-reactive materials, with which it can produce heat, flammable or toxic gases, or explosions.<ref name="FL72" /> Burning hydrocarbon fuels float on water and keep burning, and water under very hot oil turns to steam and throws out burning oil.<ref name="FL72" /><ref name="ISB58">Iqbal and Salley (2004), p. B-58.</ref> [[Firefighting foam]] overcomes the floating problem by forming a layer on the liquid that keeps out air and stops the fuel from evaporating.<ref name="SC88">Scheffey (2002), p. 4-88.</ref> Foam is water-based, however, so it shares the risk of electric shock from live equipment.<ref name="ISB60">Iqbal and Salley (2004), p. B-60.</ref>

Dry chemical powders are very common in manual extinguishers, and their most common use is on relatively small flammable liquid fires.<ref name="ISB56">Iqbal and Salley (2004), p. B-56.</ref> Common types include sodium bicarbonate, potassium bicarbonate and monoammonium phosphate, which is known as "ABC" or multipurpose powder.<ref name="ISB55" /> The powders probably act mainly by removing reactive chemical species from the flame, and they also absorb heat and block radiation.<ref name="ISB56" /> Monoammonium phosphate also forms a glassy coating over the burning surface, which makes it the only common powder considered effective against deep-seated fires.<ref name="ISB56" />

Carbon dioxide is an electrically non-conductive inert gas that is suitable for Class B and Class C fires. It puts out a fire by lowering the concentration of oxygen, of fuel vapour or of both until combustion stops.<ref name="ISF12">Iqbal and Salley (2004), p. F-12.</ref> It has a long history as an extinguishing agent, mainly for flammable liquid fires and fires in electrical equipment.<ref name="ISB41" /> Wet chemical agents, solutions of water with potassium carbonate, potassium acetate or potassium citrate, are listed in NUREG-1805 for cooking oil and fat fires.<ref name="ISF70">Iqbal and Salley (2004), p. F-70.</ref><ref name="ISB16" />

== Classes and ratings ==

The fire classes used in the United States come from NFPA 10, Standard for Portable Fire Extinguishers. Its 2002 edition, as summarised in NUREG-1805, has five classes. Class A covers ordinary combustibles such as wood, paper and many plastics, Class B flammable liquids and gases, and Class C energised electrical equipment. Class D covers combustible metals, and Class K cooking appliances with vegetable or animal oils and fats.<ref name="NFPA10">National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-13.</ref> The halon chapter of the SFPE Handbook of Fire Protection Engineering (third edition, 2002) shows only four classes, A to D, so the letters depend on the document and its edition.<ref name="G153">Grant (2002), p. 4-153.</ref>

The rating number shows relative effectiveness, and the letters show the classes of fire on which the extinguisher has been found to be effective.<ref name="ISF25" /> Ratings are based on standardised tests developed by Underwriters Laboratories.<ref name="ISF23">Iqbal and Salley (2004), p. F-23.</ref> A hand-portable foam extinguisher of 9 litres, for example, is rated 3A:20B, and a wheeled unit of 125 litres is rated 20A:160B.<ref name="SH126" /> For Class C the rating reflects the non-conductive properties of the agent. Once electrical equipment has been de-energised, extinguishers designed for Class A or Class B fires can be used safely.<ref name="ISB16" /><ref name="NFPA10" />

The class table in NUREG-1805 shows why the letters matter. It states that water and water-based extinguishers should never be used on Class D metal fires, and that a Class D extinguisher must suppress the fire without reacting physically or chemically with the metal.<ref name="ISB16" /> Among the powders, monoammonium phosphate is not recommended for kitchen fires involving hot fat because it is acidic; an alkaline powder such as potassium bicarbonate is preferred.<ref name="ISB56" />

== Role in fire protection ==

Portable extinguishers are one layer among several. The US Nuclear Regulatory Commission's defence-in-depth approach aims to prevent fires, to detect, control and extinguish quickly those that do occur, and to protect safety functions if a fire is not put out promptly.<ref name="IS12">Iqbal and Salley (2004), p. 1-2.</ref> Portable extinguishers form part of the second layer, together with detectors, fixed suppression systems, hose stations, hydrants and fire brigades. The approach recognises that the first two layers are not always entirely successful.<ref name="IS12" />

In the same handbook, Grant gives an example for a computer room in which each stage of a fire has its own control measure. Portable extinguishers, together with an automatic halon system, serve the incipient stage, while automatic sprinklers serve the stage before flashover.<ref name="G155" /> A US fire risk method for nuclear power plants similarly notes that small fires are likely to be put out immediately with portable extinguishers.<ref name="NW1117">Nowlen et al. (2005b), p. 11-17.</ref> A fire has moved beyond this early stage when firefighters need thermal protective clothing or breathing apparatus, or have to crawl to stay below the smoke and heat.<ref name="ISF38" />

Extinguishers and an automatic [[Sprinkler system]] complement each other. NUREG-1805 notes that human response, such as discovering the fire and the travel of a fire brigade, usually takes much longer than the time sprinklers need to control a fire in its early stages.<ref name="IS101">Iqbal and Salley (2004), p. 10-1.</ref> In its study of the World Trade Center, the US National Institute of Standards and Technology (NIST) noted that the sprinklers there were designed to control fires. Manual intervention with hand-held extinguishers or hose lines was generally needed to put out all of the burning, especially in areas shielded from the sprinkler spray.<ref name="EV9">Evans et al. (2005), p. 9.</ref>

In fire engineering design, the International Fire Engineering Guidelines (2005 edition) count manual suppression equipment among the measures for detection, warning and suppression.<ref name="IFEG1210">National Research Council of Canada et al. (2005), p. 1.2-10.</ref> Suppression by building occupants, using extinguishers and [[Hose reel|hose reels]], may be taken into account if appropriate criteria are used.<ref name="IFEG171">National Research Council of Canada et al. (2005), p. 1.7-1.</ref> The guidelines add that it is customary to assume that occupants will not engage in effective firefighting unless they belong to a specially trained site emergency response crew.<ref name="IFEG177" /> Professional [[Firefighting]] by the fire service is treated separately.<ref name="IFEG177" />

== People and training ==

Whether an extinguisher is used depends on the people present. In the SFPE Handbook, Bryan describes how a person who has recognised a fire evaluates the threat. The person then either evacuates the building or fights the fire, for example by fetching an extinguisher or operating a manual fire alarm.<ref name="BR318">Bryan (2002), pp. 3-318–3-319.</ref> People with firefighting training or experience, in surroundings they know, are likely to choose more adaptive actions. In one office building fire, regular occupants fought the fire and alerted others, while visitors attending training sessions mostly evacuated.<ref name="BR318" />

Studies of residential and other fires give an idea of how often people fight fires. In a British study of 2,193 people in 952 fires, 14.7 percent showed firefighting behaviour, against 22.9 percent of 584 people in 335 mainly residential fires in a US study.<ref name="BR322">Bryan (2002), pp. 3-322–3-323.</ref> In the US study, fetching an extinguisher was the first action of 4.6 percent of the participants.<ref name="BR322" />

In US nuclear power plants, a fire watch is a person who provides extra cover, for example during hot work, or makes up for an impaired fire protection system. Fire watches should be trained to recognise fire hazards, to use fire extinguishers and to follow notification procedures.<ref name="ISF29" /> A US method for counting fire events treats a fire as potentially challenging when a hose stream, several portable extinguishers or a fixed suppression system were needed.<ref name="NWC9">Nowlen et al. (2005b), pp. C-8–C-9.</ref> A hot-work fire also counts if active intervention was needed, even when the fire watch put it out quickly, although the use of a single extinguisher should not be the only indicator.<ref name="NWC9" />

== Requirements and maintenance ==

Requirements for extinguishers depend on the code or standard that applies and on its edition. In the United States, NUREG-1805 lists NFPA 10, Standard for Portable Fire Extinguishers (2002 edition), among the current NFPA standards. It notes that NFPA codes are revised on cycles of 3 to 5 years, so the edition in force at the time of design is the code of record.<ref name="ISE1">Iqbal and Salley (2004), p. E-1.</ref> The SFPE Handbook refers to NFPA 10 for the selection and placement of portable extinguishers.<ref name="SH126" /> Citing NFPA 10 and a handbook chapter on extinguisher use and maintenance, NUREG-1805 describes three hazard levels by the amount of Class A and B materials present. Light hazard can include offices and classrooms, ordinary hazard shops and parking garages, and extra hazard woodworking, vehicle repair and cooking areas.<ref name="ISB14">Conroy (1997) and National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-14.</ref>

New York City shows how requirements can sit in different documents. NIST found that the 1968 New York City Building Code had no requirements for fire extinguishers, because it required occupant hose reels instead.<ref name="LEW151">Lew et al. (2005), p. 151.</ref> For the World Trade Center, the Port Authority nevertheless required portable extinguishers in all spaces. It followed a Fire Department of New York directive of 17 September 1980 and section 27-4009 of the New York City Fire Prevention Code of 1 July 1988.<ref name="GJ17">Grill and Johnson (2005c), p. 17.</ref>

Maintenance is part of [[Fire safety management]]. The International Fire Engineering Guidelines state that active fire protection equipment, including suppression equipment, needs particular attention to ensure proper installation, commissioning, management and use. Its maintenance should follow the relevant codes, standards and manufacturer's literature.<ref name="IFEG178">National Research Council of Canada et al. (2005), p. 1.7-8.</ref> The New Zealand part of the guidelines adds that the fire safety of a building depends on the ongoing functioning of its fire safety system. Inspection, testing and maintenance programmes should therefore have due regard to New Zealand standards and legislation.<ref name="IFEGNZ">National Research Council of Canada et al. (2005), p. 0.3-8 (Part 0, New Zealand).</ref> Among the information notices of the Nuclear Regulatory Commission listed in NUREG-1805 is one of 11 April 2001 titled "Neglected Fire Extinguisher Maintenance Causes Fatality".<ref name="ISD14">Iqbal and Salley (2004), p. D-14.</ref>

== Limits, side effects and incident experience ==

Dry chemical powder has side effects. Its sudden release and unexpected re-ignition of the fire are hazards, and although the powders are non-toxic, they can cause temporary breathing difficulty and reduce visibility.<ref name="ISB57">Iqbal and Salley (2004), p. B-57.</ref> All powders need significant cleaning after use, and some corrosion or damage is possible.<ref name="ISB56" /> Powders become sticky when heated, and applying water to the residue speeds up the corrosion of equipment.<ref name="ISH29" />

At the Point Beach 1 nuclear power plant in 2001, three portable dry chemical extinguishers failed to put out a small fire, which re-ignited twice. The fire brigade then put it out easily with about 57 to 76 litres (15 to 20 gallons) of water from a hose line.<ref name="ISH29" /> White powder covered about half of the containment basement floor, and NUREG-1805 concludes that the cleanup effort called for a more careful choice of extinguishing agent.<ref name="ISH29" />
[[File:fse-fire-extinguisher-v3.svg|thumb|upright=1.5|alt=Powder clouds reduce visibility, coat equipment and require cleanup while hot fuel can reflash.|Extinguishing also creates post-discharge hazards and restoration needs. Based on Iqbal and Salley (2004), pp. H-29–H-30.]]

Fires in energised electrical equipment have repeatedly defeated portable extinguishers in US nuclear power plants. At Waterford 3 in 1995, attacks with carbon dioxide, halon and dry chemical extinguishers failed. Water was permitted only about 90 minutes after the fire started, and the fire was then under control within 4 minutes.<ref name="ISH21" /> At Prairie Island 1 in 2001, more than 20 portable carbon dioxide extinguishers were used over about 1.5 hours on a breaker fire, and two fire brigade members were treated for heat exhaustion.<ref name="ISH30">Iqbal and Salley (2004), pp. H-30–H-31.</ref> A review of high-energy arcing faults in electrical switchgear notes that in severe events the first extinguishers may be ineffective whatever the agent, and that such fires were finally put out with water.<ref name="NWM3">Nowlen et al. (2005b), p. M-3.</ref>

Delivery is a further limit. In a deep-seated fire, [[Smouldering]] continues below the surface, where an agent cannot easily reach the seat of the fire.<ref name="ISB39">Iqbal and Salley (2004), pp. B-39–B-40.</ref> A gaseous agent can put out the visible flames at once while glowing combustion continues inside, and the fire can then re-ignite when air returns.<ref name="ISB43">Iqbal and Salley (2004), p. B-43.</ref> Low-expansion foam works well on a flat pool fire but is not particularly effective on running fuel or a pressurised spray.<ref name="SC88" />
[[File:fse-fire-extinguisher-v2.svg|thumb|upright=1.5|alt=Extinguisher discharge reaches a pool but leaves shielded and deep fuel hot.|Manual extinguishing depends on delivery, coverage and remaining fuel condition. Based on Scheffey (2002), p. 4-88 and Iqbal and Salley (2004), pp. B-43–B-44.]]

Gaseous agents also have hazards of their own. [[Carbon dioxide]] replaces the oxygen in the air, and people become unconscious at a concentration of 10 percent by volume.<ref name="ISB41" /> Grant notes that the high concentrations needed to extinguish a fire with carbon dioxide make the protected space lethal to people.<ref name="G155" /> In battery rooms with lead-acid batteries, NUREG-1805 advises against discharging an extinguisher directly onto a battery, because the thermal shock may crack its case or cover.<ref name="IS1611">Iqbal and Salley (2004), p. 16-11.</ref>

== See also ==

* [[Hot work]]
* [[Dry and wet risers]]
* [[Fire hydrant]]

== Notes ==

<references />

== References ==

* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* DiNenno, P. J. (2002). Halon replacement clean agent total flooding systems. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-173–4-200). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Grant, C. C. (2002). Halon design calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-149–4-172). National Fire Protection Association; Society of Fire Protection Engineers.
* Grill, R. A., & Johnson, D. A. (2005c). ''Post-construction modifications to fire protection and life safety systems of the World Trade Center towers'' (NIST NCSTAR 1-1H). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-88–4-122). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L., & Hickey, H. E. (2002). Foam system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-123–4-148). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Firefighting & Fire Service]]

Fire classes

2026-11-02T18:35:34Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

'''Fire classes''' are letter categories that sort fires by the kind of material that is burning, such as ordinary combustibles, flammable liquids and gases, energised electrical equipment and reactive metals.<ref name="G153">Grant (2002), p. 4-153.</ref> A report of the US Nuclear Regulatory Commission, NUREG-1805, adds that the letter gives a general indication of the type and severity of the hazard.<ref name="ISB13">Iqbal and Salley (2004), p. B-13.</ref> The classes are used to match a fire with a suitable [[Extinguishing agent]] and [[Fire extinguisher]]. Water, foam, dry chemical powders and gases work in different ways, and some of them make certain fires worse.<ref name="ISB15">Iqbal and Salley (2004), p. B-15.</ref><ref name="ISB16">Iqbal and Salley (2004), p. B-16.</ref>

Class letters are set by standards, and they are not the same in every document. The SFPE Handbook of Fire Protection Engineering (third edition, 2002) shows four classes, A to D, taken from a 1991 handbook of the US National Fire Protection Association (NFPA).<ref name="G171">Grant (2002), pp. 4-153 and 4-171.</ref> The 2002 edition of the US standard NFPA 10, as summarised in NUREG-1805, adds Class K for cooking oils and fats.<ref name="NFPA10">National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-13.</ref>

The wrong agent can increase the hazard. NUREG-1805 states that water should never be used on burning metals, that water under very hot cooking oil can throw out burning oil, and that water-based agents on live equipment can cause electric shock.<ref name="ISB16" /><ref name="ISB58">Iqbal and Salley (2004), p. B-58.</ref><ref name="ISB60">Iqbal and Salley (2004), p. B-60.</ref> Even an agent listed for the right class can fail on smouldering deep inside a solid or on a running liquid fire.<ref name="ISB43">Iqbal and Salley (2004), p. B-43.</ref><ref name="SC88">Scheffey (2002), p. 4-88.</ref>

== How fire classes are defined ==

[[Combustion]] is a set of mainly heat-releasing chemical reactions between a fuel and an oxidiser, usually the oxygen in air, which produce heat and light as a flame or a glow.<ref name="VR41">Van Rossum (2027), §4.1.</ref> Solids and liquids do not burn directly but only once they have turned into gas. A liquid first evaporates, as in a pool fire, while a solid first breaks down by [[Pyrolysis]] into smaller molecules that escape as gas and burn in the flames.<ref name="VR41" /> The class system groups fires according to the type of fuel and the possible spread of the fire.<ref name="ISB13" />

The [[Fire triangle]] names the three factors that combustion needs: fuel, oxygen and a high enough temperature.<ref name="VR42">Van Rossum (2027), §4.2.</ref> Air contains about 21 percent oxygen by volume. When the oxygen level falls, a fire may stop spreading and eventually go out, depending on the exact concentration.<ref name="VR42" /> Typical extinguishing removes one side of the triangle by taking away the fuel, limiting the oxygen (smothering) or removing the heat (quenching).<ref name="G152">Grant (2002), pp. 4-152–4-153.</ref> Halons instead break up the chain reaction of the flame, so the triangle was extended into a "tetrahedron of fire" with the chain reaction as a fourth element.<ref name="G152" />

NUREG-1805 lists four ways to put out a fire: separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or the flame, and adding chemicals that change the combustion chemistry.<ref name="ISB15" /> More often several of these act at once, and their relative importance changes with the circumstances.<ref name="ISB15" /><ref name="ISB16" /> Water on a burning solid cools the solid, so that it gives off less flammable gas, and cools the flame, so that less heat returns to the fuel. In a confined space the steam may also keep oxygen away, and a fine water fog may block radiant heat.<ref name="ISB15" /> Dry chemical powder may interfere with the flame chemistry, coat the fuel surface, cool the flame and block radiation.<ref name="ISB15" />

== Classes in United States documents ==

In the United States, NFPA 10, Standard for Portable Fire Extinguishers (2002 edition), as summarised in NUREG-1805, divides fires into five classes according to the fuel involved.<ref name="NFPA10" /> Class A covers ordinary combustible materials such as wood, cloth, paper, rubber and many plastics. Class B covers flammable or combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols and flammable gases. Class C covers fires in energised electrical equipment, where it matters that the extinguishing agent does not conduct electricity. Class D covers combustible metals such as magnesium, titanium, zirconium, sodium, lithium and potassium. Class K covers cooking appliances that use vegetable or animal oils and fats.<ref name="NFPA10" />
[[File:fse-fire-classes-v1.svg|thumb|upright=1.5|alt=Five US classes cover ordinary solids, liquids, energised equipment, metals and cooking media.|The five US fire classes of NFPA 10 (2002 edition), as summarised in NUREG-1805. Based on Iqbal and Salley (2004), pp. B-13 and B-16.]]

Other US documents use fewer letters. The SFPE Handbook chapter on halon design calculations shows four classes of fire: ordinary combustibles (Class A), flammable liquids and gases (Class B), electrical equipment (Class C) and reactive metals (Class D).<ref name="G153" /> This grouping, which the chapter takes from the seventeenth edition of the NFPA Fire Protection Handbook (1991), has no separate class for cooking oils and fats.<ref name="G171" /> A class letter therefore only has a clear meaning together with the name and edition of the document that defines it.

NUREG-1805 also lists extinguishing agents for each class. It names water, dry chemicals, foam and some halon for Class A, and carbon dioxide, dry chemical agents, halon and foam for Class B.<ref name="ISB16" /> For Class C it names carbon dioxide, dry chemical agents and halon, for Class D only dry chemical agents, and for Class K dry chemical agents, carbon dioxide and wet chemical agents.<ref name="ISB16" /> The halon entries need care, because the same report calls halon obsolete for fire protection owing to its possible effect on the ozone layer.<ref name="ISF35">Iqbal and Salley (2004), p. F-35.</ref> Under the Montreal Protocol, the production of halons in the developed countries ended on 31 December 1993.<ref name="DN173">DiNenno (2002), p. 4-173.</ref>

== Class A: ordinary combustibles ==

Class A fires burn ordinary solid materials such as wood, cloth, paper, rubber and many plastics.<ref name="NFPA10" /> Water is the most commonly used extinguishing agent, mainly because it is widely available and inexpensive. It also absorbs a large amount of heat as it warms up and turns into steam.<ref name="FL72">Fleming (2002), p. 4-72.</ref> Fleming gives 9280 Btu for one US gallon of water heated from a room temperature of 21 °C to steam at 100 °C, which is almost 2.6 MJ for every litre.<ref name="FL72c">Fleming (2002), p. 4-72 (9280 Btu per US gallon, converted to SI).</ref>

Two kinds of burning can occur in Class A materials. In flaming combustion the hot fuel surface gives off gases that burn in the flame, while in [[Smouldering]] or glowing combustion the material reacts with oxygen at its surface or inside the fuel mass.<ref name="ISB39">Iqbal and Salley (2004), p. B-39.</ref> Smouldering cannot be put out as quickly as flaming, and it can continue for weeks in bales of cotton or in heaps of sawdust. It stops only when the oxygen or the fuel runs out or the fuel becomes too cool to react. It is usually extinguished by cooling with water or by covering the fuel with an inert gas.<ref name="ISB39" />

A deep-seated fire is smouldering below the surface that may continue for some time after the surface flames have been suppressed.<ref name="ISB39" /> Halon 1301 at the normal concentration of 5 to 6 percent puts out the visible flames at once. Glowing combustion inside the material may continue, however, and re-ignite when the space is ventilated again.<ref name="ISB43" /> Grant notes that complete extinguishment needs far higher concentrations of 18 to 30 percent, which are seldom economical.<ref name="G153" /> NUREG-1805 states that the interior of the material must be investigated once the surface fire has been put out.<ref name="ISB39" />

Dry chemical powders show the same limit. All seven common types suppress flames, but only monoammonium phosphate, known as "ABC" or multipurpose powder, is considered effective against deep-seated fires. It forms a glassy coating over the burning surface.<ref name="ISB55">Iqbal and Salley (2004), pp. B-55–B-56.</ref> The class can also hide differences between materials. Many plastics belong to Class A, yet Grant notes that most plastics behave like flammable liquids under halon 1301 and are put out rapidly at 4 to 6 percent. Cellulosic (plant-fibre) products, in contrast, can in certain forms develop deep-seated fires.<ref name="G153" />

== Class B: flammable liquids and gases ==

Class B fires involve flammable or combustible liquids and flammable gases.<ref name="NFPA10" /> The NUREG-1805 table describes the class as flammable liquids, gases and liquid-derived solids, with examples such as gasoline (petrol), oils, liquefied petroleum gas, heavy lubricants and grease.<ref name="ISB16" /> Water is a poor agent for many of these fires. It is denser than most hydrocarbon fuels and does not mix with them, so the burning fuel floats on top of the water, keeps burning and may spread.<ref name="FL72" />

[[Firefighting foam]] consists of air-filled bubbles made from a solution of foam concentrate in water, typically at 1, 3 or 6 percent concentrate.<ref name="SC88" /> The foam is lighter than the fuel and floats on it. It forms an air-excluding layer that stops the fuel from evaporating at its surface, and when the whole surface is covered the fire goes out.<ref name="SC88" /> Film-forming foams can also spread a vapour-sealing film of water solution over most hydrocarbon fuels.<ref name="SC88" /> Foam breaks down under heat and flames, so it must be applied at a sufficient rate and in sufficient volume to keep a layer over the fuel.<ref name="ISB59">Iqbal and Salley (2004), p. B-59.</ref>

Liquids that mix with water, such as alcohols, need a different approach. Enough water can dilute them until they no longer burn, but for a deep pool of alcohol this can take so long that a foam is the better choice.<ref name="ISB58" /> Foams for alcohol fires must be alcohol resistant. Their concentrates form a floating polymer skin that protects the foam from breakdown by polar solvents such as acetone, methanol and ethanol.<ref name="ISB59" /><ref name="SC89">Scheffey (2002), p. 4-89.</ref>

The shape of a liquid fire matters as much as the fuel. Low-expansion foams have at most ten times the volume of the solution they are made from. They work well on flat pool fires but are not particularly effective on three-dimensional fires, such as running fuel or a pressurised spray.<ref name="SC88" /> This is particularly true when the fuel has a low flash point, and for such fires an auxiliary agent such as dry chemical powder is typically used with the foam.<ref name="SC88" /> Dry chemical agents are themselves used most often on relatively small flammable liquid fires.<ref name="ISB56">Iqbal and Salley (2004), p. B-56.</ref> Halon 1301 works well on liquid fires inside a closed space, but on a large outdoor running pool fire it dissipates without reaching the flames.<ref name="G153" />
[[File:fse-fire-classes-v2.svg|thumb|upright=1.5|alt=Foam blankets a pool, while running fuel and a pressurised spray lack a continuous cover.|Liquid-fire geometry affects the usefulness of a foam blanket. Based on Scheffey (2002), p. 4-88 and Fleming (2002), p. 4-72.]]

== Class C: energised electrical equipment ==

Class C differs from the other classes because it does not add a new fuel. NUREG-1805 describes it as the same fuels as Class A and B fires together with energised electrical equipment, such as household appliances.<ref name="ISB16" /> The class exists because the agent must not conduct electricity, and extinguishers for Class C fires are rated by the non-conductive properties of their agent.<ref name="NFPA10" /><ref name="ISB16" /> Once the equipment has been de-energised, extinguishers designed for Class A or Class B fires can be used safely.<ref name="NFPA10" />

Water and water-based agents, including foam, carry a risk of electric shock when they reach live equipment.<ref name="ISB60" /> Carbon dioxide is an electrically non-conductive gas that is suitable for Class B and Class C fires. It puts out a fire by lowering the concentration of oxygen, of fuel vapour or of both until combustion stops.<ref name="ISF12">Iqbal and Salley (2004), p. F-12.</ref> Halon 1301 is particularly suited to Class B and Class C fires, and electrical and electronic equipment is typically protected with a concentration of 5 percent.<ref name="G153" /> Dry chemical powder is safe on electrical fires from the point of view of electric shock. The powders can, however, damage delicate electrical equipment, especially monoammonium phosphate, which is notably acidic and corrodes more readily than the others.<ref name="ISB56" />

NUREG-1805 reviews US nuclear power plant fires in which crews avoided water on live equipment. At Waterford 3 in 1995, a switchgear fire was attacked with portable carbon dioxide, halon and dry chemical extinguishers without success. Water was only permitted about 90 minutes after the fire started, and firefighters then brought the fire under control within 4 minutes.<ref name="ISH21">Iqbal and Salley (2004), p. H-21.</ref> The report notes that the fire was allowed to burn far longer, and the damage was perhaps made worse, than with prompt and effective suppression.<ref name="ISH23">Iqbal and Salley (2004), p. H-23.</ref>

At Prairie Island 1 in 2001, a first attempt to de-energise a burning breaker failed, as arcing showed, and the decision not to use water on the live equipment complicated the attack.<ref name="ISH30">Iqbal and Salley (2004), pp. H-30–H-31.</ref> The fire took about 1.5 hours and more than 20 portable carbon dioxide extinguishers to put out. The report concludes that operating experience with fires in energised electrical equipment shows a relatively small quantity of water to have been effective.<ref name="ISH30" />

== Classes D and K: metals and cooking oils ==

Class D covers fires in combustible metals or in metal alloys with combustible metal components.<ref name="ISB16" /> Metals such as magnesium, titanium, sodium, potassium, lithium and zirconium ignite easily as thin sections, fine particles or molten metal. As a solid block, however, they are comparatively hard to ignite.<ref name="ISB29">Iqbal and Salley (2004), p. B-29.</ref> Even aluminium, iron and steel can burn when finely divided, and clean fine steel wool may ignite. Burning metals can be hotter than burning flammable liquids, and some keep burning in carbon dioxide, nitrogen, water or steam.<ref name="ISB29" />

Water is not usually recommended, because several metals react with water to release hydrogen, which burns rapidly. Water entering molten metal can also cause violent steam explosions.<ref name="ISB31">Iqbal and Salley (2004), p. B-31.</ref> The class table in NUREG-1805 states that water and water-based extinguishers should never be used on Class D fires.<ref name="ISB16" /> Its text nevertheless reports that large quantities of water have put out small quantities of burning magnesium when no pools of molten metal were present.<ref name="ISB31" /> Fleming likewise notes that enough water can overcome the reaction of minor amounts of water-reactive materials.<ref name="FL72" />

To work on a Class D fire, an extinguisher must suppress the fire without reacting physically or chemically with the metal.<ref name="ISB16" /> NUREG-1805 lists special powders, each for particular metals, and notes that only argon and helium are acceptable inert gases for metals that react with nitrogen or carbon dioxide.<ref name="ISB31" /> Halons should not be used on metal fires. Grant notes that reactive metals burn so intensely that they overpower halon 1301.<ref name="ISB31" /><ref name="G152" />

Class K covers cooking appliances that use vegetable or animal oils and fats.<ref name="NFPA10" /> When burning oil is much hotter than the boiling point of water, water applied to it penetrates the oil and turns into steam below the surface. The resulting eruption of oil, a [[Boilover]], speeds up the burning and may spread the fire.<ref name="ISB58" /> Foam carries a similar risk, because on a liquid at 100 °C or above the steam can expand the foam fourfold and cause boilover.<ref name="ISB60" />

For this class NUREG-1805 lists dry chemical agents, carbon dioxide and wet chemical agents.<ref name="ISB16" /> A wet chemical agent is a solution of water with potassium carbonate, potassium acetate or potassium citrate. Wet chemical systems are used mainly for cooking range hoods, ducts and the associated appliances.<ref name="ISF70">Iqbal and Salley (2004), p. F-70.</ref> Among the powders, monoammonium phosphate is not recommended for kitchen fires involving hot fat because it is acidic, and an alkaline powder such as potassium bicarbonate is preferred.<ref name="ISB56" />

== How the classes are used ==

In the United States, the class letters appear in the rating marked on an extinguisher. NUREG-1805 describes the NFPA 10 rating as a number, such as 5, 20 or 70, that shows relative effectiveness. The number is followed by one or more letters for the classes of fire on which the extinguisher was found to be effective.<ref name="ISF25">Iqbal and Salley (2004), p. F-25.</ref> The rating is based on standardised tests developed by Underwriters Laboratories.<ref name="ISF23">Iqbal and Salley (2004), p. F-23.</ref> One extinguisher can carry ratings for more than one class. Hand-portable extinguishers holding 9 litres of aqueous film-forming foam are rated 3A:20B, and wheeled units holding 125 litres are rated 20A:160B.<ref name="SH126">Scheffey and Hickey (2002), p. 4-126.</ref>

The classes are also linked to standard test fires. Extinguishing concentrations of gaseous agents for Class A fuels were traditionally developed with burning wood cribs, and tests with sheets of plastics have more recently been required as well.<ref name="DN177">DiNenno (2002), p. 4-177.</ref> For Class B, the US foam test standard UL 162 burns commercial n-heptane in a square pan of at least 4.6 m².<ref name="SC95">Scheffey (2002), p. 4-95.</ref>

The letters can describe the hazard of a whole space. Citing NFPA 10 and a handbook chapter on extinguisher use, NUREG-1805 describes light hazard occupancies such as offices and classrooms. These hold only a minor quantity of Class A materials and small amounts of Class B liquids in closed containers.<ref name="ISB14">Conroy (1997) and National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-14.</ref> Ordinary hazard occupancies, such as dining areas, shops and parking garages, hold larger amounts of Class A and B materials. Extra hazard occupancies, such as woodworking, vehicle repair and cooking areas, hold more than that.<ref name="ISB14" />

== Limits and common misconceptions ==

A class letter describes the fuel, not the whole fire. One fire can involve several classes at once, as Class C itself shows by combining ordinary and liquid fuels with live equipment.<ref name="ISB16" /> The same class can also cover very different fires, such as a flat pool and a pressurised spray of the same liquid, or burning plastic and a smouldering bale of cotton.<ref name="SC88" /><ref name="G153" /><ref name="ISB39" /> The choice of agent therefore depends on the form of the fuel and on the hazards of the agent itself, not only on the letter.
[[File:fse-fire-classes-v3.svg|thumb|upright=1.5|alt=Class and fuel form lead to compatibility, delivery, persistence and secondary-effect checks.|Class selection is only the first step in choosing an extinguishing agent. Based on Iqbal and Salley (2004), pp. B-15–B-16 and Scheffey (2002), p. 4-88.]]

Putting out the flames does not mean that the fire is out. Deep-seated fires can re-ignite when air returns, and NUREG-1805 names unexpected re-ignition as a hazard of dry chemical agents.<ref name="ISB43" /><ref name="ISB57">Iqbal and Salley (2004), p. B-57.</ref> At the Point Beach 1 nuclear power plant in 2001, the fire brigade discharged about 32 kg (70 pounds) of dry chemical from three portable extinguishers on a small fire of rags and debris. The fire re-ignited twice and was finally put out with about 57 to 76 litres (15 to 20 gallons) of water. The powder covered large areas of the containment building in white dust.<ref name="ISH29">Iqbal and Salley (2004), pp. H-29–H-30.</ref>

The class lists in NFPA 10 (2002 edition) and in the SFPE Handbook do not mention batteries.<ref name="NFPA10" /><ref name="G153" /> A [[Lithium-ion battery fire]] can involve [[Thermal runaway]], a failure in which a battery cell heats itself and can release flammable gases. The fire then keeps itself going and re-ignites until the energy of the battery pack has been used up.<ref name="NIPV22">Van der Graaf et al. (2021/2023), p. 22.</ref> In an electric vehicle the battery pack is sealed, so cooling water cannot reach the cells directly, and a Dutch report describes prolonged cooling with large amounts of water.<ref name="NIPV22" /> The same report states that a burning battery pack of an electric vehicle is very difficult or impossible to extinguish, and that water has to reach the inside of the pack.<ref name="NIPV30">Van der Graaf et al. (2021/2023), p. 30.</ref>

The word "class" is also used in unrelated systems, which can cause confusion. NUREG-1805 groups [[t-squared fire|t-squared fires]] into slow, medium, fast and ultra-fast growth classes.<ref name="ISB3">Iqbal and Salley (2004), pp. B-3, B-17 and C-11.</ref> Following NFPA 30, it classifies flammable liquids as Class IA, IB and IC by flash point, and following NFPA 256 it rates roof coverings as Class A, B or C by flame spread.<ref name="ISB3" /> None of these is a fire class in the sense used for choosing an extinguishing agent.

== See also ==

* [[Aqueous film-forming foam]]
* [[Firefighting]]
* [[Hose reel]]

== Notes ==

<references />

== References ==

* DiNenno, P. J. (2002). Halon replacement clean agent total flooding systems. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-173–4-200). National Fire Protection Association; Society of Fire Protection Engineers.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Grant, C. C. (2002). Halon design calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-149–4-172). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-88–4-122). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L., & Hickey, H. E. (2002). Foam system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-123–4-148). National Fire Protection Association; Society of Fire Protection Engineers.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Wildfire

2026-11-02T18:33:42Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

A '''wildfire''', also called a wildland fire or bushfire, is a fire that spreads through vegetation. It can burn the brush on a forest floor, the crowns of trees, or gorse and heather.<ref name="Q-255">Quintiere (2002b), p. 2-255.</ref><ref name="IFEG-5">National Research Council of Canada et al. (2005), p. 1.6-5.</ref> How it spreads depends on the type and arrangement of the fuel, the terrain, the wind and the humidity. The flames heat the vegetation ahead of them by radiation and convection, and the wind can carry burning embers far ahead to start new fires.<ref name="Q-255" /> Forest fires spread at rates of the order of 1 to 100 cm per second, or about 0.6 to 60 m per minute.<ref name="Q-247">Quintiere (2002b), p. 2-247.</ref> Based on its research, the US Forest Service has introduced practical methods for estimating flame spread in forests under a variety of field conditions.<ref name="Q-255" />

In fire safety engineering, the International Fire Engineering Guidelines (2005) note that flying brands and embers may have design implications in areas prone to bushfires.<ref name="IFEG-5" /> Wildfire smoke can also affect infrastructure. A US fire risk method for nuclear power plants assumes that heavy smoke from a large forest fire will make high-voltage transmission equipment trip off-line.<ref name="Nowlen">Nowlen et al. (2005b), p. T-14.</ref> Fire risk analysis counts wildland fires among the natural catastrophes that make zero fire risk unattainable.<ref name="Watts">Watts and Hall (2002), p. 5-4.</ref>

== How a wildfire spreads ==

[[Flame spread]] is the movement of a flame that stays close to the solid or liquid fuel feeding it. In natural fires, it largely decides how the fire develops.<ref name="Q-246">Quintiere (2002b), p. 2-246.</ref> Fire spread over a fuel is often seen as a chain of ignitions, in which the flame heats and ignites the material just ahead of it.<ref name="Kanury">Kanury (2002a), p. 2-229.</ref> Growth is a race between spreading and burning. If the flame spreads quickly compared with the time the fuel needs to burn out, the fire is likely to accelerate.<ref name="Q-246" />

In a forest, the porous brush on the forest floor usually burns. In severe fires the crowns of the trees burn as well, or even on their own.<ref name="Q-255" /> Like most natural fires, a forest fire burns with diffusion flames, because no burner mixes the fuel and the air beforehand.<ref name="NUREG-3-12">Iqbal and Salley (2004), p. 3-12.</ref> Its advancing front is a long, narrow line of fire that draws in air from both sides as the hot gases rise, like a row of burning townhouses.<ref name="NUREG-9-2">Iqbal and Salley (2004), p. 9-2.</ref> A brush fire is an example of a fire whose energy output is small compared with its diameter, the opposite of an oil-well blowout fire, and most ordinary accidental fires lie in between.<ref name="Najafi">Najafi et al. (2007), p. 2-27.</ref>

The SFPE Handbook gives spread rates of the order of 1 to 100 cm per second for forest and urban fires, the same order as upward flame spread on thick solids. Flames creeping sideways or downwards over a thick solid move at about 0.1 cm per second, and smouldering at only 0.001 to 0.01 cm per second.<ref name="Q-247" /> For the same heating, flames spread faster over a fuel of lower density.<ref name="Q-247" /> An approximate correlation by Thomas, quoted for wildland fires, wood cribs and urban conflagrations, makes the spread rate rise with wind speed. The rate falls as the fuel bed becomes denser.<ref name="Q-255" />

== Wind, slope and radiation ==

Flame spread in a forest depends on radiant heat transfer and on convective heating caused by the wind or by the slope of the terrain.<ref name="Q-255" /> When the flow runs in the direction of spread, the flame and its hot gases heat a stretch of unburnt fuel about as long as the flame, 0.1 to 10 m. A flame spreading against the flow heats only 1 to 3 mm ahead of it. Such wind-aided spread can accelerate and therefore appears more rapid.<ref name="Q-250">Quintiere (2002b), pp. 2-250–2-251.</ref> A slope works in a similar way, and forest fires are known to accelerate uphill because their flames lean towards the slope. Analysis of the King's Cross underground fire in London showed the same effect: flames on a wooden escalator lay down in its trench instead of rising vertically.<ref name="Cox">Cox and Kumar (2002), p. 3-207.</ref>
[[File:fse-wildfire-v1.svg|thumb|upright=1.5|alt=Wind and slope tilt flames towards uphill vegetation while a fuel gap interrupts one path.|Wildfire spread depends on fuel, terrain and wind. Based on Quintiere (2002b), p. 2-255 and Cox and Kumar (2002), p. 3-207.]]

[[Flame radiation]] preheats the fuel ahead of the front, and as the fuel warms up through radiation and convection from the fire, the spread accelerates.<ref name="Q-247" /> Radiation dominates heat transfer at high temperatures, from about 400 °C, because its intensity rises with the fourth power of the temperature.<ref name="VR-5.4">Van Rossum (2027), §5.4.</ref> How much of it reaches a target depends on the [[view factor]]. This is larger for a bigger radiating surface and smaller at a greater distance or a more oblique angle. A radiating surface of only 5 m² can fill almost the whole view of a target close to it, while the sun is enormous but too far away to have a large view factor.<ref name="VR-5.4" /> Radiation also lets a fire cross gaps, and the jump of a forest fire across a firebreak is generally viewed as ignition by radiation.<ref name="Kanury" />

== Firebrands and fuel breaks ==

[[Firebrands]] are flaming or smouldering objects carried through the air from a fire, which can sometimes ignite combustibles far away. An ember is a particle of solid material that gives off radiant energy because of its temperature or because it is burning at its surface.<ref name="NUREG-F">Iqbal and Salley (2004), pp. F-17, F-22, F-24, F-29.</ref> In a forest fire, wind currents can carry large embers great distances and start spot fires at other locations.<ref name="Q-255" />

The brands are lifted by the rising hot gases of the fire and then fall onto combustible material. This mechanism has been observed in warehouse fires and wildland fires, both of which involve cellulosic materials. In NIST tests with burning office workstations, by contrast, there was no evidence that flying brands played a role. There the fire spread through burning carpet, and in one test the video record suggests that radiation from the hot smoke layer ignited a workstation.<ref name="Hamins">Hamins, Maranghides, McGrattan, Ohlemiller, and Anleitner (2005), p. 30.</ref>
[[File:fse-wildfire-v2.svg|thumb|upright=1.5|alt=Wind carries burning brands over a fuel break to ignite a separate spot fire.|Firebrands create discontinuous spread beyond the main fire front. Based on Quintiere (2002b), p. 2-255 and Hamins, Maranghides, McGrattan, Ohlemiller, and Anleitner (2005), p. 30.]]

[[Fire spread]] through vegetation can be controlled with breaks in the fuel. The size of break needed to stop a fire depends on the size of the fire and on how it transfers heat.<ref name="Q-255" /> According to a glossary definition quoted in NUREG-1805, controlling a fire means completing a control line around it. The line also has to enclose any spot fire from it and any interior island to be saved. Unburnt areas next to the line on the fire side are also burnt out, and hot spots that threaten the line are cooled.<ref name="NUREG-F" />

Fire can also persist in the forest floor. The duff layer on a forest floor, a porous layer of decaying organic material, is often set smouldering by a passing forest fire.<ref name="Ohlemiller">Ohlemiller (2002), p. 2-206.</ref> This [[smouldering]] is very irregular in extent. It can re-ignite a flaming fire, and it also affects whether dormant seeds survive and the forest regenerates.<ref name="Ohlemiller" />

== Buildings at the wildland-urban interface ==

Where wildland borders built-up areas, at the [[wildland-urban interface]], a vegetation fire can reach buildings.<ref name="IFEG-5" /><ref name="FDS-ix">McGrattan et al. (2026), p. ix.</ref> The International Fire Engineering Guidelines (2005) list three routes for fire spread from a burning building to a neighbouring building or property boundary: burning embers and other debris, radiation, and direct flame contact.<ref name="IFEG-7">National Research Council of Canada et al. (2005), p. 1.6-7.</ref> For adjacent buildings, fire can even spread by radiation through the glass of closed windows without the glass breaking.<ref name="IFEG-7" /> The same guidance notes that flying brands and embers may need to be considered if fire spread to adjoining property is to be limited. This may have design implications in areas prone to bushfires.<ref name="IFEG-5" /> [[Fire spread between buildings]], for example across a city, involves radiant heating to ignition.<ref name="Kanury" />
[[File:fse-wildfire-v3.svg|thumb|upright=1.5|alt=Vegetation fire exposes a building by direct flames, radiant heat and firebrands.|Routes of fire spread to buildings: direct flame contact, radiation and firebrands. The guidance names these routes for fire spreading from a burning building and notes that embers may need to be considered in areas prone to bushfires. Based on National Research Council of Canada et al. (2005), pp. 1.6-5 and 1.6-7, and Quintiere (2002b), p. 2-255.]]

== Predicting wildfire spread ==

The Fire Dynamics Simulator (FDS), a computer fire model, includes a wildland fire spread model, and the US Forest Service supported the development of its sub-models for the wildland-urban interface.<ref name="FDS-ix" /> FDS can represent grasses, leaves and burning brands as particles, so that their heating and decomposition are calculated directly.<ref name="FDS-96">McGrattan et al. (2026), pp. 96–97.</ref><ref name="FDS-135">McGrattan et al. (2026), pp. 135–136.</ref> Alternatively, a spread-rate model replaces these details with an empirical spread rate, which greatly reduces the complexity of the model.<ref name="FDS-135" /> By default, this model uses the formulae of Rothermel. The spread rate without wind or slope is then the ratio between the energy reaching the unburnt fuel and the energy needed to ignite it, both expressed through properties of the fuel bed.<ref name="FDS-137">McGrattan et al. (2026), p. 137.</ref>

FDS offers the 13 fuel models of Rothermel and Albini, and factors for wind and slope increase the spread rate at the head of the fire. The original Rothermel model counts wind and slope only when they point in the direction of spread, whereas FDS also handles wind and slope that point in different directions.<ref name="FDS-137" /> The fire front grows as a set of ellipses with a head, flanks and a back that spread at different rates. The ellipses are stretched in the direction set by the wind and the slope, and their ratio of length to breadth is limited to between 1 and 8.<ref name="FDS-135" /> By default, the wind is taken from a standard weather station measurement at 6.1 m above the ground and converted to mid-flame height.<ref name="FDS-138">McGrattan et al. (2026), p. 138.</ref>

In FDS, the time a patch of vegetation burns is assumed to depend mainly on the ratio of surface to volume of its fuel particles.<ref name="FDS-140">McGrattan et al. (2026), p. 140.</ref> In the particle approach, vegetation is described by this surface-to-volume ratio, its packing ratio and an assumed shape. How strongly it absorbs radiation is measured from the share of sunlight that passes through it, like the fraction of blue sky seen through a tree canopy.<ref name="FDS-96" /> In a coupled mode, the burning vegetation releases fuel gas that burns in the model, and the resulting plume interacts with the surrounding air.<ref name="FDS-139">McGrattan et al. (2026), p. 139.</ref>

Such predictions are only as good as their input, because a fire model predicts fire effects from data chosen by the user. Its estimates are technically credible only when the conditions for which the model was developed are not violated. Model outputs are single values that do not show the uncertainty in the inputs.<ref name="Notarianni">Notarianni (2002), p. 5-43.</ref>

== Suppression ==

One of the glossary definitions quoted in NUREG-1805 describes fire suppression as all the work of confining and extinguishing wildland fires.<ref name="NUREG-F" /> In the United States, wildfire control has its own NFPA standards. Examples listed in NUREG-1805 are NFPA 295, Standard for Wildfire Control (1998 edition), and NFPA 1051 on the professional qualifications of wildland fire fighters (2002 edition). Others cover wildland fire apparatus (NFPA 1906, 2001 edition) and protective clothing and equipment for wildland fire fighting (NFPA 1977, 1998 edition).<ref name="NUREG-E">Iqbal and Salley (2004), pp. E-6, E-10, E-12.</ref> Putting out the flames is not always the end, because smouldering in the duff layer can re-ignite a flaming fire.<ref name="Ohlemiller" />

Class A foams, intended for ordinary combustibles such as wood,<ref name="NUREG-B58">Iqbal and Salley (2004), pp. B-58–B-59.</ref> have been used widely in wildland fire suppression.<ref name="Scheffey">Scheffey and Hickey (2002), p. 4-144.</ref> Their success with fires in natural cover fuels led to research on their use in buildings.<ref name="Scheffey" /> In wildland use they are generally mixed with water at 0.1 to 1.0 per cent and applied with compressed air foam systems through hose lines.<ref name="NUREG-B60">Iqbal and Salley (2004), p. B-60.</ref> Foam keeps air away from the fire, produces steam, penetrates crevices and protects exposed material that is not yet burning. It is, however, unstable. Physical or mechanical forces break it down, heat drives out its water, and turbulent air can blow light foam away from the burning area.<ref name="NUREG-B58" />

== See also ==

* [[Facade fire]]
* [[Warehouse fire]]
* [[Car park fire]]

== Notes ==

<references />

== References ==

* Cox, G., & Kumar, S. (2002). Modeling enclosure fires using CFD. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-194–3-218). National Fire Protection Association; Society of Fire Protection Engineers.
* Hamins, A., Maranghides, A., McGrattan, K. B., Ohlemiller, T. J., & Anleitner, R. L. (2005). ''Experiments and modeling of multiple workstations burning in a compartment'' (NIST NCSTAR 1-5E). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Kanury, A. M. (2002a). Flaming ignition of solid fuels. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-229–2-245). National Fire Protection Association; Society of Fire Protection Engineers.
* McGrattan, K., Hostikka, S., Floyd, J., McDermott, R., Vanella, M., Mueller, E., & Paul, C. (2026). ''Fire Dynamics Simulator technical reference guide: Vol. 1. Mathematical model'' (6th ed., NIST Special Publication 1018-1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.1018
* Najafi, B., Joglar, F., & Dreisbach, J. (2007). ''Verification and validation of selected fire models for nuclear power plant applications: Vol. 1. Main report'' (NUREG-1824; EPRI 1011999). U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research; Electric Power Research Institute.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-200–2-210). National Fire Protection Association; Society of Fire Protection Engineers.
* Quintiere, J. G. (2002b). Surface flame spread. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-246–2-257). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L., & Hickey, H. E. (2002). Foam system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-123–4-148). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Special Hazards & Building Types]]

Lithium-ion battery fire

2026-11-02T18:32:41Z

Mark: Revise against the FSE wiki writing guidelines: corrections after independent fact-check (revised by Claude Opus 5.5)

A '''lithium-ion battery fire''' is a fire in a lithium-ion battery or battery pack that is driven by [[thermal runaway]]. Thermal runaway is a failure mechanism in which a battery cell heats itself up, and it can result in fire.<ref name="NIPV-22">Van der Graaf et al. (2021/2023), p. 22.</ref> Many electric cars store their energy in lithium-ion packs, which can hold 100 kWh or more.<ref name="NIPV-21">Van der Graaf et al. (2021/2023), p. 21.</ref> Once thermal runaway has started, heat can pass from cell to cell, flammable gases may be released and the fire keeps re-igniting until the energy in the pack is used up. The pack is sealed against moisture and dirt, so water cannot reach the cells directly and cooling needs a lot of water for a long time.<ref name="NIPV-22" />

In tests, burning electric cars reached temperatures and peak heat release rates similar to those of petrol and diesel cars.<ref name="NIPV-23">Van der Graaf et al. (2021/2023), p. 23.</ref><ref name="NIPV-25">Van der Graaf et al. (2021/2023), pp. 24–25.</ref> Their fires nevertheless develop more slowly, last longer, can involve repeated small explosions and flash fires, and release more hydrogen fluoride, a toxic and corrosive gas.<ref name="NIPV-29">Van der Graaf et al. (2021/2023), p. 29.</ref><ref name="NIPV-30">Van der Graaf et al. (2021/2023), p. 30.</ref> Together with high voltages, these risks are one reason why firefighting in indoor car parks may be limited or impossible.<ref name="NIPV-11">Van der Graaf et al. (2021/2023), p. 11.</ref> A 2021 study by the Netherlands Institute for Public Safety (NIPV) on indoor car parks with electric vehicles found that the probability of such fires could hardly be determined from empirical data.<ref name="NIPV-20">Van der Graaf et al. (2021/2023), p. 20.</ref>

== How thermal runaway starts ==

A battery pack in an electric car consists of cells of about 4 V, joined into modules of up to 60 V that together form a pack of 300 to 1,000 V.<ref name="NIPV-21" /> The SFPE Handbook explains the general principle of self-heating: heat produced by a chemical reaction competes with heat lost to the surroundings. Most reaction rates rise almost exponentially with temperature, but heat losses by conduction rise only linearly. Ignition, or thermal runaway, therefore begins where the temperature is highest, if it occurs at all.<ref name="Gray">Gray (2002), pp. 2-211–2-212.</ref>

In a battery, each pack has its own safety window, and beyond it the pack can heat up further and go into thermal runaway.<ref name="NIPV-22" /> The temperature at which this can start depends on the type of battery: the NIPV report gives 70 to 250 °C in one place and 50 to 270 °C in another.<ref name="NIPV-22" /><ref name="NIPV-18">Van der Graaf et al. (2021/2023), p. 18.</ref> Every electric car has a battery management system that monitors the individual cells.<ref name="NIPV-22" /> When limits are exceeded, it can switch on active cooling during charging, stop charging or disconnect the pack. The system is designed to be fail-safe, so a fault in the system itself also switches the pack off.<ref name="NIPV-23" />

A battery can fail because of a design or manufacturing error in the electrode, separator or electrolyte. This can lead to failures in the battery management system and to overcharging, but such errors are rare and, once detected, generally lead to a recall.<ref name="NIPV-23" /> Outside causes include external heat, misuse and damage in a collision.<ref name="NIPV-23" /> Parking and charging electric cars in car parks add causes that do not exist with petrol and diesel cars. Examples are a damaged cable or charging station, a fault in the battery management system, a collision with a charging station and a defective pack that has gone unnoticed.<ref name="NIPV-29" /> Radiant heat from a neighbouring burning car may also cause thermal runaway in an electric car parked next to it.<ref name="NIPV-32">Van der Graaf et al. (2021/2023), pp. 32–33.</ref>

How often batteries fail is uncertain. Estimates quoted in the NIPV report range from one failure in a million or fewer to about one in 100 million. The report concludes that the probability of battery failure seems relatively low. Still, no lithium-ion battery is intrinsically safe: no pack design can completely prevent the release of enough energy for thermal runaway.<ref name="NIPV-23" />

== Gases, chain reactions and explosions ==

A heating cell can release flammable gases. These may ignite if there is enough oxygen and the ignition temperature is reached, and the casing of the cell may be hot enough for this. The heat of one cell can also push the cells next to it into thermal runaway, so that the failure spreads through the pack as a chain reaction.<ref name="NIPV-22" /> Gases held in a pouch or cartridge can escape if the pack or its pressure valve fails under high pressure. If the pack is mechanically damaged, the pressure wave can throw out parts and fragments, which may be burning.<ref name="NIPV-22" />

Gas that does not ignite at once can build up into an explosive mixture in a confined or poorly ventilated space.<ref name="NIPV-27">Van der Graaf et al. (2021/2023), p. 27.</ref> If the mixture reaches its lower explosion limit, the lowest concentration at which a flame can spread through it, and is then ignited, a gas explosion can occur.<ref name="NIPV-27" /><ref name="NUREG-16">Iqbal and Salley (2004), p. 16-2.</ref> Among the gases that burning packs give off are hydrogen, methane and carbon monoxide.<ref name="NIPV-26">Van der Graaf et al. (2021/2023), p. 26.</ref> Hydrogen alone has a lower flammability limit in air of 4.1 per cent by volume, and its flame is often invisible in daylight.<ref name="NUREG-16" /> The NIPV report counts repeated small explosions, flying parts and flash fires among the ways in which fires in electric cars differ from other car fires.<ref name="NIPV-29" />
[[File:fse-lithium-ion-battery-fire-v1.svg|thumb|upright=1.5|alt=One hot cell heats neighbours, releasing gases that accumulate and can ignite or explode.|Thermal runaway can propagate and produce flammable gases. Based on Van der Graaf et al. (2021/2023), p. 22 and p. 27.]]

== Heat release and fire development ==

In terms of temperature, fires in electric cars do not differ significantly from those in conventional cars. Battery tests reviewed in the NIPV report measured maximum flame temperatures of 798 to 863 °C, rising with how fully the batteries were charged. Full-scale tests on both types of car measured 800 ± 100 °C.<ref name="NIPV-23" /> The heat radiation from an electric car with a fully charged pack was also similar to that from a conventional car.<ref name="NIPV-25" />

The heat release rate, the amount of heat a fire releases per second, largely determines how intense a fire is.<ref name="VR-4.5">Van Rossum (2027), §4.5.</ref> A review of published tests found similar peaks of about 6 MW for electric and fossil-fuelled cars. The total heat released was 4.7 to 8.5 GJ for electric cars and 3.3 to 10 GJ for the others.<ref name="NIPV-25" /> Larger batteries raise the peak: packs of about 15 to 25 kWh gave about 4 to 6 MW, while packs of more than 100 kWh give about 8 MW. That is significantly higher than the approximately 6.8 MW of an average mid-range conventional car.<ref name="NIPV-25" /> ''Introduction to Fire Safety Engineering'' gives a peak of 8.5 MW for a car and 2.5 MW for an average sofa.<ref name="VR-4.5" />

The course of the fire over time differs more. In a petrol or diesel car, the plastic tank can fail and suddenly release fuel that catches fire, so the temperature rises very rapidly in the first minutes. Battery cells first need time to warm up and give off gas. The temperature therefore rises evenly, at about 0.2 °C per minute, until thermal runaway makes it climb by more than 10 °C per minute.<ref name="NIPV-26" /> A normal passenger car fire generally burns for just over half an hour and peaks at about 5 MW after 10 to 15 minutes. An electric car left to burn without intervention burns out in about 90 minutes, and an extinguished one can keep re-igniting for several hours.<ref name="NIPV-26" />

An [[electric vehicle fire]] in a car park can spread from car to car as a travelling car fire. The NIPV report expects electric cars to make such fires more likely, because a long-burning pack radiates heat to its neighbours for longer.<ref name="NIPV-29" /> In 2021, Dutch building regulations, standards and guidelines were still based on fires in conventionally fuelled cars, and modern cars contain more plastic than older steel models.<ref name="NIPV-11" /> The car-fire curve in the Dutch standard NEN 6098 rests on a design fire set by TNO in 1999. In the TNO tests, fire could spread to the adjacent cars 10 to 15 minutes after the first one. With more plastics in modern cars, such curves may be less conservative in some situations.<ref name="VR-8.6">Van Rossum (2027), §8.6.</ref>

== Toxic and corrosive products ==

The toxic hazard of a fire, the subject of [[fire toxicity]], depends on how quickly and how much toxic products are produced, and on how potent they are.<ref name="Purser">Purser (2002), p. 2-91.</ref> Burning battery packs release corrosive substances from the electrolyte and combustion products from the plastics and packaging. Besides methane, carbon monoxide, carbon dioxide and hydrogen, they release the toxic gases hydrogen fluoride and hydrogen chloride.<ref name="NIPV-26" /> The SFPE Handbook counts these acid gases among the most important irritants in fire smoke. Irritants can impair escape or incapacitate people through pain and breathing difficulty.<ref name="Purser" />

A study cited in the NIPV report found about 20 to 200 mg of hydrogen fluoride per watt-hour of battery capacity. A 100 kWh pack can thus emit 2 to 20 kg, depending on its charge. Comparable tests on electric and conventional cars found hardly any difference in other toxic gases, but the electric cars appeared to produce about 1.8 times more hydrogen fluoride.<ref name="NIPV-26" /> Hydrogen fluoride binds to other substances and smoke particles and settles on floors, walls and ceilings. In one study this more than halved its concentration in the smoke within 10 to 20 minutes, but made firefighting clothing more contaminated.<ref name="NIPV-26" /> According to the report, a fire attack requires the clothing to be decontaminated because of the toxic and corrosive gases, unlike an attack on a conventional car fire.<ref name="NIPV-30" />
[[File:fse-lithium-ion-battery-fire-v2.svg|thumb|upright=1.5|alt=Battery smoke travels through air and deposits on clothing, walls, floors and residue.|Battery-fire contamination includes airborne and deposited hazards. Based on Van der Graaf et al. (2021/2023), pp. 26, 29–30, 39 and 47.]]

For people escaping, the extra hydrogen fluoride changes little. The plastic parts of any burning car already create severely toxic smoke, and the report puts the effect of the extra hydrogen fluoride on escape safety at zero. Systemic health effects seem unlikely, although slight exposure may irritate the skin and severe exposure may cause chemical burns.<ref name="NIPV-30" /> Research cited in the report found that firefighters in protective equipment can carry out a "safe" attack with proper hygiene if their exposure to the smoke lasts no more than 20 to 30 minutes.<ref name="NIPV-26" /> The report sees no reason to assume that they need more protective equipment than at a fire in a conventional car.<ref name="NIPV-47">Van der Graaf et al. (2021/2023), p. 47.</ref>

Smoke with extra hydrogen fluoride can spread from a car park through open doors into the escape routes and stairwells of buildings above.<ref name="NIPV-30" /> People who leave at once are exposed only briefly, but those who cannot escape or take longer are exposed for longer. For this reason the report advises against placing charging stations near pedestrian escape routes.<ref name="NIPV-39">Van der Graaf et al. (2021/2023), p. 39.</ref>

== Extinguishing and cooling ==

Fighting a battery fire involves two tasks: putting out the flames, and cooling the pack for a long time so that thermal runaway does not set it alight again. Putting out the flames needs no more capacity than for a conventional car.<ref name="NIPV-46">Van der Graaf et al. (2021/2023), p. 46.</ref> Stopping thermal runaway is much harder, because the closed construction of the pack keeps water away from the cells.<ref name="NIPV-22" /> According to the NIPV report, a burning pack can only be controlled by prolonged cooling with a lot of water, and extinguishing it requires water inside the pack.<ref name="NIPV-30" />

After the flames are out, the pack catches fire again within a short time. It therefore needs continuous cooling, and its temperature has to be monitored for a long time.<ref name="NIPV-46" /> Firefighters can extinguish continuously or each time the fire re-ignites, and the amount of water needed depends on the pack and how fully it is charged.<ref name="NIPV-46" /> For packs without special facilities, the most successful way to get water inside is to immerse the pack in water.<ref name="NIPV-30" /> An immersion container is currently the best method available for long-term cooling, but its effect depends on how far the water can reach the cells.<ref name="NIPV-46" />
[[File:fse-lithium-ion-battery-fire-v3.svg|thumb|upright=1.5|alt=Flames are knocked down before prolonged cooling, temperature monitoring and salvage.|Battery-fire response continues after visible flames disappear. Based on Van der Graaf et al. (2021/2023), pp. 45–47.]]

Fixed sprinkler or water mist systems cannot extinguish a fire in an electric car, because the water droplets cannot enter the pack. They can, however, reduce the probability that the fire grows and spreads to nearby structures and vehicles.<ref name="NIPV-37">Van der Graaf et al. (2021/2023), p. 37.</ref> Covering the car in foam is not a useful method for the time being. The fire can re-ignite under the foam, because packs in thermal runaway can re-ignite even when little oxygen is available.<ref name="NIPV-47" />

[[Fire classes]] sort fires by the type of fuel. In the US scheme of NFPA 10 (2002 edition), summarised in NUREG-1805, fires in energised electrical equipment form Class C, for which the agent must not conduct electricity.<ref name="NUREG-B">Iqbal and Salley (2004), p. B-13.</ref> The NIPV report, which deals with lithium-ion packs in cars, relies on water for cooling and extinguishing them.<ref name="NIPV-30" /> Although electric cars carry up to about 400 V, with peaks of up to 800 V, the probability of electrocution is negligible when the fire is fought from a distance.<ref name="NIPV-11" /><ref name="NIPV-43">Van der Graaf et al. (2021/2023), p. 43.</ref>

== Firefighting and salvage in car parks ==

In an indoor car park, a fire in an electric car adds several problems for the fire service. It is uncertain how the fire will develop and spread, and the pack can re-ignite and burn for longer. Explosions, flare fires and specific toxic gases can occur, and the deployment may be long and need a lot of water.<ref name="NIPV-43" /> The stability of the structure is uncertain, and a burning electric car may even start to move.<ref name="NIPV-30" /> The report concludes that the risks and uncertainties of an attack have increased compared with car parks without electric cars.<ref name="NIPV-43" />

Dutch fire services prefer to fight a fire from the outside. Before choosing an attack, they establish whether the location of the fire is known, whether it can be reached from outside and whether enough cooling capacity is available. Only if all three conditions are met can the fire be put out from the outside. Otherwise the attack becomes defensive, and a large structure such as a car park is in principle considered beyond saving.<ref name="NIPV-44">Van der Graaf et al. (2021/2023), p. 44.</ref> For car parks, the report concludes that an attack from inside is generally not safely possible, although the commanding officer may still decide on one.<ref name="NIPV-45">Van der Graaf et al. (2021/2023), p. 45.</ref> The fire service will not automatically enter, so a car park may burn out.<ref name="NIPV-47" />

Cooling capacity is estimated with rules of thumb. A high-pressure jet of 125 litres per minute is generally sufficient for a heat release rate of up to 2.5 MW. A low-pressure jet of 450 litres per minute generally suffices for up to 10 MW.<ref name="NIPV-45" /> Fires in electric cars call for low-pressure jets, and several burning cars will probably need several jets.<ref name="NIPV-44" /> ''Introduction to Fire Safety Engineering'' explains the idea behind such rules: the expected heat release rate of a fire indicates the cooling capacity needed to fight it.<ref name="VR-8.6" />

Because a pack can re-ignite after the fire is out, the report advises planning how an electric car can be removed from the car park. Together with a properly equipped salvage company, the fire service removes the car, which can then be left to react in a water tank until thermal runaway has stopped.<ref name="NIPV-42">Van der Graaf et al. (2021/2023), p. 42.</ref> Not every salvage company has the right equipment, and smoke or poor access can delay removal from an underground car park.<ref name="NIPV-46" /> In a fire in the Singelgarage car park in Alkmaar in 2020, the pack of one electric car kept re-igniting. A police robot towed the car out, and it was then cooled for a long time in an immersion container.<ref name="NIPV-12">Van der Graaf et al. (2021/2023), p. 12.</ref>

Ordinary extinguishing water from electric car fires harms the environment hardly more than that from other car fires and can go into the sewer.<ref name="NIPV-46" /> Cooling water in an immersion tank is different. Burnt packs contain lithium oxide, which reacts with water to form lithium hydroxide, so the pH of the water can keep rising.<ref name="NIPV-29" /> Such cooling water may not be discharged directly into the sewer, and a residue with a neutral pH on the outside may still contain heavy metals.<ref name="NIPV-47" />

== Prevention in car parks ==

In the Netherlands, the 2021 NIPV report discusses prevention against the Building Decree 2012, whose fire safety rules did not specifically address parking and charging electric cars.<ref name="NIPV-17">Van der Graaf et al. (2021/2023), p. 17.</ref> Under that decree, enclosed indoor car parks of more than 1,000 m² needed an automatic fire alarm system with full detection, and new indoor car parks had to have charging facilities.<ref name="NIPV-37" /><ref name="NIPV-10">Van der Graaf et al. (2021/2023), p. 10.</ref> Amendments proposed in 2021 for its successor, the Building Works and Living Environment Decree, would make sprinklers mandatory in certain car parks. They would also require a facility to switch off all charging points at once.<ref name="NIPV-18" />

The report offers its measures as a range from which to build a tailor-made set, not as a detailed standard.<ref name="NIPV-34">Van der Graaf et al. (2021/2023), p. 34.</ref> It sees a sprinkler or water mist system as the most obvious way to hold a fire to a few cars and so prevent a travelling fire.<ref name="NIPV-36">Van der Graaf et al. (2021/2023), p. 36.</ref><ref name="NIPV-49">Van der Graaf et al. (2021/2023), pp. 49–50.</ref> Fast detection helps, but its effect depends on prompt follow-up of the alarm.<ref name="NIPV-37" /><ref name="NIPV-40">Van der Graaf et al. (2021/2023), p. 40.</ref> Carbon monoxide detectors gave the fastest alert in one study, but in the Netherlands they are not used as fire detection.<ref name="NIPV-37" /> Collision protection for charging stations is a further measure.<ref name="NIPV-36" />

The report prefers parking spaces for electric cars near the vehicle entrances and at street level, so that a fire can be fought from outside and a car removed quickly.<ref name="NIPV-41">Van der Graaf et al. (2021/2023), pp. 41–42.</ref> It advises against places where ventilation air is supplied.<ref name="NIPV-39" /> Grouping charging points in one marked area helps the fire service find electric cars, but such clustering can also lead to a travelling car fire.<ref name="NIPV-42" /> Users can be told not to park a car whose battery management system reports a fault and to keep their distance if gases are released.<ref name="NIPV-40" />

== Uncertainties and limits ==

How often electric cars catch fire is largely unknown, because there are no reliable datasets.<ref name="NIPV-54">Van der Graaf et al. (2021/2023), p. 54.</ref> The report judges that a parked electric car is unlikely to catch fire more often than a fossil-fuelled car. Charging, however, is expected to raise the probability, because it adds an activity, the technology is still in its teething phase and existing electrical installations may not be safe enough.<ref name="NIPV-28">Van der Graaf et al. (2021/2023), p. 28.</ref> Ageing probably raises the internal resistance of the cells, which increases the heat they produce. An older battery also holds a lower maximum charge, however, so its thermal runaway is less intense and releases fewer flammable gases.<ref name="NIPV-28" />

The NIPV report covers only lithium-ion passenger cars in Dutch indoor car parks, and "lithium-ion" itself covers many kinds of lithium batteries that respond differently to fire.<ref name="NIPV-18" /> It warns that test results vary greatly with the amount of fuel, the battery capacity and the plastics in the car, so single studies cannot simply be generalised.<ref name="NIPV-20" /> Battery packs can also be combined into systems of 10 to 400 kWh, for example in trucks and electric ships. Stationary installations such as a [[battery energy storage system]] lie outside the report's scope.<ref name="NIPV-21" /><ref name="NIPV-18" /> Open questions include the exact process of thermal runaway, the conditions under which packs re-ignite and the best detection and suppression systems.<ref name="NIPV-55">Van der Graaf et al. (2021/2023), p. 55.</ref>

== See also ==

* [[Car park fire]]
* [[Tunnel fire]]
* [[Warehouse fire]]

== Notes ==

<references />

== References ==

* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-211–2-228). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-83–2-171). National Fire Protection Association; Society of Fire Protection Engineers.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Special Hazards & Building Types]]

Vegetation fire

2026-11-02T18:11:33Z

Mark: Redirect to Wildfire (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Wildfire]]

Wild fire

2026-11-02T18:11:26Z

Mark: Redirect to Wildfire (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Wildfire]]

Forest fire

2026-11-02T18:11:20Z

Mark: Redirect to Wildfire (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Wildfire]]

Fire investigation

2026-11-02T18:11:14Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, new sourced content, See also, links, style (revised by Claude Opus 5.5)

'''Fire investigation''' is the examination of a fire after the event to establish where and how it started, how it developed and how the building, its fire protection and its occupants were affected. Writing on spontaneous ignition in the SFPE Handbook, Gray notes that fire prevention and fire cause investigation both need to identify the critical conditions for ignition, before and after the event respectively.<ref name="Gray-2-211">Gray (2002), p. 2-211.</ref> Hall and Ahrens list the reconstruction of major fires among the engineering analyses that require input data on fires.<ref name="HA-5-65">Hall and Ahrens (2002), p. 5-65.</ref> The Society of Fire Protection Engineers likewise counts post-fire investigation and analysis as part of fire protection engineering.<ref name="IFEG-US-0.3-1">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-1–0.3-2.</ref>

Fire investigation matters because its findings explain why fires start and why protection succeeds or fails, and they can lead to changes in how buildings are designed, built and regulated. The US investigation of the World Trade Center disaster of 2001, for example, was meant to serve as the basis for improvements in building practice and revisions to codes and standards.<ref name="NIST-xxxv">National Institute of Standards and Technology (2005), p. xxxv.</ref> Investigations depend on the evidence that survives, and large fires destroy much of it. Fire loss statistics from many sources show an unknown cause more often in fires with multimillion-dollar losses than in smaller fires, probably because more evidence is lost.<ref name="Gray-2-211" />

== Purpose and scope ==

Investigations differ in purpose and authority. The US National Institute of Standards and Technology (NIST) investigated the World Trade Center disaster to determine why and how the buildings collapsed. It also asked why injuries and fatalities were high or low depending on location, and examined the procedures used in design, construction, operation and maintenance and the parts of codes and standards that warranted revision.<ref name="NIST-xxxv" /> NIST is a non-regulatory agency whose investigations focus on fact finding. It has no authority to find fault or negligence, and its reports may not be used in lawsuits for damages.<ref name="NIST-xxxv" />

Other investigations can have legal consequences. Van Rossum notes that an investigation after a fire disaster may show that the cause lies in demonstrably wrong advice, below the knowledge and skill that could be expected at the time. In that case the adviser can be prosecuted.<ref name="VR-2.5">Van Rossum (2027), §2.5.</ref>

Fire services also investigate routine fires. For the World Trade Center buildings, the New York City fire department provided NIST with 112 records of its Bureau of Fire Investigation from 1977 to 2001. It also provided 397 operational fire reports from 1970 to 2001, all on standardised forms. NIST's review of earlier fires included, for example, a fire on 14 February 1975 on the 11th floor of WTC 1, one of the two towers. It spread through unprotected floor openings in utility closets and caused damage from the 10th to the 19th floor.<ref name="Kuligowski-1">Kuligowski et al. (2005), p. 1.</ref>

Large investigations break the work into specific questions. For the sprinklers, standpipes and hoses of the towers, the NIST study first documented their design and installation and compared them with the codes and standards of record. It then estimated their capacity under normal conditions with hydraulic calculations.<ref name="Hopkins-xxxii">Hopkins et al. (2005), p. xxxii.</ref> Only then did it ask what happened to the systems at each major event, how their performance was affected and at what point in the sequence they were lost.<ref name="Hopkins-xliii">Hopkins et al. (2005), p. xliii.</ref>
[[File:fse-fire-investigation-v1.svg|thumb|upright=1.5|alt=Questions guide evidence collection, reconstruction, modelling and findings with uncertainty.|Fire investigation reconstructs events from evidence and explicit inference. Based on Hopkins, Schoenrock, and Budnick (2005), pp. xxxi–xxxii and Hall and Ahrens (2002), pp. 5-65–5-67.]]

== Evidence and how it is gathered ==

Fire investigators normally read the path and intensity of a fire from telltale signs left in the building. In the World Trade Center towers this was impossible because neither building remained, so NIST relied on what may have been the most photographed disaster in history.<ref name="Gann-xxxviii">Gann, Hamins, et al. (2005), p. xxxviii.</ref> In each photograph and video frame, every window was coded for fire, smoke and whether the window was still in place, which produced detailed timelines of fire spread.<ref name="Gann-xxxviii" /> NIST also reviewed tens of thousands of pages of documents, interviewed over a thousand people and analysed 236 pieces of steel recovered from the wreckage.<ref name="NIST-xxxvi">National Institute of Standards and Technology (2005), p. xxxvi.</ref>

Time links the evidence together. NIST describes time as the unifying factor in combining photographs, videos, survivor accounts, emergency calls and communications among emergency responders.<ref name="NIST-82">National Institute of Standards and Technology (2005), p. 82.</ref> Images were timed by matching them to one well-defined event, the impact of the second aircraft at 9:02:59 a.m., and then to other events visible in several images. In all, 3,032 photographs and 2,673 video clips were timed to within 3 seconds or better, and the uncertainty of each time was logged.<ref name="NIST-83">National Institute of Standards and Technology (2005), pp. 83–84.</ref>

Physical evidence needs careful interpretation. NIST found that the primer paint on the towers' steel cracked in a "mud cracking" pattern above 250 °C. Deformation and the environment can also cause such cracks, so their absence shows that the steel stayed below 250 °C, but their presence does not prove high temperature.<ref name="Gayle-94">Gayle et al. (2005), p. 94.</ref> The method could not tell whether the heating happened before or after the collapse. The panels examined were also only 3% of the perimeter columns on the fire floors and could not be treated as representative of the others.<ref name="Gayle-xli">Gayle et al. (2005), p. xli.</ref>

People are a source of evidence as well. For the evacuation of the towers, NIST gathered over 1,000 new interviews with survivors, over 700 published interviews, emergency calls and transcripts of emergency communications.<ref name="Averill-iii">Averill et al. (2005), p. iii.</ref> Proulx notes that fire victims may have difficulty reporting accurately how long they waited before starting to evacuate, but that interview techniques can give acceptable estimates.<ref name="Proulx-3-349">Proulx (2002), p. 3-349.</ref> The causes of death in fires have been studied through pathological investigations of fire victims.<ref name="Purser-2-85">Purser (2002), p. 2-85.</ref> Carbon monoxide combines with haemoglobin in the blood to form carboxyhaemoglobin. In the Strathclyde study of fire deaths in the United Kingdom, 54% of those who died had a lethal level of it, and 69% had a level capable of causing incapacitation.<ref name="Purser-2-100">Purser (2002), p. 2-100.</ref>

== Establishing the cause ==

To describe how a fire started, investigators separate the parts of the ignition sequence. US fire incident coding distinguishes the form of heat of ignition and the equipment involved, which together describe the [[ignition source]], from the form and type of material first ignited. It also records the ignition factor that brought heat and fuel together, and the area of origin.<ref name="HA-5-68">Hall and Ahrens (2002), p. 5-68.</ref> The New York fire department's structural fire form recorded the same kind of information, and it called the ignition factor the cause.<ref name="Kuligowski-2">Kuligowski et al. (2005), p. 2.</ref>

Some causes leave characteristic traces. Spontaneous ignition of stacked material, such as cotton, woodchips or oily rags, starts in the well-insulated centre of the pile. Such a pile can therefore be charred or burnt to ash inside while looking almost untouched outside.<ref name="Gray-2-212">Gray (2002), p. 2-212.</ref><ref name="Gray-2-224">Gray (2002), p. 2-224.</ref> Hot gases escape along the path of least resistance and form "chimneys" of charred material, and several chimneys are the norm. Gray reports that finding more than one heavily charred area has led to wrongful charges of arson, based on the myth that more than one seat of fire means the fire was started deliberately.<ref name="Gray-2-225">Gray (2002), p. 2-225.</ref>

Gray lists the practical factors that make spontaneous ignition more likely, including a large body of material, high surrounding temperatures, thermal insulation, porous or fibrous material and a high stacking temperature.<ref name="Gray-2-224" /> Material left undisturbed for longer than usual is also reason for suspicion. In one case a warehouse of cottonseed meal burned down after a transport strike had left the meal in place far longer than normal.<ref name="Gray-2-225" /> In another, an instant-noodle factory burned down after new management sped up the production line, so that the noodles were packed hotter than before. Laboratory tests and calculations then showed that the packed pallets could ignite spontaneously at the new temperatures but not at the old ones.<ref name="Gray-2-226">Gray (2002), pp. 2-225–2-226.</ref>

Gray advises caution about the timing of such fires without detailed knowledge of the initial conditions.<ref name="Gray-2-224" /> Whenever spontaneous ignition is suspected, Gray recommends excavating the material, with photographs and temperature probe records at all stages. He has measured temperatures as high as 200 °C in buried material more than two weeks after a fire was put out. Unburnt oily rags at the bottom of a bin do not rule out spontaneous ignition either.<ref name="Gray-2-225" />

== Reconstructing the fire ==

A reconstruction places the evidence in the sequence of the fire. Van Rossum divides a room fire into three phases. In the development phase, a local fire of one or a few objects grows until flashover. After flashover the fire is fully developed, and the decay phase can begin, for example, when the fuel runs out or the fire brigade intervenes. These [[fire development stages]] matter for interpretation, because an active suppression system normally acts during the development phase and so prevents the fire from becoming fully developed.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>

[[Fire dynamics]], defined in a US nuclear regulatory report as the scientific study of hostile fires, describes ignition, flame spread, fire growth, smoke movement and their effects in an enclosure.<ref name="Iqbal-1-1">Iqbal and Salley (2004), p. 1-1.</ref> Smoke rises under buoyancy to the upper part of the room of origin and leaves through openings, driven mainly by pressure differences. The International Fire Engineering Guidelines (2005 edition) note that hand calculations of its spread beyond the room of origin are more difficult and more uncertain than those within it.<ref name="IFEG-2.5-2">National Research Council of Canada et al. (2005), p. 2.5-2.</ref><ref name="IFEG-2.5-6">National Research Council of Canada et al. (2005), p. 2.5-6.</ref>

Tests can fill gaps in the evidence. NIST set out to characterise the type, mass and layout of the combustibles in the towers, the fire endurance of the partitions and the properties of the insulation on the steel.<ref name="Gann-2">Gann, Hamins, et al. (2005), p. 2.</ref> Its reconstruction relied heavily on computer simulation, because the premises could not be examined after the fire and eyewitness information was severely limited. To support the simulations, NIST burned six single office workstations, the dominant combustibles in the buildings, to learn how they may have burned and to improve its fire model.<ref name="Ohlemiller-iii">Ohlemiller et al. (2005), p. iii.</ref>

== Modelling and computational fluid dynamics ==

[[Computational fluid dynamics]] (CFD) studies the flow of gases and liquids by solving the flow equations numerically on a grid of cells. A CFD model can show smoke spread, gas temperatures and velocities, flows through openings and the time to flashover in three dimensions as they change over time.<ref name="VR-11.1">Van Rossum (2027), §11.1.</ref><ref name="VR-11.2">Van Rossum (2027), §11.2.</ref> Turbulent flows, which are typical of fires, can only be approximated. CFD therefore gives good qualitative insight, but its exact results must be interpreted carefully and critically.<ref name="VR-11.1" /> Zone models such as CFAST, released by NIST,<ref name="VR-9.5">Van Rossum (2027), §9.5.</ref> are also used internationally for fire safety design and post-fire reconstruction.<ref name="Peacock-3">Peacock et al. (2026), p. 3.</ref>

In the World Trade Center investigation, the unusual mix of available information led to a high reliance on computational tools, and NIST upgraded its CFD model, the Fire Dynamics Simulator, for the reconstruction.<ref name="Gann-2" /><ref name="Gann-4">Gann, Hamins, et al. (2005), p. 4.</ref> It varied the uncertain inputs to find those to which the results were most sensitive and those that agreed best with the photographs.<ref name="Gann-2-3">Gann, Hamins, et al. (2005), pp. 2–3.</ref> The accuracy of the predictions was judged by their consistency with the photographic evidence.<ref name="Gann-4" /> For each tower it ran a less severe and a more severe case, which gave some understanding of the uncertainty in the predictions.<ref name="NIST-81">National Institute of Standards and Technology (2005), pp. 81–82.</ref>
[[File:fse-fire-investigation-v3.svg|thumb|upright=1.5|alt=Two candidate scenarios are tested against observations and model limitations before conclusions.|Alternative reconstructions should be tested against evidence and sensitivity. Based on Notarianni (2002), pp. 5-43–5-44 and McGrattan et al. (2026), p. 107.]]

Models also have limits. NIST decided not to model smoke movement and survival conditions throughout the occupied parts of the towers. There was no quantitative information on conditions inside the towers and no verifiable information on damage between floors, so such simulations for the impact floors and above would have been grossly uncertain.<ref name="Gann-3">Gann, Hamins, et al. (2005), p. 3.</ref>

The Fire Dynamics Simulator predicts the thermal environment of a fire, but it relies on empirical models for the activation of sprinklers and detectors.<ref name="FDS-107">McGrattan et al. (2026), p. 107.</ref> Smoke detector response is especially hard to model, because the production and transport of smoke early in a fire are not well understood.<ref name="FDS-108">McGrattan et al. (2026), p. 108.</ref> Notarianni adds that fire model outputs are single values that do not reflect the uncertainty in inputs such as fire growth rates. A predicted activation time of 121 s for a detector, for example, may in reality be longer or shorter, depending on uncertain inputs and on factors the model does not include.<ref name="Notarianni-5-43">Notarianni (2002), p. 5-43.</ref> In forensic reconstructions, the amount of soot deposited on surfaces in a simulation can be correlated with what is observed after the fire.<ref name="FDS-87">McGrattan et al. (2026), p. 87.</ref>

== Evaluating protection systems ==

An investigation compares what a system could do with what it actually did. NIST found that the sprinkler and standpipe systems of the towers had for the most part exceeded the code requirements of their time, but the adverse effects of the aircraft impacts on them were extensive.<ref name="Hopkins-xlv">Hopkins et al. (2005), p. xlv.</ref> WTC 1 was the first tower to be struck.<ref name="Hopkins-xxxi">Hopkins et al. (2005), p. xxxi.</ref> Its estimated impact damage would probably have destroyed at least one standpipe riser and the sprinkler systems on the 94th to 96th floors, and cut the water supply to other systems after a limited time.<ref name="Hopkins-xliii" /><ref name="Hopkins-xliv">Hopkins et al. (2005), p. xliv.</ref> The collapse of WTC 2 damaged the city water mains near the site, and the collapse of WTC 1 probably caused significant further damage.<ref name="Hopkins-xliv" />
[[File:fse-fire-investigation-v2.svg|thumb|upright=1.5|alt=Pre-incident conditions, ignition, detection, fire growth and consequences, with fire, water-supply and occupant tracks.|An investigation must align system states with the incident timeline. Based on Hopkins, Schoenrock, and Budnick (2005), pp. xxxi–xlii and Van Rossum (2027), §4.11.]]

The evidence on systems is often incomplete. For the towers' suppression systems there was very little eyewitness or communications information. NIST therefore based its estimates on the incident information it had gathered, the likely effects of the impacts and historical performance records for sprinklers.<ref name="Hopkins-xxxi" /> Most of the New York fire department's reports of significant earlier fires documented the performance of detectors and sprinklers, but almost all lacked information on the smoke purge system.<ref name="Kuligowski-2" />

Which sprinklers opened, and when, also needs careful reading. Water droplets carried by the hot gas flow under the ceiling from the first sprinklers can cool the heat-sensitive links of sprinklers further away and delay their opening. Cooper calls this random effect sprinkler skipping, and fusible-link vents can be delayed in the same way.<ref name="Cooper-3-239">Cooper (2002b), p. 3-239.</ref> Evidence from victims has comparable limits. Carboxyhaemoglobin is routinely measured in the blood of fire victims, but blood cyanide often is not, and post-fire cyanide levels are hard to relate to the exposure during the fire.<ref name="Purser-2-100" /><ref name="Purser-2-103">Purser (2002), p. 2-103.</ref>

== Limits and use of findings ==

Investigators often work with fragmented information. NIST confirmed significant events from more than one source where possible, but this could not always be done, and it included events that it judged likely or probable from the accumulated information.<ref name="Hopkins-xxxi" /> Records can also be lost. The Port Authority of New York and New Jersey kept records of all significant fire events in the World Trade Center buildings, and these were lost in the collapse of the towers.<ref name="Kuligowski-1" /> Physical evidence may cover only a small and unrepresentative part of a building, as the recovered steel did.<ref name="Gayle-xli" />

A single investigation describes one event. Hall and Ahrens note that detailed accounts, including NFPA's reports of fire investigations, show the range and diversity of fires that can happen. Such anecdotes cannot be used to estimate incident rates or probabilities.<ref name="HA-5-70">Hall and Ahrens (2002), p. 5-70.</ref> Valid analysis of incident rates instead requires a statistically representative database of [[fire statistics]].<ref name="HA-5-69">Hall and Ahrens (2002), p. 5-69.</ref>

Collected investigation data can in turn feed design values. Holborn and colleagues analysed data from fire investigations in the Greater London area between 1996 and 2000 to derive fire sizes, fire growth rates and the times between events. The Australian data sheets for the Fire Safety Verification Method (print version 1.1, 2020) use their results for characteristic fire growth rates and for the share of fires that become fully developed.<ref name="Holborn-2004">Holborn et al. (2004), as cited in Australian Building Codes Board (2020a), Data Sheet B2, pp. 4–7.</ref> The World Trade Center investigation itself ended with 30 recommendations, covering structural integrity, fire endurance, active fire protection, evacuation, emergency response, procedures and practices, and education and training.<ref name="NIST-xiii">National Institute of Standards and Technology (2005), p. xiii.</ref>

== See also ==

* [[Firefighting]]
* [[Dry and wet risers]]
* [[Fire hydrant]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Averill, J. D., Mileti, D. S., Peacock, R. D., Kuligowski, E. D., Groner, N., Proulx, G., Reneke, P. A., & Nelson, H. E. (2005). ''Occupant behavior, egress, and emergency communications'' (NIST NCSTAR 1-7). National Institute of Standards and Technology.
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Gann, R. G., Hamins, A., McGrattan, K. B., Mulholland, G. W., Nelson, H. E., Ohlemiller, T. J., Pitts, W. M., & Prasad, K. R. (2005). ''Reconstruction of the fires in the World Trade Center towers'' (NIST NCSTAR 1-5). National Institute of Standards and Technology.
* Gayle, F. W., Fields, R. J., Luecke, W. E., Banovic, S. W., Foecke, T., McCowan, C. N., Siewert, T. A., & McColskey, J. D. (2005). ''Mechanical and metallurgical analysis of structural steel'' (NIST NCSTAR 1-3). National Institute of Standards and Technology.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-211–2-228). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Kuligowski, E. D., Evans, D. D., & Peacock, R. D. (2005). ''Post-construction fires prior to September 11, 2001'' (NIST NCSTAR 1-4A). National Institute of Standards and Technology.
* McGrattan, K., Hostikka, S., Floyd, J., McDermott, R., Vanella, M., Mueller, E., & Paul, C. (2026). ''Fire Dynamics Simulator technical reference guide: Vol. 1. Mathematical model'' (6th ed., NIST Special Publication 1018-1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.1018
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Ohlemiller, T. J., Mulholland, G. W., Maranghides, A., Filliben, J. J., & Gann, R. G. (2005). ''Fire tests of single office workstations'' (NIST NCSTAR 1-5C). National Institute of Standards and Technology.
* Peacock, R. D., McGrattan, K. B., Forney, G. P., & Reneke, P. A. (2026). ''CFAST – Consolidated Fire and Smoke Transport: Vol. 1. Technical reference guide'' (Version 7, NIST Technical Note 1889v1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.TN.1889v1
* Proulx, G. (2002). Movement of people: The evacuation timing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-342–3-366). National Fire Protection Association; Society of Fire Protection Engineers.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-83–2-171). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Bushfire

2026-11-02T18:11:08Z

Mark: Redirect to Wildfire (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Wildfire]]

Wildfire

2026-11-02T18:11:02Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, added sources, See also, links, style (revised by Claude Opus 5.5)

A '''wildfire''', also called a wildland fire or bushfire, is a fire that spreads through vegetation. It can burn the brush on a forest floor, the crowns of trees, or gorse and heather.<ref name="Q-255">Quintiere (2002b), p. 2-255.</ref><ref name="IFEG-5">National Research Council of Canada et al. (2005), p. 1.6-5.</ref> How it spreads depends on the type and arrangement of the fuel, the terrain, the wind and the humidity. The flames heat the vegetation ahead of them by radiation and convection, and the wind can carry burning embers far ahead to start new fires.<ref name="Q-255" /> Forest fires spread at rates of the order of 1 to 100 cm per second, or about 0.6 to 60 m per minute.<ref name="Q-247">Quintiere (2002b), p. 2-247.</ref>

For fire safety engineering, wildfires matter where vegetation borders buildings, because fire can reach a building through embers, radiation or direct flame contact.<ref name="IFEG-5" /><ref name="IFEG-7">National Research Council of Canada et al. (2005), p. 1.6-7.</ref> Their smoke can also affect infrastructure. A US fire risk method for nuclear power plants assumes that heavy smoke from a large forest fire will make high-voltage transmission equipment trip off-line.<ref name="Nowlen">Nowlen et al. (2005b), p. T-14.</ref> Fire risk analysis counts wildland fires among the natural catastrophes that make zero fire risk unattainable.<ref name="Watts">Watts and Hall (2002), p. 5-4.</ref> The SFPE Handbook does not describe wildfire research in detail and refers to practical methods for estimating spread in forests developed by the US Forest Service.<ref name="Q-255" />

== How a wildfire spreads ==

[[Flame spread]] is the movement of a flame that stays close to the solid or liquid fuel feeding it. In natural fires, it largely decides how the fire develops.<ref name="Q-246">Quintiere (2002b), p. 2-246.</ref> Fire spread over a fuel is often seen as a chain of ignitions, in which the flame heats and ignites the material just ahead of it.<ref name="Kanury">Kanury (2002a), p. 2-229.</ref> Growth is a race between spreading and burning. If the flame spreads quickly compared with the time the fuel needs to burn out, the fire is likely to accelerate.<ref name="Q-246" />

In a forest, the porous brush on the forest floor usually burns. In severe fires the crowns of the trees burn as well, or even on their own.<ref name="Q-255" /> Like most natural fires, a forest fire burns with diffusion flames, because no burner mixes the fuel and the air beforehand.<ref name="NUREG-3-12">Iqbal and Salley (2004), p. 3-12.</ref> Its advancing front is a long, narrow line of fire that draws in air from both sides as the hot gases rise, like a row of burning townhouses.<ref name="NUREG-9-2">Iqbal and Salley (2004), p. 9-2.</ref> A brush fire is an example of a fire whose energy output is small compared with its diameter, the opposite of an oil-well blowout fire, and most ordinary accidental fires lie in between.<ref name="Najafi">Najafi et al. (2007), p. 2-27.</ref>

The SFPE Handbook gives spread rates of the order of 1 to 100 cm per second for forest and urban fires, the same order as upward flame spread on thick solids. Flames creeping sideways or downwards over a thick solid move at about 0.1 cm per second, and smouldering at only 0.001 to 0.01 cm per second.<ref name="Q-247" /> For the same heating, flames spread faster over a fuel of lower density.<ref name="Q-247" /> An approximate correlation by Thomas, quoted for wildland fires, wood cribs and urban conflagrations, makes the spread rate rise with wind speed. The rate falls as the fuel bed becomes denser. The handbook also compares spread rates for wood cribs, gorse and heather, and urban fires in Japan at different wind speeds.<ref name="Q-255" />

== Wind, slope and radiation ==

Flame spread in a forest depends on radiant heat transfer and on convective heating caused by the wind or by the slope of the terrain.<ref name="Q-255" /> When the flow runs in the direction of spread, the flame and its hot gases heat a stretch of unburnt fuel about as long as the flame, 0.1 to 10 m. A flame spreading against the flow heats only 1 to 3 mm ahead of it. Such wind-aided spread can accelerate and therefore appears more rapid.<ref name="Q-250">Quintiere (2002b), pp. 2-250–2-251.</ref> A slope works in a similar way, and forest fires are known to accelerate uphill because their flames lean towards the slope. Analysis of the King's Cross underground fire in London showed the same effect: flames on a wooden escalator lay down in its trench instead of rising vertically.<ref name="Cox">Cox and Kumar (2002), p. 3-207.</ref>
[[File:fse-wildfire-v1.svg|thumb|upright=1.5|alt=Wind and slope tilt flames towards uphill vegetation while a fuel gap interrupts one path.|Wildfire spread depends on fuel, terrain and wind. Based on Quintiere (2002b), p. 2-255 and Cox and Kumar (2002), p. 3-207.]]

[[Flame radiation]] preheats the fuel ahead of the front, and as the fuel warms up through radiation and convection from the fire, the spread accelerates.<ref name="Q-247" /> Radiation dominates heat transfer at high temperatures, from about 400 °C, because its intensity rises with the fourth power of the temperature.<ref name="VR-5.4">Van Rossum (2027), §5.4.</ref> How much of it reaches a target depends on the [[view factor]]. This is larger for a bigger radiating surface and smaller at a greater distance or a more oblique angle. A radiating surface of only 5 m² can fill almost the whole view of a target close to it, while the sun is enormous but too far away to have a large view factor.<ref name="VR-5.4" /> Radiation also lets a fire cross gaps, and the jump of a forest fire across a firebreak is generally viewed as ignition by radiation.<ref name="Kanury" />

== Firebrands and fuel breaks ==

[[Firebrands]] are flaming or smouldering objects carried through the air from a fire, which can sometimes ignite combustibles far away. An ember is a particle of solid material that gives off radiant energy because of its temperature or because it is burning at its surface.<ref name="NUREG-F">Iqbal and Salley (2004), pp. F-17, F-22, F-24, F-29.</ref> In a forest fire, wind currents can carry large embers great distances and start spot fires at other locations.<ref name="Q-255" />

The brands are lifted by the rising hot gases of the fire and then fall onto combustible material. This mechanism has been observed in warehouse fires and wildland fires, both of which involve cellulosic materials. In NIST tests with burning office workstations, by contrast, there was no evidence that flying brands played a role. There the fire spread through burning carpet and through radiation from the hot smoke layer.<ref name="Hamins">Hamins, Maranghides, McGrattan, Ohlemiller, and Anleitner (2005), p. 30.</ref>
[[File:fse-wildfire-v2.svg|thumb|upright=1.5|alt=Wind carries burning brands over a fuel break to ignite a separate spot fire.|Firebrands create discontinuous spread beyond the main fire front. Based on Quintiere (2002b), p. 2-255 and Hamins, Maranghides, McGrattan, Ohlemiller, and Anleitner (2005), p. 30.]]

[[Fire spread]] through vegetation can be controlled with breaks in the fuel. The size of break needed to stop a fire depends on the size of the fire and on how it transfers heat.<ref name="Q-255" /> According to a glossary definition quoted in NUREG-1805, controlling a fire means completing a control line around it. The line also has to enclose any spot fire from it and any interior island to be saved. Unburnt areas next to the line on the fire side are also burnt out, and hot spots that threaten the line are cooled.<ref name="NUREG-F" />

Fire can also stay in the ground. The duff layer on a forest floor, a porous layer of decaying organic material, is often set smouldering by a passing forest fire.<ref name="Ohlemiller">Ohlemiller (2002), p. 2-206.</ref> This [[smouldering]] is very irregular in extent. It can re-ignite a flaming fire, and it also affects whether dormant seeds survive and the forest regenerates.<ref name="Ohlemiller" />

== Buildings at the wildland-urban interface ==

Where wildland borders built-up areas, at the [[wildland-urban interface]], a vegetation fire can reach buildings.<ref name="IFEG-5" /><ref name="FDS-ix">McGrattan et al. (2026), p. ix.</ref> The International Fire Engineering Guidelines (2005) list three routes for fire spread from a burning building to a neighbouring building or property boundary: burning embers and other debris, radiation, and direct flame contact.<ref name="IFEG-7" /> The same guidance notes that flying brands and embers may need to be considered if fire spread to adjoining property is to be limited. This may have design implications in areas prone to bushfires.<ref name="IFEG-5" /> For adjacent buildings, fire can even spread by radiation through the glass of closed windows without the glass breaking.<ref name="IFEG-7" />
[[File:fse-wildfire-v3.svg|thumb|upright=1.5|alt=Vegetation fire exposes a building by direct flames, radiant heat and firebrands.|Buildings at the wildland-urban interface face several ignition pathways. Based on National Research Council of Canada et al. (2005), p. 1.6-7 and Quintiere (2002b), p. 2-255.]]

Fire growth across separate combustibles, such as the buildings of a city, involves radiant heating to ignition.<ref name="Kanury" /> In New Zealand, the rules on [[fire spread between buildings]] are written in terms of radiation. Building Code clause C3.6, applied in C/VM2 (second edition, 2025), limits the radiation from a fire in a building. At the relevant property boundary it may not exceed 30 kW/m², and at 1 m beyond the boundary 16 kW/m². Under clause C3.7, external walls closer than 1 m to the boundary must be non-combustible or must resist ignition under 30 kW/m² for 15 or 30 minutes, depending on the importance level of the building.<ref name="CVM2">Ministry of Business, Innovation and Employment (2025b), p. 43.</ref> These criteria are written for a fully developed fire in a building that exposes a neighbouring building, not for burning vegetation.<ref name="CVM2" />

The design fire behind these rules assumes that the unprotected wall areas of a burning building emit 83 to 144 kW/m² without sprinklers and 58 to 101 kW/m² with them, depending on the fire load. C/VM2 also comments that this design fire assumes firefighters will be available after some time to prevent fire spread to neighbouring property.<ref name="CVM2-44">Ministry of Business, Innovation and Employment (2025b), p. 44.</ref> The commentary on the first edition of C/VM2 notes that ordinary timber cladding ignites in less than 15 minutes when exposed to 30 kW/m². Non-combustible materials can be assumed not to ignite up to that level. It adds that the design values do not guarantee that fire spread is prevented in every situation, partly because they assume timber cladding with a moisture content of 15 per cent. In New Zealand, fire spread to adjacent property occurred in about 3 per cent of all structure fires between 2005 and 2010.<ref name="Commentary">Ministry of Business, Innovation and Employment (2013), p. 23.</ref>

== Predicting wildfire spread ==

The Fire Dynamics Simulator (FDS), a computer fire model, includes a wildland fire spread model, and the US Forest Service supported the development of its sub-models for the wildland-urban interface.<ref name="FDS-ix" /> FDS can represent grasses, leaves and burning brands as particles, so that their heating and decomposition are calculated directly.<ref name="FDS-96">McGrattan et al. (2026), pp. 96–97.</ref><ref name="FDS-135">McGrattan et al. (2026), pp. 135–136.</ref> Alternatively, a spread-rate model replaces these details with an empirical spread rate, which greatly reduces the complexity of the model.<ref name="FDS-135" /> By default, this model uses the formulae of Rothermel. The spread rate without wind or slope is then the ratio between the energy reaching the unburnt fuel and the energy needed to ignite it, both expressed through properties of the fuel bed.<ref name="FDS-137">McGrattan et al. (2026), p. 137.</ref>

FDS offers the 13 fuel models of Rothermel and Albini, and factors for wind and slope increase the spread rate at the head of the fire. The original Rothermel model counts wind and slope only when they point in the direction of spread, whereas FDS also handles wind and slope that point in different directions.<ref name="FDS-137" /> The fire front grows as a set of ellipses with a head, flanks and a back that spread at different rates. The ellipses are stretched in the direction set by the wind and the slope, and their ratio of length to breadth is limited to between 1 and 8.<ref name="FDS-135" /> The wind is taken from a standard weather station measurement at 6.1 m above the ground and converted to mid-flame height.<ref name="FDS-138">McGrattan et al. (2026), p. 138.</ref>

In FDS, the time a patch of vegetation burns is assumed to depend mainly on the ratio of surface to volume of its fuel particles.<ref name="FDS-140">McGrattan et al. (2026), p. 140.</ref> In the particle approach, vegetation is described by this surface-to-volume ratio, its packing ratio and an assumed shape. How strongly it absorbs radiation is measured from the share of sunlight that passes through it, like the fraction of blue sky seen through a tree canopy.<ref name="FDS-96" /> In a coupled mode, the burning vegetation releases fuel gas that burns in the model, and the resulting plume interacts with the surrounding air.<ref name="FDS-139">McGrattan et al. (2026), p. 139.</ref>

Such predictions are only as good as their input, because a fire model predicts fire effects from data chosen by the user. Its estimates are technically credible only when the conditions for which the model was developed are not violated. Model outputs are single values that do not show the uncertainty in the inputs.<ref name="Notarianni">Notarianni (2002), p. 5-43.</ref>

== Suppression ==

One of the glossary definitions quoted in NUREG-1805 describes fire suppression as all the work of confining and extinguishing wildland fires.<ref name="NUREG-F" /> In the United States, wildfire control has its own NFPA standards. Examples listed in NUREG-1805 are NFPA 295, Standard for Wildfire Control (1998 edition), and NFPA 1051 on the professional qualifications of wildland fire fighters (2002 edition). Others cover wildland fire apparatus (NFPA 1906, 2001 edition) and protective clothing and equipment for wildland fire fighting (NFPA 1977, 1998 edition).<ref name="NUREG-E">Iqbal and Salley (2004), pp. E-6, E-10, E-12.</ref> Putting out the flames is not always the end, because smouldering in the duff layer can re-ignite a flaming fire.<ref name="Ohlemiller" />

Class A foams, intended for ordinary combustibles such as wood, have been used widely in wildland fire suppression.<ref name="NUREG-B58">Iqbal and Salley (2004), pp. B-58–B-59.</ref> Their success with fires in natural cover fuels led to research on their use in buildings.<ref name="Scheffey">Scheffey and Hickey (2002), p. 4-144.</ref> In wildland use they are generally mixed with water at 0.1 to 1.0 per cent and applied with compressed air foam systems through hose lines.<ref name="NUREG-B60">Iqbal and Salley (2004), p. B-60.</ref> Foam keeps air away from the fire, produces steam, penetrates crevices and protects exposed material that is not yet burning. It is, however, unstable. Physical or mechanical forces break it down, heat drives out its water, and turbulent air can blow light foam away from the burning area.<ref name="NUREG-B58" />

== See also ==

* [[Facade fire]]
* [[Warehouse fire]]
* [[Car park fire]]

== Notes ==

<references />

== References ==

* Cox, G., & Kumar, S. (2002). Modeling enclosure fires using CFD. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-194–3-218). National Fire Protection Association; Society of Fire Protection Engineers.
* Hamins, A., Maranghides, A., McGrattan, K. B., Ohlemiller, T. J., & Anleitner, R. L. (2005). ''Experiments and modeling of multiple workstations burning in a compartment'' (NIST NCSTAR 1-5E). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Kanury, A. M. (2002a). Flaming ignition of solid fuels. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-229–2-245). National Fire Protection Association; Society of Fire Protection Engineers.
* McGrattan, K., Hostikka, S., Floyd, J., McDermott, R., Vanella, M., Mueller, E., & Paul, C. (2026). ''Fire Dynamics Simulator technical reference guide: Vol. 1. Mathematical model'' (6th ed., NIST Special Publication 1018-1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.1018
* Ministry of Business, Innovation and Employment. (2013). ''Commentary for Building Code clauses C1–C6 and Verification Method C/VM2''.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* Najafi, B., Joglar, F., & Dreisbach, J. (2007). ''Verification and validation of selected fire models for nuclear power plant applications: Vol. 1. Main report'' (NUREG-1824; EPRI 1011999). U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research; Electric Power Research Institute.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-200–2-210). National Fire Protection Association; Society of Fire Protection Engineers.
* Quintiere, J. G. (2002b). Surface flame spread. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-246–2-257). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L., & Hickey, H. E. (2002). Foam system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-123–4-148). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Special Hazards & Building Types]]

Forensic fire reconstruction

2026-11-02T18:10:27Z

Mark: Redirect to Fire investigation (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire investigation]]

Fire reconstruction

2026-11-02T18:10:21Z

Mark: Redirect to Fire investigation (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire investigation]]

Post-fire investigation

2026-11-02T18:10:15Z

Mark: Redirect to Fire investigation (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire investigation]]

Dust explosion

2026-11-02T18:10:08Z

Mark: Revise against the FSE wiki writing guidelines: abbreviation written out (revised by Claude Opus 5.5)

A '''dust explosion''' is an [[explosion]] of a cloud of combustible dust or powder suspended in air. Once the cloud is ignited, flame spreads through it, and in a confined space the hot combustion gases cannot expand freely, so the pressure rises rapidly.<ref name="Z402">Zalosh (2002), p. 3-402.</ref><ref name="Z403">Zalosh (2002), p. 3-403.</ref> Dusts known to explode include food powders such as sugar, corn starch and milk powder, as well as coal, plastics and metal powders such as aluminium.<ref name="Z404">Zalosh (2002), p. 3-404.</ref> In closed test vessels, twenty representative dusts reached maximum pressures of 6.7 to 11.2 bar above atmospheric pressure, about the same range as flammable gases.<ref name="Z407">Zalosh (2002), p. 3-407.</ref>

The cloud can be ignited by sparks, static electricity, hot surfaces or dust deposits that heat up by themselves.<ref name="Z405">Zalosh (2002), p. 3-405.</ref><ref name="IS-15-3">Iqbal and Salley (2004), p. 15-3.</ref> A first explosion inside equipment can also lift settled dust into a new cloud, and the resulting secondary explosion in an occupied building can cause many casualties.<ref name="Z409-410">Zalosh (2002), pp. 3-409–3-410.</ref> Protection relies on avoiding explosive clouds, removing ignition sources, inerting, and limiting the pressure by venting, suppression or an enclosure strong enough to resist it.<ref name="Z402" /><ref name="IS-F20">Iqbal and Salley (2004), p. F-20.</ref>

== How a dust cloud burns ==

A dust explosion first needs a cloud, and some disturbance or air movement is always needed to raise dust into the air.<ref name="Z409">Zalosh (2002), p. 3-409.</ref> Once the cloud is ignited, flame travels through the mixture of dust and air. In an enclosure the confinement stops the hot combustion products from expanding freely.<ref name="Z402" /> Ignition of a dust cloud in an unvented enclosure usually produces a deflagration, a flame that moves away from the ignition point slower than sound.<ref name="Z406">Zalosh (2002), p. 3-406.</ref> For dust as for gas, the pressure reached depends on how far the flame has spread and on the temperature and composition of the burned gas.<ref name="Z406" /> NUREG-1805, a fire hazard analysis guide of the US Nuclear Regulatory Commission, lists dust explosions among the combustion explosions, together with gas, mist and backdraft explosions.<ref name="IS-15-2">Iqbal and Salley (2004), p. 15-2.</ref>
[[File:fse-dust-explosion-v1.svg|thumb|upright=1.5|alt=Air movement suspends dust, ignition propagates flame and confinement raises pressure.|A dust explosion requires dispersion, ignition and flame propagation. Based on Zalosh (2002), pp. 3-402–3-406.]]

For organic dusts, the particles have to give off flammable vapour first, and the flame then burns in the gas phase.<ref name="Beyler-182">Beyler (2002b), p. 2-182.</ref><ref name="Beyler-183">Beyler (2002b), p. 2-183.</ref> This need to turn the fuel into vapour is why the lower flammable limit of a dust is expected to be higher than that of a comparable gas.<ref name="Beyler-182" /> For very small particles the limit no longer depends on particle size and comes close to that of the matching gas, provided all of the fuel turns into vapour.<ref name="Beyler-182" /> Metal and graphite dusts are different, because for them burning on the surface of the particles plays an important part in spreading the flame.<ref name="Beyler-183" />

Turbulence has an even larger effect on the rate of pressure rise in dust explosions than in gas explosions, because some motion is always needed to raise the cloud.<ref name="Z409" /> Dust particles also take a finite time to burn, which gives a dust flame a finite thickness.<ref name="Z409" /> A mixture of a combustible gas with a combustible dust is called a hybrid mixture. Explosion venting is used for such mixtures as well as for gases, dusts and mists.<ref name="IS-F37">Iqbal and Salley (2004), p. F-37.</ref><ref name="Z414">Zalosh (2002), p. 3-414.</ref> When fire spreads rapidly through a dust cloud without producing damaging pressure, the event is called a flash fire.<ref name="IS-F32">Iqbal and Salley (2004), p. F-32.</ref>

== When dust can explode ==

Not every dust cloud can explode. Combustible dusts and powders pose an explosion hazard when their typical particle size is below 100 to 400 micrometres, depending on how combustible the material is.<ref name="Z403" /> The concentration must also lie between the lower and upper explosive limits. For dusts finer than about 100 micrometres the lower limit is typically 30 to 60 g/m³, roughly the same as for many flammable gases in these units.<ref name="Z403" /> The upper limit is typically 2,000 to 6,000 g/m³, but it is difficult to measure and even more difficult to use as a means of prevention.<ref name="Z403" /> In Zalosh's table of representative dusts, mostly tested in a 1 m³ vessel, the minimum explosible concentration ranges from 15 g/m³ for naphthalene and phenolic resin to 250 g/m³ for zinc.<ref name="Z404" />

Smaller particles generally lower the minimum explosible concentration, until a limiting size is reached below which it falls no further.<ref name="Z404" /> Above that size, burning appears to be limited by how fast the particles give off vapour, which depends on their surface area. Below it, the chemistry of the gas flame seems to set the limit.<ref name="Z404" /> For a given material and particle size, the minimum explosible concentration falls steadily as the temperature rises.<ref name="Z404" /> For bituminous coal the lower limit stays well above the 48 g/m³ typical of gaseous hydrocarbons, because not all of the coal turns into vapour. It is not expected to fall below 50 g/m³ even in pure oxygen.<ref name="Beyler-182" />

The most violent explosions do not occur at the lower limit. The concentration that gives the highest pressure is often about 500 g/m³. For many organic materials this is roughly twice the amount needed for complete burning and five to ten times the minimum explosible concentration.<ref name="Z407" />

Concentrations in real plants are often unknown or deceptively low. In a plastic powder silo, for example, concentrations can become much higher than those measured during normal filling and emptying. This can happen when vibration or air blasts are used to free blocked powder.<ref name="Z404" /> A worked example compares two coal mills. The dust leaving one mill, at 0.27 kg/m³, is well inside the explosive range. The other, at 1.96 kg/m³, is close to the upper limit of 2 to 4 kg/m³ reported for coal.<ref name="Z405" />

== Ignition sources ==

The [[minimum ignition energy]] of a dust cloud is measured with an electric spark in a 1.2-litre tube, sometimes called a modified Hartmann tube.<ref name="Z405" /> For the dusts in Zalosh's table with measured values, it ranges from less than 1 mJ to more than 2,000 mJ.<ref name="Z405" /> NUREG-1805 states that a dust cloud may ignite with as little as 20 mJ, compared with 0.3 mJ for a flammable gas or vapour.<ref name="IS-C1">Iqbal and Salley (2004), p. C-1.</ref> Several dusts in Zalosh's table need even less, such as sugar at 14 mJ and naphthalene at less than 1 mJ.<ref name="Z404" /> Longer sparks ignite dust more easily: adding inductance or resistance to the circuit can lower the minimum ignition energy tenfold. An electrostatic discharge therefore needs more energy to ignite a dust cloud than a spark from an electrical switch.<ref name="Z405" />

Static electricity is a real hazard in powder handling. In a worked example, a poorly earthed silo would have to reach about 14 kV before its spark could ignite a powder needing 50 mJ from a capacitive discharge. Friction and impact of the powder during filling and emptying can produce such voltages.<ref name="Z405" /> Earthing the silo prevents charge from building up on the silo itself. Charge can still collect, however, on ungrounded objects inside it and possibly on powder with a high electrical resistance.<ref name="Z405-406">Zalosh (2002), pp. 3-405–3-406.</ref>

Hot surfaces are a second group of ignition sources. The minimum ignition temperature of a dust cloud is measured by blowing dust through a heated vertical tube. Most dusts in Zalosh's table ignite between 440 °C and 750 °C.<ref name="Z404" /> A dust layer 5 mm thick on a hot plate often ignites at a significantly lower temperature, because a layer loses heat less easily than a cloud.<ref name="Z404" /><ref name="Z405" /> Siwek and Cesana's data suggest that a hot spot of at least 900 °C, for example from friction in a mill, can ignite a cloud with an ignition temperature below 600 °C.<ref name="SC">Siwek and Cesana (1995), as cited in Zalosh (2002), p. 3-405.</ref> Sparks from friction and impact, by contrast, only ignite dusts with a minimum ignition energy below 10 mJ and an ignition temperature below 500 °C.<ref name="SC" />

Dust can also ignite itself. Deposits on hot process surfaces can undergo accelerated self-heating and eventually ignite.<ref name="IS-15-3" /> In a milk-drying plant, the air entering a spray dryer was heated to 200 °C, and surfaces near the inlet might reach this temperature too. Powder collecting on such hot surfaces could ignite spontaneously and then act as the ignition source for a dust explosion. Such explosions have occurred in milk-drying plants with devastating consequences.<ref name="Beever">Beever (1988), as cited in Gray (2002), p. 2-226.</ref> Smouldering in grain silos is a related problem, and it must be completely extinguished before a silo is emptied, to avoid the possibility of a dust explosion.<ref name="Ohlemiller">Ohlemiller (2002), p. 2-207.</ref>

== Explosion pressure and the deflagration index ==

In standard closed-vessel tests, the maximum pressures of the twenty dusts in Zalosh's table range from 6.7 bar for zinc to 11.2 bar for aluminium.<ref name="Z404" /> For three of the four dusts in one test series, the maximum pressure did not change as long as the median particle size was no more than 100 micrometres.<ref name="Z407" /> Polyvinyl chloride (PVC) dust, which is significantly less combustible than the other three, gave lower pressures above 20 micrometres and could not be ignited at all from 150 micrometres.<ref name="Z407" />

The rate of pressure rise matters for protection, because the vent area needed depends on it as well as on the size of the enclosure.<ref name="Z414" /> The rate of pressure rise depends mainly on how fast the flame spreads, on the size of the vessel and on the flame temperature.<ref name="Z407" /> The maximum rate of pressure rise measured in a closed vessel, scaled by the size of the vessel, is expressed as the [[deflagration index]], KSt, in bar·m/s.<ref name="Z409" />

Some venting models use the index to represent how fast a dust burns.<ref name="Z414" /> In the vent sizing equation proposed for the 2002 edition of NFPA 68, the US venting guide of the National Fire Protection Association, the vent area increases in proportion to KSt.<ref name="Z416">Zalosh (2002), p. 3-416.</ref><ref name="Z417">Zalosh (2002), p. 3-417.</ref> In Zalosh's table, aluminium has the highest value at 515 bar·m/s. The other dusts lie between 28 and 209 bar·m/s, with corn starch at 128 and coal at 59.<ref name="Z404" />

The turbulence in a test vessel is highest when the dust is first blown in and decays by the time the whole cloud has entered. The delay between dust injection and ignition therefore changes the measured pressures.<ref name="Z409" /> A standard test method was developed so that different vessels and laboratories obtain reproducible results.<ref name="Z409" /> In the United States, the American Society for Testing and Materials standard ASTM E1226 (1988 edition) is used for KSt in a 20-litre vessel.<ref name="Z415">Zalosh (2002), p. 3-415.</ref> ASTM E1515 (1998 edition) specifies a pyrotechnic igniter of 2,500 or 5,000 J in a 20-litre vessel for the minimum explosible concentration. Some materials are so sensitive to the igniter that tests in a 1 m³ vessel are needed.<ref name="Z404" />

== Secondary explosions ==

Dust explosions have a particular tendency to cause damaging secondary explosions.<ref name="Z409" /> A first explosion can burst a piece of process equipment that cannot withstand the full closed-vessel pressure, sending out a blast wave and strong air movement. This disturbance often lifts dust that has settled on walls and floors into a new cloud.<ref name="Z409" /> Even if this cloud fills only a small part of the building, the flame escaping from the broken equipment often ignites it.<ref name="Z409" /> In an occupied building, the secondary explosion can cause many casualties as well as structural damage.<ref name="Z409-410" />
[[File:fse-dust-explosion-v2.svg|thumb|upright=1.5|alt=A primary vessel explosion lifts building dust into a cloud that ignites in a secondary explosion.|Secondary explosions can involve dust accumulated outside the original equipment. Based on Zalosh (2002), pp. 3-409–3-410.]]

A thin layer of dust can be enough. In a worked example, Zalosh considers bituminous coal dust lying on the floor at 1,000 g/m², a layer about 2 mm thick, in a room with a 4 m ceiling.<ref name="Z410">Zalosh (2002), p. 3-410.</ref> Suppose a first explosion lifts this dust into a worst-case cloud of 500 g/m³ in the lower part of the room. Without venting, the secondary explosion then raises the pressure by about 4.6 bar.<ref name="Z410" /> That is at least thirty times the 7 to 15 kPa at which unrestrained brick walls typically fail.<ref name="Harris">Harris (1983), as cited in Iqbal and Salley (2004), p. 15-13.</ref> NUREG-1805 also lists secondary explosions leading to catastrophic damage among the hazards of a deflagration, together with equipment failure and injury.<ref name="IS-15-3" />

== Prevention and protection ==

Dust explosion protection interrupts the chain of events at one of three points: preventing an explosive cloud, removing ignition sources, or limiting the pressure rise.<ref name="Z402" /> Where the dust concentration in equipment cannot be kept below the minimum explosible concentration, [[inerting]] adds an inert gas to lower the oxygen concentration.<ref name="Z404" /> With carbon dioxide, the limiting oxygen concentration for organic dusts lies between 11 and 15 per cent by volume, but the values for some metals are much lower.<ref name="Z404" /> Zirconium powder has a limit of zero, a sign of pyrophoric behaviour, that is, spontaneous combustion on exposure to air.<ref name="Z404" /><ref name="IS-F47">Iqbal and Salley (2004), p. F-47.</ref> In the United States, NFPA 69 (1997 edition) states that oxygen should be kept at least 2 percentage points below the limit under continuous monitoring, and further below it otherwise.<ref name="Z403" />

Ignition sources are controlled, for example, by earthing equipment to prevent electrostatic discharges.<ref name="Z402" /> In the coal mill example, a temperature monitor could stop the mill well before friction or smouldering coal heated its wall to 600 °C.<ref name="Z405" /> In the [[hazardous area classification]] summarised in NUREG-1805, a US guide, Division 1 covers places where flammable gases or combustible dust may be present at ignitable concentrations during normal operation.<ref name="IS-B24">Iqbal and Salley (2004), p. B-24.</ref> NFPA 499 (1997 edition) is a US recommended practice for classifying combustible dusts and such locations for electrical installations in chemical process areas.<ref name="IS-E">Iqbal and Salley (2004), pp. E-3, E-8.</ref>

[[Explosion venting]] releases the combustion gases through openings, usually covered by panels or rupture discs, so that the pressure stays below the level that would damage the enclosure.<ref name="Z414" /> Perhaps the most extensive large-scale venting tests were those of Bartknecht and colleagues in Basel, Switzerland, mostly with dusts in vessels of 2.4 to 250 m³.<ref name="Z415" /> They used energetic igniters and worst-case dust concentrations, and their data were correlated in the various versions of VDI 3673, the dust venting guideline of the Association of German Engineers (VDI).<ref name="Z415" /><ref name="Z421">Zalosh (2002), p. 3-421.</ref> For low-strength enclosures, NFPA 68 (1998 edition) groups dusts by their deflagration index: below 200, from 200 to 300, and above 300 bar·m/s.<ref name="Z416" /> In one worked example, a 400 m³ electrostatic precipitator in a coal-fired power plant needed about 2 m² of vent area.<ref name="Z416-417">Zalosh (2002), pp. 3-416–3-417.</ref> Because KSt can vary widely even between coals, Zalosh stresses that the vent area should be based on samples from the actual site.<ref name="Z417" />

Explosion suppression detects an explosion in its first moments, usually with pressure detectors for dust, and discharges an extinguishing agent before the pressure reaches the damage threshold.<ref name="Z417" /> Unlike venting it releases no flame or fuel, so it suits indoor equipment, but it is costly.<ref name="Z417" /> The remaining pressure is usually below 5 per cent of the unsuppressed maximum for organic fuels. For aluminium dust, the most demanding material tested, recent tests suggest that it can now be kept to 10 to 20 per cent.<ref name="Z418">Zalosh (2002), p. 3-418.</ref> Work with dried milk powders at an Irish agricultural research facility has given evidence that water mist with very small drops may quell a dust explosion.<ref name="MB">Mawhinney and Back (2002), p. 4-330.</ref> Deflagration pressure containment instead designs a vessel and its fittings to withstand the full pressure of an internal deflagration.<ref name="IS-F20" />
[[File:fse-dust-explosion-v3.svg|thumb|upright=1.5|alt=Five layers address cloud formation, ignition, oxygen, pressure relief and vessel strength.|Dust-explosion protection acts at different points in the event sequence. Based on Zalosh (2002), pp. 3-402–3-403 and pp. 3-414–3-416.]]

== Test data and their limits ==

Explosibility data are measured in standard laboratory tests. Results depend on the ignition source, on the turbulence at the moment of ignition, and on the size and shape of the test vessel.<ref name="Z404" /><ref name="Z414" /> For a hazard evaluation, Barry lists dust explosion data for samples that reflect the process conditions among the material properties needed.<ref name="Barry">Barry (2002), p. 5-178.</ref> Two samples of the same material can behave very differently. In Zalosh's table, polyethylene with a median particle size below 10 micrometres has a KSt of 156 bar·m/s, against 54 bar·m/s for a sample of 150 micrometres.<ref name="Z404" />

Dust explosions are more difficult to model than gas explosions.<ref name="Z414" /> Venting guidelines are based on tests and do not account for the turbulence and equipment obstructions of a particular installation. Most of them also ignore how much of the enclosure is filled with the combustible mixture.<ref name="Z416" /> The vent area calculated in the precipitator example also does not allow for the weight of the vent panels.<ref name="Z417" />

Risk indexing methods for process plants take dust into account. The Dow Fire and Explosion Index adds a penalty for a dust explosion hazard. It counts this among its special process hazards, the items that increase the probability of a fire or explosion.<ref name="Watts">Watts (2002), pp. 5-129–5-130.</ref> NUREG-1805 also lists several NFPA standards that deal with dust explosions. They include NFPA 654 (2000 edition) on combustible particulate solids, NFPA 61 (2002 edition) on agricultural and food products facilities, and NFPA 484 (2002 edition) on combustible metals and metal dusts.<ref name="IS-E" />

== See also ==

* [[Self-heating]]
* [[Deflagration]]
* [[Detonation]]
* [[Vapour cloud explosion]]

== Notes ==

<references />

== References ==

* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-176–5-213). National Fire Protection Association; Society of Fire Protection Engineers.
* Beyler, C. L. (2002b). Flammability limits of premixed and diffusion flames. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-172–2-187). National Fire Protection Association; Society of Fire Protection Engineers.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-211–2-228). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Mawhinney, J. R., & Back, G. G., III. (2002). Water mist fire suppression systems. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-311–4-337). National Fire Protection Association; Society of Fire Protection Engineers.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-200–2-210). National Fire Protection Association; Society of Fire Protection Engineers.
* Watts, J. M., Jr. (2002). Fire risk indexing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-125–5-142). National Fire Protection Association; Society of Fire Protection Engineers.
* Zalosh, R. (2002). Explosion protection. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-402–3-421). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Explosions & Industrial Fires]]

Fire cause investigation

2026-11-02T18:10:02Z

Mark: Redirect to Fire investigation (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire investigation]]

Explosion

2026-11-02T18:09:56Z

Mark: Revise against the FSE wiki writing guidelines: abbreviation written out (revised by Claude Opus 5.5)

An '''explosion''' is a rapid, potentially damaging rise in pressure, such as the one that follows when a combustible gas, vapour or dust mixed with air in a confined space is ignited. The flame travels through the mixture, and the confinement stops the hot combustion products from expanding freely.<ref name="Z402">Zalosh (2002), p. 3-402.</ref> NUREG-1805, a fire hazard analysis guide of the US Nuclear Regulatory Commission, gives a broader definition: a sudden and violent release of high-pressure gases into the surroundings.<ref name="IS-15-1">Iqbal and Salley (2004), p. 15-1.</ref> This definition does not depend on what produced the pressure.<ref name="IS-15-1" /> Explosions are often grouped into physical explosions, such as a heated tank that bursts, and chemical explosions, such as a burning cloud of gas or dust.<ref name="IS-15-2">Iqbal and Salley (2004), p. 15-2.</ref>

Explosions matter in fire safety because ordinary buildings are weak against pressure. Glass windows typically fail at 2 to 7 kPa, whereas a premixed gas-air mixture ignited inside a building can produce up to about 8 bar, or 800 kPa.<ref name="Harris">Harris (1983), as cited in Iqbal and Salley (2004), p. 15-13.</ref><ref name="IS-15-12">Iqbal and Salley (2004), p. 15-12.</ref> Engineers distinguish a [[deflagration]], in which the flame moves slower than sound, from a [[detonation]], in which it moves faster, because the two need different protection.<ref name="Z410">Zalosh (2002), p. 3-410.</ref><ref name="Z411">Zalosh (2002), p. 3-411.</ref> Protection works by preventing a flammable mixture, by removing ignition sources, or by limiting the pressure through venting, suppression or an enclosure strong enough to resist it.<ref name="Z402" /><ref name="IS-F20">Iqbal and Salley (2004), p. F-20.</ref>

== What counts as an explosion ==

In its most widely accepted sense, an explosion is a bursting with a loud, sharp noise and an expanding pressure front, ranging from a supersonic shock wave to a relatively mild wind.<ref name="IS-15-1" /> The NUREG-1805 definition rests on two ideas. The gas must be at a higher pressure than its surroundings, and it must be released so fast that its energy escapes as a shock wave.<ref name="IS-15-1" /> The stored energy can be nuclear, chemical, electrical or pressure energy. A release counts as an explosion only if it produces a pressure wave that can be heard, even if it causes no damage.<ref name="IS-15-2" />

The rate of release decides how violent an explosion is. The energy stored in a car tyre can cause an explosive burst, but the same energy can also be released gradually.<ref name="IS-15-16">Iqbal and Salley (2004), p. 15-16.</ref> In a combustion explosion the confinement keeps the hot gases from expanding freely.<ref name="Z402" /> The normal openings of process equipment are usually too small to prevent destructive pressures.<ref name="IS-15-3">Iqbal and Salley (2004), p. 15-3.</ref>

Explosions are often classified by how the high-pressure gas is produced.<ref name="IS-15-2" /> In a physical explosion the pressure comes from mechanical means without any chemical change. Examples are a tank that fails after external heating has raised its internal pressure, and a superheated liquid that is suddenly released and flashes into vapour.<ref name="IS-15-2" /> A pressure vessel that ruptures without its gas igniting also causes a physical explosion, driven by the expansion of the gas to atmospheric pressure.<ref name="Z419">Zalosh (2002), p. 3-419.</ref> In a chemical explosion the pressure comes from a chemical reaction. This group includes combustion explosions of dust, gas, mists and backdraft gases, thermal explosions in runaway reactions, and explosions of high explosives and propellants.<ref name="IS-15-2" />

== How a gas or dust explosion develops ==

For a deflagration, NUREG-1805 names three things that must be present at the same time: a flammable mixture of fuel and oxygen, usually from air, a means of ignition, and an enclosure.<ref name="IS-15-3" /> The mixture can only explode between its lower and upper explosion limits, which are also called flammability limits.<ref name="IS-15-4">Iqbal and Salley (2004), p. 15-4.</ref> Outside this range a flame cannot spread through it.<ref name="IS-15-4" /> All glowing sparks are hot enough to ignite a mixture, but some carry too little energy, while a hot process surface may be cooler yet hold a large amount of energy.<ref name="IS-15-3" />

Once ignited, the flame spreads through the mixture and heats the gas it passes.<ref name="Z402" /> For a hydrocarbon fuel mixed with exactly enough air for complete burning, the temperature rises from 300 K to about 2,200 K.<ref name="Simmons">Simmons (2002), p. 1-147.</ref> If no heat is lost, the pressure in a closed vessel can then climb to a little over 7 bar. A vessel that is not designed for such pressures will rupture.<ref name="Simmons" /> Measured maximum pressures for ten of twelve flammable gases and vapours lie between 6.8 and 8.1 bar above atmospheric pressure.<ref name="Z407">Zalosh (2002), p. 3-407.</ref> Near the flammability limits the pressures are lower, because the flame burns only part of the enclosure and heat is lost to the walls.<ref name="Z406">Zalosh (2002), pp. 3-406–3-407.</ref>

The pressure does not rise evenly. In a worked example by Zalosh for a spherical vessel 7.15 m in radius, the pressure had risen by only about 14 kPa when the flame was halfway to the wall. The final rise was about 640 kPa.<ref name="Z408">Zalosh (2002), pp. 3-408–3-409.</ref> In that example most of the pressure rise happened at the end, when flame filled almost the whole vessel.<ref name="Z408" /> Reaching the maximum pressure can take up to a few hundred milliseconds, depending on the size of the enclosure and the fuel.<ref name="IS-15-3" /> With connected vessels, burning in one vessel raises the pressure in the next, and a flame that then enters it produces a correspondingly higher pressure.<ref name="Simmons" />

Explosions in the open air, called unconfined explosions, differ fundamentally from confined explosions in vessels, pipework or buildings, and need different countermeasures.<ref name="IS-15-5">Iqbal and Salley (2004), p. 15-5.</ref> When a gas leaks into the open, mixes with air and is ignited, the flame front spreads through the cloud as a sphere wherever it can.<ref name="IS-15-6">Iqbal and Salley (2004), p. 15-6.</ref> Inside a building, gases rushing out through a vent, door or window can create turbulence that produces a second pressure peak.<ref name="IS-15-5" />

== Deflagration and detonation ==

A deflagration is an explosion in which the reaction spreads through the mixture by heat, at a speed below the speed of sound. It is slower than a detonation but can still cause damage.<ref name="IS-F20" /> In a detonation the combustion zone travels faster than sound through the unburned mixture.<ref name="IS-F21">Iqbal and Salley (2004), p. F-21.</ref> A shock wave runs ahead of the reaction and compresses the gas, which speeds up the reaction.<ref name="IS-15-3" /> A deflagration flame moves well below the speed of sound, about 340 m/s in room-temperature air, so its pressure rises almost evenly throughout an enclosure.<ref name="Z410" /> In a detonation the pressure rise is very uneven and almost instantaneous as the shock passes each point.<ref name="Z410" />
[[File:fse-explosion-v1.svg|thumb|upright=1.5|alt=Deflagration fills a vessel over time; detonation produces a sharp local shock front.|Deflagration and detonation create different pressure conditions. Based on Zalosh (2002), pp. 3-410–3-411 and Iqbal and Salley (2004), pp. F-20–F-21.]]

Typical detonation speeds are about 1,500 to 3,000 m/s, and NUREG-1805 gives a value of the order of 2,000 m/s.<ref name="Simmons" /><ref name="IS-15-3" /> In a gas mixture that starts at atmospheric pressure, the pressure just behind a detonation can be up to 20 bar.<ref name="Simmons" /> Zalosh notes that this is roughly twice the pressure of the same mixture burning in a closed vessel.<ref name="Z411" /> Where a detonation is reflected from the closed end of a duct, the pressure can be up to 100 bar. Detonations are therefore much more destructive than an ordinary moving flame.<ref name="Simmons" />

The difference matters for protection. The sudden, uneven pressure rise of a detonation rules out explosion venting and explosion suppression, and its high, short pressure peaks need a special structural assessment.<ref name="Z411" /> Most accidental explosions are deflagrations, and NUREG-1805 describes detonations as very rare.<ref name="Z413">Zalosh (2002), p. 3-413.</ref><ref name="IS-15-12" /> The minimum energy needed to start a detonation directly ranges from about 5 kJ for acetylene or hydrogen in air to an estimated 93,000 kJ for methane. These energies are far greater than those of accidental ignition sources.<ref name="Z412">Zalosh (2002), p. 3-412.</ref>

A deflagration can, however, accelerate and turn into a detonation, especially in long pipes, elongated enclosures or very turbulent conditions.<ref name="Z412" /> This deflagration-to-detonation transition comes sooner with a more reactive mixture, rough walls or obstacles, a larger diameter, a higher starting pressure or temperature, and more turbulence.<ref name="Z412" /><ref name="Z413" /> In tests with petrol vapour and air, a smooth pipe 15 cm wide and 16 m long gave no transition. A rough liner at the pipe entrance, however, produced a detonation after 74 pipe diameters.<ref name="Z413" /> Because the protection differs so much, Zalosh stresses that the possibility of a detonation has to be assessed, although there are no exact criteria for doing so.<ref name="Z412" />

== Explosion scenarios in fire safety ==

A [[dust explosion]] occurs in a cloud of combustible powder suspended in air. Dusts pose this hazard when their typical particle size is below about 100 to 400 micrometres, depending on the material.<ref name="Z403">Zalosh (2002), p. 3-403.</ref> The concentration must also lie between the lower and upper explosive limits, and for dusts finer than about 100 micrometres the lower limit is typically 30 to 60 g/m³.<ref name="Z403" /> A particular danger is the secondary explosion, in which a first explosion bursts a piece of equipment and its blast lifts dust that has settled on walls and floors.<ref name="Z409">Zalosh (2002), pp. 3-409–3-410.</ref> Flame escaping from the equipment often ignites this new cloud, which in an occupied building can cause many casualties and structural damage.<ref name="Z409" />

A [[vapour cloud explosion]] occurs when a very large cloud of flammable gas or vapour is ignited in a congested area, such as a chemical plant crowded with process equipment and storage vessels.<ref name="Z420">Zalosh (2002), p. 3-420.</ref> In risk studies of process plants, it usually involves more than about a tonne of flammable vapour, which forms a large cloud and explodes after delayed ignition.<ref name="Barry-184">Barry (2002), p. 5-184.</ref> The strength of its blast depends on the flame speed that develops and on how strongly the cloud is confined.<ref name="Z420" /> In a flash fire the flame is slower: it spreads quickly through the flammable part of the cloud but causes no blast damage.<ref name="Barry-184" />

A [[BLEVE]], short for boiling liquid expanding vapour explosion, occurs when a pressurised vessel of liquefied gas ruptures and the liquid suddenly expands into gas, producing blast waves.<ref name="IS-5-15">Iqbal and Salley (2004), p. 5-15.</ref> It typically happens when the metal of a container has been overheated above about 538 °C. Usually only the wall around the vapour space is at risk, because the liquid absorbs heat from the wetted wall.<ref name="IS-5-15" /> Barry describes it as a delayed event that generally follows 8 to 15 minutes of exposure to a fire.<ref name="Barry-184" /> The bursting vessel throws fragments and sends out a blast wave, and most BLEVEs also produce a rising fireball.<ref name="Z419" /> Fireballs in accidents with liquefied petroleum gas have usually been of the order of 100 m across and have lasted a few seconds.<ref name="Beyler">Beyler (2002a), p. 3-303.</ref>
[[File:fse-explosion-v2.svg|thumb|upright=1.5|alt=Heated vessel fails, releasing expanding vapour, fragments, blast and a fireball.|A BLEVE combines physical expansion with several possible hazards. Based on Iqbal and Salley (2004), p. 5-15 and Zalosh (2002), p. 3-419.]]

Fires inside buildings can produce explosions of their own. When a fire is short of air, unburned pyrolysis gases can collect and form, once mixed with air, a flammable mixture that needs only ignition energy.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref> A [[smoke explosion]] is the very rapid burning of such gases from decomposed or incompletely burned fuel.<ref name="VR-4.10">Van Rossum (2027), §4.10.</ref> It typically requires the gases and air to be reasonably premixed within the explosion limits, and it can be ignited by a spark, by glowing particles or by autoignition.<ref name="VR-4.10" /> A backdraft is different: hot fire gases that lack only oxygen ignite explosively when fresh air suddenly enters, for example when a door is opened.<ref name="VR-4.9">Van Rossum (2027), §4.9.</ref> NUREG-1805 adds that a backdraft behaves like a premixed fuel-air deflagration, and that smoke explosions have been observed in smouldering polyurethane foam fires.<ref name="IS-15-4" />

Electric vehicles add a newer example. Battery cells in thermal runaway release flammable gases. If these do not ignite at once, they can build up into an explosive mixture in a confined or poorly ventilated space.<ref name="VdG-27">Van der Graaf et al. (2021/2023), p. 27.</ref> When the mixture reaches its lower explosion limit and is ignited, a fire gas explosion can occur.<ref name="VdG-27" /> Fires in electric vehicles can also involve repeated minor explosions, flying parts and flash fires.<ref name="VdG-29">Van der Graaf et al. (2021/2023), p. 29.</ref>

== Effects on people and buildings ==

An explosion sends out a blast wave, a thin shell of strongly compressed air and hot gases that spreads in all directions. It can travel faster than sound, which is why a large explosion is heard as a loud bang.<ref name="IS-15-7">Iqbal and Salley (2004), p. 15-7.</ref> Its strength is expressed as the peak overpressure, the highest pressure in the wave above normal atmospheric pressure.<ref name="IS-15-7" /> This overpressure is highest near the source and falls quickly with distance, and nearby reflecting surfaces strongly influence the damage.<ref name="IS-15-7" /> An explosion can also cause heat damage, damage from flying objects, ground shock, craters and injuries, although not every explosion does all of these.<ref name="IS-15-8">Iqbal and Salley (2004), p. 15-8.</ref>

Buildings fail at low overpressures. Typical failure pressures are 2 to 3 kPa for room doors, 2 to 5 kPa for light partition walls and 7 to 15 kPa for unrestrained brick walls.<ref name="Harris" /> A gas explosion inside a building, at up to about 800 kPa, can therefore exceed the strength of such elements many times over.<ref name="IS-15-12" /> For process plants, Barry lists about 3.4 to 6.9 kPa (0.5 to 1 psi) as causing glass damage and injuries from flying glass. He gives 17 to 34 kPa (2.5 to 5 psi) for heavy damage to buildings and process equipment.<ref name="Barry-186">Barry (2002), p. 5-186.</ref>

People can withstand fairly high blast pressures, and when blast waves kill people it is usually through falling objects rather than through the pressure itself.<ref name="IS-15-12" /> Data quoted in NUREG-1805 give about 35 kPa as the threshold for eardrum rupture and about 70 kPa for lung damage.<ref name="Fischer">Fischer et al. (1995), as cited in Iqbal and Salley (2004), p. 15-12.</ref> The blast can also hurl fragments and debris, and it can throw people against the ground, walls or other fixed objects.<ref name="IS-15-9">Iqbal and Salley (2004), p. 15-9.</ref> NUREG-1805 notes that the consequences for people depend strongly on whether anything nearby can strike them.<ref name="IS-15-12" />

A common way to estimate blast effects is to express an explosion as an equivalent mass of TNT (trinitrotoluene), whose blast effects have been studied in detail.<ref name="IS-15-10">Iqbal and Salley (2004), p. 15-10.</ref> Such methods treat the explosion as an ideal blast released at a single point.<ref name="Z419" /><ref name="IS-15-15">Iqbal and Salley (2004), p. 15-15.</ref> They cannot be valid inside or close to a flammable vapour cloud.<ref name="IS-15-15" /> For vapour cloud explosions the real blast also weakens far less quickly with distance than an ideal one.<ref name="Z420" /> Current methods instead estimate the flame speed for the type of application, or use computer models that calculate how the flame spreads and accelerates.<ref name="Z420" />

== Prevention and protection ==

Explosion protection interrupts the chain of events that leads to an explosion. It can prevent a flammable fuel-air mixture from forming, for example by ventilation or [[inerting]]. It can remove ignition sources, for example by earthing equipment so that static electricity cannot discharge as a spark. It can also limit the pressure rise by explosion venting or explosion suppression.<ref name="Z402" /> Deflagration pressure containment instead designs a vessel and its fittings to withstand the maximum pressure of an internal deflagration.<ref name="IS-F20" /> In the United States, Factory Mutual Data Sheet 7-32 (1993 edition) recommends at least one of four protections for process equipment that could explode: venting, enough strength to resist the overpressure, inerting or suppression.<ref name="IS-B27">Iqbal and Salley (2004), pp. B-27–B-28.</ref>

Inerting adds a gas such as nitrogen or carbon dioxide to reduce the oxygen concentration to a safe level, the highest of which is called the limiting oxidant concentration.<ref name="Z402" /><ref name="Z403" /> For the flammable gases and vapours listed by Zalosh, apart from hydrogen, this limit is 9.5 to 12 per cent oxygen by volume with nitrogen. With carbon dioxide it is 11.5 to 14.5 per cent, while hydrogen needs about 5 per cent with either gas.<ref name="Z403" /> In the United States, the National Fire Protection Association standard NFPA 69 (1997 edition) states that oxygen should be kept at least 2 percentage points below this limit under continuous monitoring. Without such monitoring a larger margin is needed.<ref name="Z403" /> Uneven mixtures and the accuracy and response time of oxygen monitors also have to be considered.<ref name="Z403" />

[[Explosion venting]] releases the combustion gases through openings during a deflagration, so that the pressure stays below the level that would damage the enclosure.<ref name="Z414">Zalosh (2002), p. 3-414.</ref> The openings are usually covered by blow-off panels, rupture discs or other vent devices, which usually open only after ignition. Venting works best when the vents open early, are as large as possible and let the gases escape freely. In the outside walls and roofs of buildings, the lowest practical opening pressure is usually just above the highest expected wind pressure, typically 0.96 to 1.44 kPa.<ref name="Z414" /> Explosion suppression instead detects an explosion in its first moments and discharges an extinguishing agent that quenches the flame.<ref name="Z417">Zalosh (2002), p. 3-417.</ref> It releases no flame or fuel, so it suits indoor equipment and toxic materials, but it is expensive to install and to reset.<ref name="Z417" />

Neither venting nor suppression can protect against a detonation. Vents open only after the explosion has started, while a detonation reaches its maximum pressure the instant its shock front arrives.<ref name="Z414" /><ref name="Z411" /> Venting guidelines are also limited because they are based on tests and do not account for the turbulence and equipment obstructions of a particular application.<ref name="Z416">Zalosh (2002), p. 3-416.</ref> Most of them also ignore how much of the enclosure is filled with the flammable mixture.<ref name="Z416" />
[[File:fse-explosion-v3.svg|thumb|upright=1.5|alt=Prevention, venting and containment are mapped to deflagration; venting is excluded for detonation.|Protection must match the explosion mechanism. Based on Zalosh (2002), pp. 3-411–3-416.]]

== Assessment and uncertainty ==

An explosion hazard evaluation usually has three steps. It recognises where a flammable fuel-air mixture could form, identifies ignition sources that could then be present, and works out the resulting pressures and possible structural damage.<ref name="Z402" /> In the chemical process industries, fire and explosion risk can also be assessed quantitatively, as a function of how often an event occurs and how severe its consequences are.<ref name="Barry-176">Barry (2002), p. 5-176.</ref> Such studies help to compare design options and to map explosion overpressure zones for emergency planning.<ref name="Barry-176" /> The amount of fuel in an accident depends on the release rate and duration, and so on how quickly a leak is detected and isolated.<ref name="Barry-182">Barry (2002), p. 5-182.</ref><ref name="Barry-184" />

Evaluations have to allow for uneven or layered mixtures of gas and air.<ref name="Z403" /> Zalosh gives the example of about 200 g of butane leaking from an aerosol can into a filling room of 4 by 4 by 3 m.<ref name="Z410" /> Spread evenly through the 48 m³ room, this gas would be too little to form a flammable mixture. If it mixes in the right proportion with only part of the air and is ignited, the pressure in the unvented room still rises by about 0.46 bar.<ref name="Z410" /> That is more than rooms in industrial buildings can withstand, so some form of explosion venting and suppression would be needed.<ref name="Z410" />

Several limits make explosion predictions uncertain, and NUREG-1805 notes that the pressures produced are usually difficult to predict.<ref name="IS-15-12" /> Dust explosions are harder to model than gas explosions.<ref name="Z414" /> Detailed computer models of gas explosions are too complex for routine vent design, but some are used for special cases such as congested offshore platform modules.<ref name="Z414" /> Laboratory results depend on the ignition source and on the turbulence in the test vessel at the moment of ignition.<ref name="Z404">Zalosh (2002), p. 3-404.</ref> A standard method for dust tests was therefore developed so that different laboratories obtain reproducible results.<ref name="Z409" /> Barry also reports that human factors, such as management controls and operator errors, account for about 70 to 85 per cent of the primary causes of fires and explosions in the process industries.<ref name="Barry-188">Barry (2002), p. 5-188.</ref>

== See also ==

* [[Fireball]]
* [[Flammability limits]]
* [[Hazardous area classification]]
* [[Premixed flame]]
* [[Thermal runaway]]
* [[TNT equivalence]]

== Notes ==

<references />

== References ==

* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-176–5-213). National Fire Protection Association; Society of Fire Protection Engineers.
* Beyler, C. L. (2002a). Fire hazard calculations for large, open hydrocarbon fires. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-268–3-314). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Simmons, R. F. (2002). Premixed burning. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 1-144–1-154). National Fire Protection Association; Society of Fire Protection Engineers.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Zalosh, R. (2002). Explosion protection. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-402–3-421). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Explosions & Industrial Fires]]

Hosereel

2026-11-02T18:09:50Z

Mark: Redirect to Hose reel (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Hose reel]]

Fire hose reel

2026-11-02T18:09:44Z

Mark: Redirect to Hose reel (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Hose reel]]

Fire investigation

2026-11-02T18:09:38Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, new sourced content, See also, links, style (revised by Claude Opus 5.5)

'''Fire investigation''' is the examination of a fire after the event to establish where and how it started, how it developed and how the building, its fire protection and its occupants were affected. Writing on spontaneous ignition in the SFPE Handbook, Gray notes that fire prevention and fire cause investigation both need to identify the critical conditions for ignition, before and after the event respectively.<ref name="Gray-2-211">Gray (2002), p. 2-211.</ref> Hall and Ahrens list the reconstruction of major fires among the engineering analyses that require input data on fires.<ref name="HA-5-65">Hall and Ahrens (2002), p. 5-65.</ref> The Society of Fire Protection Engineers likewise counts post-fire investigation and analysis as part of fire protection engineering.<ref name="IFEG-US-0.3-1">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-1–0.3-2.</ref>

Fire investigation matters because its findings explain why fires start and why protection succeeds or fails, and they can lead to changes in how buildings are designed, built and regulated. The US investigation of the World Trade Center disaster of 2001, for example, was meant to serve as the basis for improvements in building practice and revisions to codes and standards.<ref name="NIST-xxxv">National Institute of Standards and Technology (2005), p. xxxv.</ref> Investigations depend on the evidence that survives, and large fires destroy much of it. Fire loss statistics from many sources show an unknown cause more often in fires with multimillion-dollar losses than in smaller fires, probably because more evidence is lost.<ref name="Gray-2-211" />

== Purpose and scope ==

Investigations differ in purpose and authority. The US National Institute of Standards and Technology (NIST) investigated the World Trade Center disaster to determine why and how the buildings collapsed. It also asked why injuries and fatalities were high or low depending on location, and examined the procedures used in design, construction, operation and maintenance and the parts of codes and standards that warranted revision.<ref name="NIST-xxxv" /> NIST is a non-regulatory agency whose investigations focus on fact finding. It has no authority to find fault or negligence, and its reports may not be used in lawsuits for damages.<ref name="NIST-xxxv" />

Other investigations can have legal consequences. Van Rossum notes that an investigation after a fire disaster may show that the cause lies in demonstrably wrong advice, below the knowledge and skill that could be expected at the time. In that case the adviser can be prosecuted.<ref name="VR-2.5">Van Rossum (2027), §2.5.</ref>

Fire services also investigate routine fires. For the World Trade Center buildings, the New York City fire department provided NIST with 112 records of its Bureau of Fire Investigation from 1977 to 2001. It also provided 397 operational fire reports from 1970 to 2001, all on standardised forms. NIST's review of earlier fires included, for example, a fire on 14 February 1975 on the 11th floor of WTC 1, one of the two towers. It spread through unprotected floor openings in utility closets and caused damage from the 10th to the 19th floor.<ref name="Kuligowski-1">Kuligowski et al. (2005), p. 1.</ref>

Large investigations break the work into specific questions. For the sprinklers, standpipes and hoses of the towers, the NIST study first documented their design and installation and compared them with the codes and standards of record. It then estimated their capacity under normal conditions with hydraulic calculations.<ref name="Hopkins-xxxii">Hopkins et al. (2005), p. xxxii.</ref> Only then did it ask what happened to the systems at each major event, how their performance was affected and at what point in the sequence they were lost.<ref name="Hopkins-xliii">Hopkins et al. (2005), p. xliii.</ref>
[[File:fse-fire-investigation-v1.svg|thumb|upright=1.5|alt=Questions guide evidence collection, reconstruction, modelling and findings with uncertainty.|Fire investigation reconstructs events from evidence and explicit inference. Based on Hopkins, Schoenrock, and Budnick (2005), pp. xxxi–xxxii and Hall and Ahrens (2002), pp. 5-65–5-67.]]

== Evidence and how it is gathered ==

Fire investigators normally read the path and intensity of a fire from telltale signs left in the building. In the World Trade Center towers this was impossible because neither building remained, so NIST relied on what may have been the most photographed disaster in history.<ref name="Gann-xxxviii">Gann, Hamins, et al. (2005), p. xxxviii.</ref> In each photograph and video frame, every window was coded for fire, smoke and whether the window was still in place, which produced detailed timelines of fire spread.<ref name="Gann-xxxviii" /> NIST also reviewed tens of thousands of pages of documents, interviewed over a thousand people and analysed 236 pieces of steel recovered from the wreckage.<ref name="NIST-xxxvi">National Institute of Standards and Technology (2005), p. xxxvi.</ref>

Time links the evidence together. NIST describes time as the unifying factor in combining photographs, videos, survivor accounts, emergency calls and communications among emergency responders.<ref name="NIST-82">National Institute of Standards and Technology (2005), p. 82.</ref> Images were timed by matching them to one well-defined event, the impact of the second aircraft at 9:02:59 a.m., and then to other events visible in several images. In all, 3,032 photographs and 2,673 video clips were timed to within 3 seconds or better, and the uncertainty of each time was logged.<ref name="NIST-83">National Institute of Standards and Technology (2005), pp. 83–84.</ref>

Physical evidence needs careful interpretation. NIST found that the primer paint on the towers' steel cracked in a "mud cracking" pattern above 250 °C. Deformation and the environment can also cause such cracks, so their absence shows that the steel stayed below 250 °C, but their presence does not prove high temperature.<ref name="Gayle-94">Gayle et al. (2005), p. 94.</ref> The method could not tell whether the heating happened before or after the collapse. The panels examined were also only 3% of the perimeter columns on the fire floors and could not be treated as representative of the others.<ref name="Gayle-xli">Gayle et al. (2005), p. xli.</ref>

People are a source of evidence as well. For the evacuation of the towers, NIST gathered over 1,000 new interviews with survivors, over 700 published interviews, emergency calls and transcripts of emergency communications.<ref name="Averill-iii">Averill et al. (2005), p. iii.</ref> Proulx notes that fire victims may have difficulty reporting accurately how long they waited before starting to evacuate, but that interview techniques can give acceptable estimates.<ref name="Proulx-3-349">Proulx (2002), p. 3-349.</ref> The causes of death in fires have been studied through pathological investigations of fire victims.<ref name="Purser-2-85">Purser (2002), p. 2-85.</ref> Carbon monoxide combines with haemoglobin in the blood to form carboxyhaemoglobin. In the Strathclyde study of fire deaths in the United Kingdom, 54% of those who died had a lethal level of it, and 69% had a level capable of causing incapacitation.<ref name="Purser-2-100">Purser (2002), p. 2-100.</ref>

== Establishing the cause ==

To describe how a fire started, investigators separate the parts of the ignition sequence. US fire incident coding distinguishes the form of heat of ignition and the equipment involved, which together describe the [[ignition source]], from the form and type of material first ignited. It also records the ignition factor that brought heat and fuel together, and the area of origin.<ref name="HA-5-68">Hall and Ahrens (2002), p. 5-68.</ref> The New York fire department's structural fire form recorded the same kind of information, and it called the ignition factor the cause.<ref name="Kuligowski-2">Kuligowski et al. (2005), p. 2.</ref>

Some causes leave characteristic traces. Spontaneous ignition of stacked material, such as cotton, woodchips or oily rags, starts in the well-insulated centre of the pile. Such a pile can therefore be charred or burnt to ash inside while looking almost untouched outside.<ref name="Gray-2-212">Gray (2002), p. 2-212.</ref><ref name="Gray-2-224">Gray (2002), p. 2-224.</ref> Hot gases escape along the path of least resistance and form "chimneys" of charred material, and several chimneys are the norm. Gray reports that finding more than one heavily charred area has led to wrongful charges of arson, based on the myth that more than one seat of fire means the fire was started deliberately.<ref name="Gray-2-225">Gray (2002), p. 2-225.</ref>

Gray lists the practical factors that make spontaneous ignition more likely, including a large body of material, high surrounding temperatures, thermal insulation, porous or fibrous material and a high stacking temperature.<ref name="Gray-2-224" /> Material left undisturbed for longer than usual is also reason for suspicion. In one case a warehouse of cottonseed meal burned down after a transport strike had left the meal in place far longer than normal.<ref name="Gray-2-225" /> In another, an instant-noodle factory burned down after new management sped up the production line, so that the noodles were packed hotter than before. Laboratory tests and calculations then showed that the packed pallets could ignite spontaneously at the new temperatures but not at the old ones.<ref name="Gray-2-226">Gray (2002), pp. 2-225–2-226.</ref>

Gray advises caution about the timing of such fires without detailed knowledge of the initial conditions.<ref name="Gray-2-224" /> Whenever spontaneous ignition is suspected, Gray recommends excavating the material, with photographs and temperature probe records at all stages. He has measured temperatures as high as 200 °C in buried material more than two weeks after a fire was put out. Unburnt oily rags at the bottom of a bin do not rule out spontaneous ignition either.<ref name="Gray-2-225" />

== Reconstructing the fire ==

A reconstruction places the evidence in the sequence of the fire. Van Rossum divides a room fire into three phases. In the development phase, a local fire of one or a few objects grows until flashover. After flashover the fire is fully developed, and the decay phase can begin, for example, when the fuel runs out or the fire brigade intervenes. These [[fire development stages]] matter for interpretation, because an active suppression system normally acts during the development phase and so prevents the fire from becoming fully developed.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>

[[Fire dynamics]], defined in a US nuclear regulatory report as the scientific study of hostile fires, describes ignition, flame spread, fire growth, smoke movement and their effects in an enclosure.<ref name="Iqbal-1-1">Iqbal and Salley (2004), p. 1-1.</ref> Smoke rises under buoyancy to the upper part of the room of origin and leaves through openings, driven mainly by pressure differences. The International Fire Engineering Guidelines (2005 edition) note that hand calculations of its spread beyond the room of origin are more difficult and more uncertain than those within it.<ref name="IFEG-2.5-2">National Research Council of Canada et al. (2005), p. 2.5-2.</ref><ref name="IFEG-2.5-6">National Research Council of Canada et al. (2005), p. 2.5-6.</ref>

Tests can fill gaps in the evidence. NIST set out to characterise the type, mass and layout of the combustibles in the towers, the fire endurance of the partitions and the properties of the insulation on the steel.<ref name="Gann-2">Gann, Hamins, et al. (2005), p. 2.</ref> Its reconstruction relied heavily on computer simulation, because the premises could not be examined after the fire and eyewitness information was severely limited. To support the simulations, NIST burned six single office workstations, the dominant combustibles in the buildings, to learn how they may have burned and to improve its fire model.<ref name="Ohlemiller-iii">Ohlemiller et al. (2005), p. iii.</ref>

== Modelling and computational fluid dynamics ==

[[Computational fluid dynamics]] (CFD) studies the flow of gases and liquids by solving the flow equations numerically on a grid of cells. A CFD model can show smoke spread, gas temperatures and velocities, flows through openings and the time to flashover in three dimensions as they change over time.<ref name="VR-11.1">Van Rossum (2027), §11.1.</ref><ref name="VR-11.2">Van Rossum (2027), §11.2.</ref> Turbulent flows, which are typical of fires, can only be approximated. CFD therefore gives good qualitative insight, but its exact results must be interpreted carefully and critically.<ref name="VR-11.1" /> Zone models such as CFAST, released by NIST,<ref name="VR-9.5">Van Rossum (2027), §9.5.</ref> are also used internationally for fire safety design and post-fire reconstruction.<ref name="Peacock-3">Peacock et al. (2026), p. 3.</ref>

In the World Trade Center investigation, the unusual mix of available information led to a high reliance on computational tools, and NIST upgraded its CFD model, the Fire Dynamics Simulator, for the reconstruction.<ref name="Gann-2" /><ref name="Gann-4">Gann, Hamins, et al. (2005), p. 4.</ref> It varied the uncertain inputs to find those to which the results were most sensitive and those that agreed best with the photographs.<ref name="Gann-2-3">Gann, Hamins, et al. (2005), pp. 2–3.</ref> The accuracy of the predictions was judged by their consistency with the photographic evidence.<ref name="Gann-4" /> For each tower it ran a less severe and a more severe case, which gave some understanding of the uncertainty in the predictions.<ref name="NIST-81">National Institute of Standards and Technology (2005), pp. 81–82.</ref>
[[File:fse-fire-investigation-v3.svg|thumb|upright=1.5|alt=Two candidate scenarios are tested against observations and model limitations before conclusions.|Alternative reconstructions should be tested against evidence and sensitivity. Based on Notarianni (2002), pp. 5-43–5-44 and McGrattan et al. (2026), p. 107.]]

Models also have limits. NIST decided not to model smoke movement and survival conditions throughout the occupied parts of the towers. There was no quantitative information on conditions inside the towers and no verifiable information on damage between floors, so such simulations for the impact floors and above would have been grossly uncertain.<ref name="Gann-3">Gann, Hamins, et al. (2005), p. 3.</ref> The Fire Dynamics Simulator predicts the thermal environment of a fire, but it relies on empirical models for the activation of sprinklers and detectors.<ref name="FDS-107">McGrattan et al. (2026), p. 107.</ref> Smoke detector response is especially hard to model, because the production and transport of smoke early in a fire are not well understood.<ref name="FDS-108">McGrattan et al. (2026), p. 108.</ref> In forensic reconstructions, the amount of soot deposited on surfaces in a simulation can be correlated with what is observed after the fire.<ref name="FDS-87">McGrattan et al. (2026), p. 87.</ref>

== Evaluating protection systems ==

An investigation compares what a system could do with what it actually did. NIST found that the sprinkler and standpipe systems of the towers had for the most part exceeded the code requirements of their time, but the adverse effects of the aircraft impacts on them were extensive.<ref name="Hopkins-xlv">Hopkins et al. (2005), p. xlv.</ref> WTC 1 was the first tower to be struck.<ref name="Hopkins-xxxi">Hopkins et al. (2005), p. xxxi.</ref> Its estimated impact damage would probably have destroyed at least one standpipe riser and the sprinkler systems on the 94th to 96th floors, and cut the water supply to other systems after a limited time.<ref name="Hopkins-xliii" /><ref name="Hopkins-xliv">Hopkins et al. (2005), p. xliv.</ref> The collapse of WTC 2 damaged the city water mains near the site, and the collapse of WTC 1 probably caused significant further damage.<ref name="Hopkins-xliv" />
[[File:fse-fire-investigation-v2.svg|thumb|upright=1.5|alt=Pre-incident conditions, ignition, detection, fire growth and consequences, with fire, water-supply and occupant tracks.|An investigation must align system states with the incident timeline. Based on Hopkins, Schoenrock, and Budnick (2005), pp. xxxi–xlii and Van Rossum (2027), §4.11.]]

The evidence on systems is often incomplete. For the towers' suppression systems there was very little eyewitness or communications information. NIST therefore based its estimates on the incident information it had gathered, the likely effects of the impacts and historical performance records for sprinklers.<ref name="Hopkins-xxxi" /> Most of the New York fire department's reports of significant earlier fires documented the performance of detectors and sprinklers, but almost all lacked information on the smoke purge system.<ref name="Kuligowski-2" />

Which sprinklers opened, and when, also needs careful reading. Water droplets carried by the hot gas flow under the ceiling from the first sprinklers can cool the heat-sensitive links of sprinklers further away and delay their opening. Cooper calls this random effect sprinkler skipping, and fusible-link vents can be delayed in the same way.<ref name="Cooper-3-239">Cooper (2002b), p. 3-239.</ref> Evidence from victims has comparable limits. Carboxyhaemoglobin is routinely measured in the blood of fire victims, but blood cyanide often is not, and post-fire cyanide levels are hard to relate to the exposure during the fire.<ref name="Purser-2-100" /><ref name="Purser-2-103">Purser (2002), p. 2-103.</ref>

== Limits and use of findings ==

Investigators often work with fragmented information. NIST confirmed significant events from more than one source where possible, but this could not always be done, and it included events that it judged likely or probable from the accumulated information.<ref name="Hopkins-xxxi" /> Records can also be lost. The Port Authority of New York and New Jersey kept records of all significant fire events in the World Trade Center buildings, and these were lost in the collapse of the towers.<ref name="Kuligowski-1" /> Physical evidence may cover only a small and unrepresentative part of a building, as the recovered steel did.<ref name="Gayle-xli" />

A single investigation describes one event. Hall and Ahrens note that detailed accounts, including NFPA's reports of fire investigations, show the range and diversity of fires that can happen. Such anecdotes cannot be used to estimate incident rates or probabilities.<ref name="HA-5-70">Hall and Ahrens (2002), p. 5-70.</ref> Valid analysis of incident rates instead requires a statistically representative database of [[fire statistics]].<ref name="HA-5-69">Hall and Ahrens (2002), p. 5-69.</ref>

Collected investigation data can in turn feed design values. Holborn and colleagues analysed data from fire investigations in the Greater London area between 1996 and 2000 to derive fire sizes, fire growth rates and the times between events. The Australian data sheets for the Fire Safety Verification Method (print version 1.1, 2020) use their results for characteristic fire growth rates and for the share of fires that become fully developed.<ref name="Holborn-2004">Holborn et al. (2004), as cited in Australian Building Codes Board (2020a), Data Sheet B2, pp. 4–7.</ref> The World Trade Center investigation itself ended with 30 recommendations, covering structural integrity, fire endurance, active fire protection, evacuation, emergency response, procedures and practices, and education and training.<ref name="NIST-xiii">National Institute of Standards and Technology (2005), p. xiii.</ref>

== See also ==

* [[Firefighting]]
* [[Dry and wet risers]]
* [[Fire hydrant]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Averill, J. D., Mileti, D. S., Peacock, R. D., Kuligowski, E. D., Groner, N., Proulx, G., Reneke, P. A., & Nelson, H. E. (2005). ''Occupant behavior, egress, and emergency communications'' (NIST NCSTAR 1-7). National Institute of Standards and Technology.
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Gann, R. G., Hamins, A., McGrattan, K. B., Mulholland, G. W., Nelson, H. E., Ohlemiller, T. J., Pitts, W. M., & Prasad, K. R. (2005). ''Reconstruction of the fires in the World Trade Center towers'' (NIST NCSTAR 1-5). National Institute of Standards and Technology.
* Gayle, F. W., Fields, R. J., Luecke, W. E., Banovic, S. W., Foecke, T., McCowan, C. N., Siewert, T. A., & McColskey, J. D. (2005). ''Mechanical and metallurgical analysis of structural steel'' (NIST NCSTAR 1-3). National Institute of Standards and Technology.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-211–2-228). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Kuligowski, E. D., Evans, D. D., & Peacock, R. D. (2005). ''Post-construction fires prior to September 11, 2001'' (NIST NCSTAR 1-4A). National Institute of Standards and Technology.
* McGrattan, K., Hostikka, S., Floyd, J., McDermott, R., Vanella, M., Mueller, E., & Paul, C. (2026). ''Fire Dynamics Simulator technical reference guide: Vol. 1. Mathematical model'' (6th ed., NIST Special Publication 1018-1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.1018
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Ohlemiller, T. J., Mulholland, G. W., Maranghides, A., Filliben, J. J., & Gann, R. G. (2005). ''Fire tests of single office workstations'' (NIST NCSTAR 1-5C). National Institute of Standards and Technology.
* Peacock, R. D., McGrattan, K. B., Forney, G. P., & Reneke, P. A. (2026). ''CFAST – Consolidated Fire and Smoke Transport: Vol. 1. Technical reference guide'' (Version 7, NIST Technical Note 1889v1). National Institute of Standards and Technology. https://doi.org/10.6028/NIST.TN.1889v1
* Proulx, G. (2002). Movement of people: The evacuation timing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-342–3-366). National Fire Protection Association; Society of Fire Protection Engineers.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-83–2-171). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Hose reel

2026-11-02T18:09:31Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, new sources, See also, links, style (revised by Claude Opus 5.5)

A '''hose reel''' is a fire hose kept permanently connected to the water supply of a building, so that trained occupants or employees can fight a fire before the fire department arrives.<ref name="IS-F62">Iqbal and Salley (2004), p. F-62.</ref><ref name="IS-F61">Iqbal and Salley (2004), p. F-61.</ref> The glossary of NUREG-1805 defines a related term, the small hose system, as hose of 5/8 in. to 1½ in. (about 16 to 38 mm) diameter for the use of employees, intended to control and extinguish fires in their earliest stage.<ref name="IS-F50">Iqbal and Salley (2004), p. F-50.</ref> The International Fire Engineering Guidelines name hose reels, together with fire extinguishers, as the means by which building occupants may suppress a fire.<ref name="IFEG-1.7-1">National Research Council of Canada et al. (2005), pp. 1.7-1–1.7-2.</ref> In high-rise buildings, such hoses may hang on the standpipes, which also provide connections for the hoses that firefighters carry in.<ref name="Evans-9">Evans et al. (2005), p. 9.</ref>

Rules for hose reels differ between countries and documents. In the United States, NFPA 14 provides Class II hose stations with 38 mm (1½ in.) hose for trained occupants, designed for about 380 L/min (100 gal/min), as summarised by NIST.<ref name="Hopkins-20">Hopkins et al. (2005), p. 20.</ref> The New York City Building Code required occupant hose reels and, for that reason, had no requirements for fire extinguishers.<ref name="Lew-151">Lew et al. (2005), p. 151.</ref> Their value depends on the user: fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they belong to a trained emergency crew.<ref name="IFEG-1.7-7">National Research Council of Canada et al. (2005), p. 1.7-7.</ref> Water also does not suit every fire, and NUREG-1805 warns never to use it on burning metals.<ref name="IS-B16">Iqbal and Salley (2004), p. B-16.</ref>

== Definition and terminology ==

The glossary of NUREG-1805, a report of the US Nuclear Regulatory Commission, uses several related terms. A small hose system is hose of 5/8 in. to 1½ in. diameter for the use of employees, intended to control and extinguish incipient fires.<ref name="IS-F50" /> An incipient fire is one that can still be controlled with portable extinguishers, Class II standpipes or small hose systems, without protective clothing or breathing apparatus.<ref name="IS-F38">Iqbal and Salley (2004), p. F-38.</ref> A standpipe hose cabinet holds standpipe outlets or stored fire hose, and the hoses are usually pre-connected and kept in a rack with release pins.<ref name="IS-F61" /> The list of abbreviations in the same report uses FHR for fire hose reel.<ref name="IS-G4">Iqbal and Salley (2004), p. G-4.</ref>

Many high-rise and other large buildings have an internal system of water mains, the standpipes, connected to fire hose stations; these pipes are covered under [[Dry and wet risers]].<ref name="IS-F62" /> In the World Trade Center (WTC) towers in New York, hoses pre-connected to the standpipes in the stairwells were installed for trained occupants. The same standpipes offered hose connections for the fire department on every floor.<ref name="Evans-xxix">Evans et al. (2005), p. xxix.</ref> For WTC 7, the NIST investigation describes hose reels in the stair enclosures and hose cabinets throughout the floors.<ref name="Hopkins-128">Hopkins et al. (2005), p. 128.</ref> A hose reel is not the same as a fire hydrant, which supplies water to fire department pumpers.<ref name="IS-F26">Iqbal and Salley (2004), p. F-26.</ref> Nor is it a fire department connection, through which the fire department pumps water from its trucks into a building system.<ref name="IS-F25">Iqbal and Salley (2004), p. F-25.</ref>

== Components and layout ==

In the WTC towers, a typical hose rack started with a 64 mm (2½ in.) standpipe valve and a reducer to 38 mm (1½ in.). A rack or cabinet then held 38 m (125 ft) of fire hose with a nozzle.<ref name="Hopkins-40">Hopkins et al. (2005), p. 40.</ref> The racks were mounted about 1.4 m (4½ ft) above the stair landing. This arrangement let the fire department or a fire brigade start manual firefighting with the smaller hose without carrying hoses up from the ground floor.<ref name="Hopkins-40" /> Such a station was provided on every floor of every stair. Extra hose cabinets were added so that the whole building lay within 7.6 m (25 ft) of the end of a hose nozzle.<ref name="Hopkins-127">Hopkins et al. (2005), p. 127.</ref>
[[File:fse-hose-reel-v1.svg|thumb|upright=1.5|alt=Water supply passes through a valve and hose to a nozzle aimed at the fire.|A hose reel works as a connected assembly, not as an isolated fitting. Based on Iqbal and Salley (2004), pp. F-61–F-62.]]

The 1968 Building Code of the City of New York was used for the design of WTC 1 and 2. It required standpipes to be placed so that a 6.1 m (20 ft) stream from a nozzle on at most 38 m (125 ft) of hose could reach every point of every floor.<ref name="GJ-29">Grill and Johnson (2005b), p. 29.</ref> Hose stations had to stand at the standpipe risers, inside or next to the entrances of the stair enclosures.<ref name="GJ-30">Grill and Johnson (2005b), p. 30.</ref> In the occupancy groups that included the business use of the towers, the hose was 1½ in. unlined linen hose, and auxiliary hose stations with the same hose were allowed.<ref name="GJ-2">Grill and Johnson (2005b), p. 2.</ref><ref name="GJ-30" /> Water had to be available at every hose outlet at all times, or be made available automatically when a hose valve was opened.<ref name="GJ-30" />

Under NFPA 14, as summarised by NIST, Class II hose stations are spaced so that every area lies within 6.1 m (20 ft) of the nozzle of a 30 m (100 ft) hose.<ref name="Hopkins-20" /> These stations provide small streams for trained occupants or fire brigades to fight incipient fires and to finish off afterwards. Class I systems instead have 64 mm valves that supply heavy streams for the fire department in advanced fires, and Class III systems combine both.<ref name="Hopkins-20" />

== Water supply, flow and pressure ==

A hose reel is only as good as its [[fire water supply]]. Wet standpipes, the preferred arrangement, are filled with water at all times and connected to an automatic supply such as the city mains, a tank with a pump, or an elevated tank.<ref name="Hopkins-21">Hopkins et al. (2005), p. 21.</ref> Manual dry standpipes have only fire department connections and no automatic supply.<ref name="Hopkins-21" /> In NUREG-1805, a manual standpipe relies on the fire service to supply it, and a semi-automatic standpipe needs a control device to be activated before water reaches the hose outlets.<ref name="IS-F61" />

The flows are modest compared with those for the fire service. NFPA 14, as summarised by NIST, designs Class II systems for about 380 L/min (100 gal/min) at about 450 kPa (65 psi) at the most demanding standpipe.<ref name="Hopkins-20" /> Class I and III systems are designed for about 1,900 L/min (500 gal/min) at about 690 kPa (100 psi).<ref name="Hopkins-20" /> In New York, pressure-reducing valves at 1½ in. hose stations were to limit the pressure to about 590 kPa (85 psi) at a flow of about 265 L/min (70 gal/min).<ref name="Hopkins-148">Hopkins et al. (2005), p. 148.</ref> In the WTC towers, tanks of about 19 m³ (5,000 gal) could supply about 1,900 L/min (500 gal/min) for 10 minutes, so that manual firefighting could begin before the manual fire pumps were started.<ref name="Hopkins-39">Hopkins et al. (2005), p. 39.</ref>

Hose reels usually share their supply with other systems. In WTC 7, the hose connections were supplied from combined sprinkler and standpipe systems, so they had the same supply zones as the sprinklers.<ref name="Hopkins-149">Hopkins et al. (2005), p. 149.</ref> For the lowest 20 floors, a loss of power to the automatic fire pump or significant damage to the city main could interrupt that supply.<ref name="Hopkins-xli">Hopkins et al. (2005), p. xli.</ref> According to NUREG/CR-6850, a rupture of the firefighting water main in a US nuclear power plant could make all water-based suppression, including manual hose stations, unavailable until the break is isolated.<ref name="Nowlen-13-3">Nowlen et al. (2005b), p. 13-3.</ref> Several outlets on one supply also compete for water. In NIST's calculations, four hose valves at the top of a WTC tower needed three or four fire pumps, while two pumps could supply only one.<ref name="Hopkins-148" />
[[File:fse-hose-reel-v2.svg|thumb|upright=1.5|alt=One riser and pump supply several hose reels, with an independent backup path.|Shared infrastructure can disable multiple hose outlets at once. Based on Hopkins et al. (2005), pp. xli and 149 and Nowlen et al. (2005b), p. 13-3.]]

== How water puts out a fire ==

A fire needs fuel, oxygen and enough heat, the three sides of the fire triangle described in ''Introduction to Fire Safety Engineering''.<ref name="VR-4.2">Van Rossum (2027), §4.2.</ref> Water from a hose acts on this triangle in several ways at once. When it reaches a burning solid, it cools the fuel, which then releases less flammable gas. It also cools the flames, so that they feed less heat back to the fuel.<ref name="IS-B15">Iqbal and Salley (2004), p. B-15.</ref> The steam it forms may keep oxygen away from the fire in some confined conditions, and a water fog may block heat radiation.<ref name="IS-B15" />

Water is the most commonly used extinguishing agent, mainly because it is widely available and cheap, and because it has a high specific heat and a high latent heat of evaporation.<ref name="Fleming-72">Fleming (2002), p. 4-72.</ref> The specific heat of water, 4,186 J/(kg·K), is about four times that of air, and turning water into steam takes extra energy on top of that.<ref name="VR-3.4">Van Rossum (2027), §3.4.</ref> Fleming gives 9,280 Btu for one US gallon of water heated from a room temperature of 21 °C until it has turned into steam at 100 °C. That is about 2.6 MJ per litre.<ref name="Fleming-72" />

A fire at the Point Beach nuclear plant in the United States in 2001 shows how little water a small fire can need. The fire brigade first discharged about 32 kg (70 lb) of dry chemical from three portable extinguishers without putting the fire out.<ref name="IS-H29">Iqbal and Salley (2004), p. H-29.</ref> It then extinguished the fire easily with a hose line, using 57 to 76 L (15 to 20 gal) of water.<ref name="IS-H29" /><ref name="IS-H30">Iqbal and Salley (2004), p. H-30.</ref> The dry chemical had covered large areas with white dust, whereas the small quantity of water left little to clean up.<ref name="IS-H29" /><ref name="IS-H30" />

== Fires for which water is unsuitable ==

Water does not suit every fire. In the table of fire classes in NUREG-1805, water is listed for Class A fires in ordinary combustibles such as wood, cloth, paper, rubber and many plastics.<ref name="IS-B16" /> It is not listed for flammable liquids and gases, for energised electrical equipment or for cooking oils and fats. Water and water-based extinguishers should never be used on Class D fires in combustible metals such as magnesium, sodium or lithium.<ref name="IS-B16" />

Liquids need special care. A burning liquid that is lighter than water and does not mix with it simply floats on the water and keeps burning.<ref name="IS-B58">Iqbal and Salley (2004), p. B-58.</ref> Water applied to a burning oil or fat far above the boiling point of water turns to steam below the surface. The steam can throw out the oil in an eruption that spreads the fire.<ref name="IS-B58" /> Some materials react with water and can produce heat, flammable or toxic gases or explosions, although enough water can overcome small amounts of such materials.<ref name="Fleming-72" />
[[File:fse-hose-reel-v3.svg|thumb|upright=1.5|alt=Trained responder deploys hose past obstructions and checks water-compatible fuel and egress.|Hose deployment requires access, training and a suitable fire scenario. Based on Evans et al. (2005), p. 9 and Iqbal and Salley (2004), pp. B-16 and B-58.]]

== Who uses a hose reel ==

Hose reels are meant for [[firefighting]] by trained occupants and staff in the first stage of a fire, although firefighters can use them too. In NUREG-1805, trained occupants or employees operate the hoses until the fire department arrives, after which firefighters can connect their own hoses to outlets near the fire.<ref name="IS-F62" /> NIST notes that the safe and effective use of pre-connected hoses requires training.<ref name="Evans-9" /> In the WTC towers, each hose station was intended for a trained fire brigade or the New York City fire department.<ref name="Hopkins-xxxiv">Hopkins et al. (2005), p. xxxiv.</ref> At the Waterford 3 nuclear plant in 1985, the fire brigade used a local hose station and water streams to put out a feedwater pump fire in about 10 minutes.<ref name="IS-H13">Iqbal and Salley (2004), p. H-13.</ref>

How far a design may rely on occupants is uncertain. NIST describes a long-standing debate about relying on occupants to use pre-connected hoses, and notes that some jurisdictions allow only Class I standpipes, for fire department use.<ref name="Hopkins-21" /> The International Fire Engineering Guidelines state that fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they belong to a specially trained site emergency crew.<ref name="IFEG-1.7-7" /> If there is good reason to expect effective firefighting by occupants, the analysis may include it, together with the time at which it starts.<ref name="IFEG-1.7-7" /> Its effect on the design fire is then taken as no effect, control or extinguishment.<ref name="IFEG-1.7-4">National Research Council of Canada et al. (2005), p. 1.7-4.</ref>

Research on human behaviour helps to explain this caution. In the SFPE Handbook, Bryan describes how a person who has recognised a fire decides between leaving the building and fighting the fire, for example with an extinguisher.<ref name="Bryan-318">Bryan (2002), p. 3-318.</ref> People in a familiar role and familiar surroundings, such as those with firefighting training, are likely to choose more suitable actions.<ref name="Bryan-319">Bryan (2002), p. 3-319.</ref> In a study of an office building fire in Osaka, the regular occupants fought the fire and alerted others, while people attending training sessions there, who did not know the building, mainly evacuated.<ref name="Horiuchi">Horiuchi et al. (1986), as cited in Bryan (2002), pp. 3-319 and 3-340.</ref>

== Hose reels, extinguishers and sprinklers ==

The International Fire Engineering Guidelines treat hose reels and [[fire extinguisher]]s alike, as means of suppression by occupants within the detection, warning and suppression sub-system.<ref name="IFEG-1.7-1" /><ref name="IFEG-1.2-10">National Research Council of Canada et al. (2005), p. 1.2-10.</ref> Building codes do not always require both. NIST found that the New York City Building Code had no requirements for fire extinguishers, because it required occupant hose reels instead.<ref name="Lew-151" /> The Port Authority's design guidelines for the WTC nevertheless required portable extinguishers in all spaces, under a fire department directive and the New York City Fire Prevention Code.<ref name="GJc-17">Grill and Johnson (2005c), p. 17.</ref> For battery rooms in US nuclear power plants, NRC Regulatory Guide 1.189, as summarised in NUREG-1805, says that a hose station and portable extinguishers should be readily available outside the room.<ref name="IS-16-6">Iqbal and Salley (2004), p. 16-6.</ref>

Hose reels are not a substitute for automatic sprinklers, and NIST notes that standpipe systems are not considered an alternative to automatic fire suppression.<ref name="Hopkins-21" /> NUREG-1805 explains that sprinklers typically use less water than fire hoses. The human response, from discovering the fire to the arrival of a fire brigade, usually takes much longer than sprinklers need to control a fire in its early stage.<ref name="IS-10-1">Iqbal and Salley (2004), p. 10-1.</ref> Even in a sprinklered building, people with extinguishers or hose lines are generally needed to put out all the burning, especially where the fire is shielded from the sprinkler spray.<ref name="Evans-9" />

In Australian performance-based design, firefighting by occupants is usually left out of the design fire. The handbook for the Fire Safety Verification Method notes that many smouldering and small flaming fires are dealt with by the occupants and therefore go unreported.<ref name="ABCB-61">Australian Building Codes Board (2020b), pp. 61–62.</ref> It is common practice to consider reported fires only and to ignore suppression by occupants.<ref name="ABCB-61" /> For the risk of a major structural collapse, the handbook suggests deriving the frequency of fires that occupants could not manage from fire statistics.<ref name="ABCB-92">Australian Building Codes Board (2020b), p. 92.</ref>

== Reliability and maintenance ==

A hose reel can fail anywhere between the water source and the nozzle. For sprinkler systems, NUREG-1805 lists causes of water supply failure such as a closed water supply valve, a broken supply header, an empty water tank and a fire pump that does not start.<ref name="IS-10-2">Iqbal and Salley (2004), p. 10-2.</ref> Where hose stations share that supply, as they did in WTC 7, the same faults would affect them.<ref name="Hopkins-149" /> For US nuclear power plants, NUREG/CR-6850 asks whether hose stations would survive an earthquake, whether an alternative source of firefighting water exists and whether there is enough hose to use it.<ref name="Nowlen-13-7">Nowlen et al. (2005b), pp. 13-7–13-8.</ref> Where a water hose reel is credited, the analyst also checks that vulnerable components are shielded from water spray and that drainage is adequate. Floor penetrations must be verified as sealed, so that firefighting water cannot run into the compartment below.<ref name="Nowlen-11-18">Nowlen et al. (2005b), p. 11-18.</ref>

Performance records are not kept for standpipe and pre-connected hose systems, and NIST found their performance difficult to assess.<ref name="Hopkins-21" /><ref name="Hopkins-xlii">Hopkins et al. (2005), p. xlii.</ref> At the WTC, these systems met the New York City Building Code but not the flow rates and durations of NFPA 14.<ref name="Evans-xxxi">Evans et al. (2005), p. xxxi.</ref> The International Fire Engineering Guidelines ask that active fire protection equipment be maintained in line with the relevant codes, standards and manufacturer's literature, in some jurisdictions through essential safety provisions.<ref name="IFEG-1.7-8">National Research Council of Canada et al. (2005), p. 1.7-8.</ref> Among the American standards, NUREG-1805 lists NFPA 1962 (2003 edition) on the inspection, care and use of fire hose, couplings and nozzles and the service testing of fire hose.<ref name="IS-E12">Iqbal and Salley (2004), p. E-12.</ref>

== See also ==

* [[Fire hydrant]]
* [[Fire classes]]
* [[Fire service access]]
* [[Firefighting lift]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Grill, R. A., & Johnson, D. A. (2005b). ''Fire protection and life safety provisions applied to the design and construction of WTC 1, 2, and 7 and post-construction provisions applied after occupancy'' (NIST NCSTAR 1-1D). National Institute of Standards and Technology.
* Grill, R. A., & Johnson, D. A. (2005c). ''Post-construction modifications to fire protection and life safety systems of the World Trade Center towers'' (NIST NCSTAR 1-1H). National Institute of Standards and Technology.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Secondary explosion

2026-11-02T18:09:25Z

Mark: Redirect to Dust explosion (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Dust explosion]]

Secondary dust explosion

2026-11-02T18:09:19Z

Mark: Redirect to Dust explosion (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Dust explosion]]

Dust deflagration

2026-11-02T18:09:13Z

Mark: Redirect to Dust explosion (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Dust explosion]]

Dust explosions

2026-11-02T18:09:07Z

Mark: Redirect to Dust explosion (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Dust explosion]]

Dust explosion

2026-11-02T18:08:46Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, added sources, structure, links, See also, style (revised by Claude Opus 5.5)

A '''dust explosion''' is an [[explosion]] of a cloud of combustible dust or powder suspended in air. Once the cloud is ignited, flame spreads through it, and in a confined space the hot combustion gases cannot expand freely, so the pressure rises rapidly.<ref name="Z402">Zalosh (2002), p. 3-402.</ref><ref name="Z403">Zalosh (2002), p. 3-403.</ref> Dusts known to explode include food powders such as sugar, corn starch and milk powder, as well as coal, plastics and metal powders such as aluminium.<ref name="Z404">Zalosh (2002), p. 3-404.</ref> In closed test vessels, twenty representative dusts reached maximum pressures of 6.7 to 11.2 bar above atmospheric pressure, about the same range as flammable gases.<ref name="Z407">Zalosh (2002), p. 3-407.</ref>

The cloud can be ignited by sparks, static electricity, hot surfaces or dust deposits that heat up by themselves.<ref name="Z405">Zalosh (2002), p. 3-405.</ref><ref name="IS-15-3">Iqbal and Salley (2004), p. 15-3.</ref> A first explosion inside equipment can also lift settled dust into a new cloud, and the resulting secondary explosion in an occupied building can cause many casualties.<ref name="Z409-410">Zalosh (2002), pp. 3-409–3-410.</ref> Protection relies on avoiding explosive clouds, removing ignition sources, inerting, and limiting the pressure by venting, suppression or an enclosure strong enough to resist it.<ref name="Z402" /><ref name="IS-F20">Iqbal and Salley (2004), p. F-20.</ref>

== How a dust cloud burns ==

A dust explosion first needs a cloud, and some disturbance or air movement is always needed to raise dust into the air.<ref name="Z409">Zalosh (2002), p. 3-409.</ref> Once the cloud is ignited, flame travels through the mixture of dust and air. In an enclosure the confinement stops the hot combustion products from expanding freely.<ref name="Z402" /> Ignition of a dust cloud in an unvented enclosure usually produces a deflagration, a flame that moves away from the ignition point slower than sound.<ref name="Z406">Zalosh (2002), p. 3-406.</ref> For dust as for gas, the pressure reached depends on how far the flame has spread and on the temperature and composition of the burned gas.<ref name="Z406" /> NUREG-1805, a fire hazard analysis guide of the US Nuclear Regulatory Commission, lists dust explosions among the combustion explosions, together with gas, mist and backdraft explosions.<ref name="IS-15-2">Iqbal and Salley (2004), p. 15-2.</ref>
[[File:fse-dust-explosion-v1.svg|thumb|upright=1.5|alt=Air movement suspends dust, ignition propagates flame and confinement raises pressure.|A dust explosion requires dispersion, ignition and flame propagation. Based on Zalosh (2002), pp. 3-402–3-406.]]

For organic dusts, the particles have to give off flammable vapour first, and the flame then burns in the gas phase.<ref name="Beyler-182">Beyler (2002b), p. 2-182.</ref><ref name="Beyler-183">Beyler (2002b), p. 2-183.</ref> This need to turn the fuel into vapour is why the lower flammable limit of a dust is expected to be higher than that of a comparable gas.<ref name="Beyler-182" /> For very small particles the limit no longer depends on particle size and comes close to that of the matching gas, provided all of the fuel turns into vapour.<ref name="Beyler-182" /> Metal and graphite dusts are different, because for them burning on the surface of the particles plays an important part in spreading the flame.<ref name="Beyler-183" />

Turbulence has an even larger effect on the rate of pressure rise in dust explosions than in gas explosions, because some motion is always needed to raise the cloud.<ref name="Z409" /> Dust particles also take a finite time to burn, which gives a dust flame a finite thickness.<ref name="Z409" /> A mixture of a combustible gas with a combustible dust is called a hybrid mixture. Explosion venting is used for such mixtures as well as for gases, dusts and mists.<ref name="IS-F37">Iqbal and Salley (2004), p. F-37.</ref><ref name="Z414">Zalosh (2002), p. 3-414.</ref> When fire spreads rapidly through a dust cloud without producing damaging pressure, the event is called a flash fire.<ref name="IS-F32">Iqbal and Salley (2004), p. F-32.</ref>

== When dust can explode ==

Not every dust cloud can explode. Combustible dusts and powders pose an explosion hazard when their typical particle size is below 100 to 400 micrometres, depending on how combustible the material is.<ref name="Z403" /> The concentration must also lie between the lower and upper explosive limits. For dusts finer than about 100 micrometres the lower limit is typically 30 to 60 g/m³, roughly the same as for many flammable gases in these units.<ref name="Z403" /> The upper limit is typically 2,000 to 6,000 g/m³, but it is difficult to measure and even more difficult to use as a means of prevention.<ref name="Z403" /> In Zalosh's table of representative dusts, mostly tested in a 1 m³ vessel, the minimum explosible concentration ranges from 15 g/m³ for naphthalene and phenolic resin to 250 g/m³ for zinc.<ref name="Z404" />

Smaller particles generally lower the minimum explosible concentration, until a limiting size is reached below which it falls no further.<ref name="Z404" /> Above that size, burning appears to be limited by how fast the particles give off vapour, which depends on their surface area. Below it, the chemistry of the gas flame seems to set the limit.<ref name="Z404" /> For a given material and particle size, the minimum explosible concentration falls steadily as the temperature rises.<ref name="Z404" /> For bituminous coal the lower limit stays well above the 48 g/m³ typical of gaseous hydrocarbons, because not all of the coal turns into vapour. It is not expected to fall below 50 g/m³ even in pure oxygen.<ref name="Beyler-182" />

The most violent explosions do not occur at the lower limit. The concentration that gives the highest pressure is often about 500 g/m³. For many organic materials this is roughly twice the amount needed for complete burning and five to ten times the minimum explosible concentration.<ref name="Z407" />

Concentrations in real plants are often unknown or deceptively low. In a plastic powder silo, for example, concentrations can become much higher than those measured during normal filling and emptying. This can happen when vibration or air blasts are used to free blocked powder.<ref name="Z404" /> A worked example compares two coal mills. The dust leaving one mill, at 0.27 kg/m³, is well inside the explosive range. The other, at 1.96 kg/m³, is close to the upper limit of 2 to 4 kg/m³ reported for coal.<ref name="Z405" />

== Ignition sources ==

The [[minimum ignition energy]] of a dust cloud is measured with an electric spark in a 1.2-litre tube, sometimes called a modified Hartmann tube.<ref name="Z405" /> For the dusts in Zalosh's table with measured values, it ranges from less than 1 mJ to more than 2,000 mJ.<ref name="Z405" /> NUREG-1805 states that a dust cloud may ignite with as little as 20 mJ, compared with 0.3 mJ for a flammable gas or vapour.<ref name="IS-C1">Iqbal and Salley (2004), p. C-1.</ref> Several dusts in Zalosh's table need even less, such as sugar at 14 mJ and naphthalene at less than 1 mJ.<ref name="Z404" /> Longer sparks ignite dust more easily: adding inductance or resistance to the circuit can lower the minimum ignition energy tenfold. An electrostatic discharge therefore needs more energy to ignite a dust cloud than a spark from an electrical switch.<ref name="Z405" />

Static electricity is a real hazard in powder handling. In a worked example, a poorly earthed silo would have to reach about 14 kV before its spark could ignite a powder needing 50 mJ from a capacitive discharge. Friction and impact of the powder during filling and emptying can produce such voltages.<ref name="Z405" /> Earthing the silo prevents charge from building up on the silo itself. Charge can still collect, however, on ungrounded objects inside it and possibly on powder with a high electrical resistance.<ref name="Z405-406">Zalosh (2002), pp. 3-405–3-406.</ref>

Hot surfaces are a second group of ignition sources. The minimum ignition temperature of a dust cloud is measured by blowing dust through a heated vertical tube. Most dusts in Zalosh's table ignite between 440 °C and 750 °C.<ref name="Z404" /> A dust layer 5 mm thick on a hot plate often ignites at a significantly lower temperature, because a layer loses heat less easily than a cloud.<ref name="Z404" /><ref name="Z405" /> Siwek and Cesana's data suggest that a hot spot of at least 900 °C, for example from friction in a mill, can ignite a cloud with an ignition temperature below 600 °C.<ref name="SC">Siwek and Cesana (1995), as cited in Zalosh (2002), p. 3-405.</ref> Sparks from friction and impact, by contrast, only ignite dusts with a minimum ignition energy below 10 mJ and an ignition temperature below 500 °C.<ref name="SC" />

Dust can also ignite itself. Deposits on hot process surfaces can undergo accelerated self-heating and eventually ignite.<ref name="IS-15-3" /> In a milk-drying plant, the air entering a spray dryer was heated to 200 °C, and surfaces near the inlet might reach this temperature too. Powder collecting on such hot surfaces could ignite spontaneously and then act as the ignition source for a dust explosion. Such explosions have occurred in milk-drying plants with devastating consequences.<ref name="Beever">Beever (1988), as cited in Gray (2002), p. 2-226.</ref> Smouldering in grain silos is a related problem, and it must be completely extinguished before a silo is emptied, to avoid the possibility of a dust explosion.<ref name="Ohlemiller">Ohlemiller (2002), p. 2-207.</ref>

== Explosion pressure and the deflagration index ==

In standard closed-vessel tests, the maximum pressures of the twenty dusts in Zalosh's table range from 6.7 bar for zinc to 11.2 bar for aluminium.<ref name="Z404" /> For three of the four dusts in one test series, the maximum pressure did not change as long as the median particle size was no more than 100 micrometres.<ref name="Z407" /> Polyvinyl chloride (PVC) dust, which is significantly less combustible than the other three, gave lower pressures above 20 micrometres and could not be ignited at all from 150 micrometres.<ref name="Z407" />

The rate of pressure rise matters for protection, because the vent area needed depends on it as well as on the size of the enclosure.<ref name="Z414" /> The rate of pressure rise depends mainly on how fast the flame spreads, on the size of the vessel and on the flame temperature.<ref name="Z407" /> The maximum rate of pressure rise measured in a closed vessel, scaled by the size of the vessel, is expressed as the [[deflagration index]], KSt, in bar·m/s.<ref name="Z409" />

Some venting models use the index to represent how fast a dust burns.<ref name="Z414" /> In the vent sizing equation proposed for the 2002 edition of NFPA 68, the US venting guide of the National Fire Protection Association, the vent area increases in proportion to KSt.<ref name="Z416">Zalosh (2002), p. 3-416.</ref><ref name="Z417">Zalosh (2002), p. 3-417.</ref> In Zalosh's table, aluminium has the highest value at 515 bar·m/s. The other dusts lie between 28 and 209 bar·m/s, with corn starch at 128 and coal at 59.<ref name="Z404" />

The turbulence in a test vessel is highest when the dust is first blown in and decays by the time the whole cloud has entered. The delay between dust injection and ignition therefore changes the measured pressures.<ref name="Z409" /> A standard test method was developed so that different vessels and laboratories obtain reproducible results.<ref name="Z409" /> In the United States, the American Society for Testing and Materials standard ASTM E1226 (1988 edition) is used for KSt in a 20-litre vessel.<ref name="Z415">Zalosh (2002), p. 3-415.</ref> ASTM E1515 (1998 edition) specifies a pyrotechnic igniter of 2,500 or 5,000 J in a 20-litre vessel for the minimum explosible concentration. Some materials are so sensitive to the igniter that tests in a 1 m³ vessel are needed.<ref name="Z404" />

== Secondary explosions ==

Dust explosions have a particular tendency to cause damaging secondary explosions.<ref name="Z409" /> A first explosion can burst a piece of process equipment that cannot withstand the full closed-vessel pressure, sending out a blast wave and strong air movement. This disturbance often lifts dust that has settled on walls and floors into a new cloud.<ref name="Z409" /> Even if this cloud fills only a small part of the building, the flame escaping from the broken equipment often ignites it.<ref name="Z409" /> In an occupied building, the secondary explosion can cause many casualties as well as structural damage.<ref name="Z409-410" />
[[File:fse-dust-explosion-v2.svg|thumb|upright=1.5|alt=A primary vessel explosion lifts building dust into a cloud that ignites in a secondary explosion.|Secondary explosions can involve dust accumulated outside the original equipment. Based on Zalosh (2002), pp. 3-409–3-410.]]

A thin layer of dust can be enough. In a worked example, Zalosh considers bituminous coal dust lying on the floor at 1,000 g/m², a layer about 2 mm thick, in a room with a 4 m ceiling.<ref name="Z410">Zalosh (2002), p. 3-410.</ref> Suppose a first explosion lifts this dust into a worst-case cloud of 500 g/m³ in the lower part of the room. Without venting, the secondary explosion then raises the pressure by about 4.6 bar.<ref name="Z410" /> That is at least thirty times the 7 to 15 kPa at which unrestrained brick walls typically fail.<ref name="Harris">Harris (1983), as cited in Iqbal and Salley (2004), p. 15-13.</ref> NUREG-1805 also lists secondary explosions leading to catastrophic damage among the hazards of a deflagration, together with equipment failure and injury.<ref name="IS-15-3" />

== Prevention and protection ==

Dust explosion protection interrupts the chain of events at one of three points: preventing an explosive cloud, removing ignition sources, or limiting the pressure rise.<ref name="Z402" /> Where the dust concentration in equipment cannot be kept below the minimum explosible concentration, [[inerting]] adds an inert gas to lower the oxygen concentration.<ref name="Z404" /> With carbon dioxide, the limiting oxygen concentration for organic dusts lies between 11 and 15 per cent by volume, but the values for some metals are much lower.<ref name="Z404" /> Zirconium powder has a limit of zero, a sign of pyrophoric behaviour, that is, spontaneous combustion on exposure to air.<ref name="Z404" /><ref name="IS-F47">Iqbal and Salley (2004), p. F-47.</ref> In the United States, NFPA 69 (1997 edition) states that oxygen should be kept at least 2 percentage points below the limit under continuous monitoring, and further below it otherwise.<ref name="Z403" />

Ignition sources are controlled, for example, by earthing equipment to prevent electrostatic discharges.<ref name="Z402" /> In the coal mill example, a temperature monitor could stop the mill well before friction or smouldering coal heated its wall to 600 °C.<ref name="Z405" /> In the [[hazardous area classification]] summarised in NUREG-1805, a US guide, Division 1 covers places where flammable gases or combustible dust may be present at ignitable concentrations during normal operation.<ref name="IS-B24">Iqbal and Salley (2004), p. B-24.</ref> NFPA 499 (1997 edition) is a US recommended practice for classifying combustible dusts and such locations for electrical installations in chemical process areas.<ref name="IS-E">Iqbal and Salley (2004), pp. E-3, E-8.</ref>

[[Explosion venting]] releases the combustion gases through openings, usually covered by panels or rupture discs, so that the pressure stays below the level that would damage the enclosure.<ref name="Z414" /> Perhaps the most extensive large-scale venting tests were those of Bartknecht and colleagues in Basel, Switzerland, mostly with dusts in vessels of 2.4 to 250 m³.<ref name="Z415" /> They used energetic igniters and worst-case dust concentrations, and their data were correlated in the various versions of the German dust venting guideline VDI 3673.<ref name="Z415" /><ref name="Z421">Zalosh (2002), p. 3-421.</ref> For low-strength enclosures, NFPA 68 (1998 edition) groups dusts by their deflagration index: below 200, from 200 to 300, and above 300 bar·m/s.<ref name="Z416" /> In one worked example, a 400 m³ electrostatic precipitator in a coal-fired power plant needed about 2 m² of vent area.<ref name="Z416-417">Zalosh (2002), pp. 3-416–3-417.</ref> Because KSt can vary widely even between coals, Zalosh stresses that the vent area should be based on samples from the actual site.<ref name="Z417" />

Explosion suppression detects an explosion in its first moments, usually with pressure detectors for dust, and discharges an extinguishing agent before the pressure reaches the damage threshold.<ref name="Z417" /> Unlike venting it releases no flame or fuel, so it suits indoor equipment, but it is costly.<ref name="Z417" /> The remaining pressure is usually below 5 per cent of the unsuppressed maximum for organic fuels. For aluminium dust, the most demanding material tested, recent tests suggest that it can now be kept to 10 to 20 per cent.<ref name="Z418">Zalosh (2002), p. 3-418.</ref> Work with dried milk powders at an Irish agricultural research facility has given evidence that water mist with very small drops may quell a dust explosion.<ref name="MB">Mawhinney and Back (2002), p. 4-330.</ref> Deflagration pressure containment instead designs a vessel and its fittings to withstand the full pressure of an internal deflagration.<ref name="IS-F20" />
[[File:fse-dust-explosion-v3.svg|thumb|upright=1.5|alt=Five layers address cloud formation, ignition, oxygen, pressure relief and vessel strength.|Dust-explosion protection acts at different points in the event sequence. Based on Zalosh (2002), pp. 3-402–3-403 and pp. 3-414–3-416.]]

== Test data and their limits ==

Explosibility data are measured in standard laboratory tests. Results depend on the ignition source, on the turbulence at the moment of ignition, and on the size and shape of the test vessel.<ref name="Z404" /><ref name="Z414" /> For a hazard evaluation, Barry lists dust explosion data for samples that reflect the process conditions among the material properties needed.<ref name="Barry">Barry (2002), p. 5-178.</ref> Two samples of the same material can behave very differently. In Zalosh's table, polyethylene with a median particle size below 10 micrometres has a KSt of 156 bar·m/s, against 54 bar·m/s for a sample of 150 micrometres.<ref name="Z404" />

Dust explosions are more difficult to model than gas explosions.<ref name="Z414" /> Venting guidelines are based on tests and do not account for the turbulence and equipment obstructions of a particular installation. Most of them also ignore how much of the enclosure is filled with the combustible mixture.<ref name="Z416" /> The vent area calculated in the precipitator example also does not allow for the weight of the vent panels.<ref name="Z417" />

Risk indexing methods for process plants take dust into account. The Dow Fire and Explosion Index adds a penalty for a dust explosion hazard. It counts this among its special process hazards, the items that increase the probability of a fire or explosion.<ref name="Watts">Watts (2002), pp. 5-129–5-130.</ref> NUREG-1805 also lists several NFPA standards that deal with dust explosions. They include NFPA 654 (2000 edition) on combustible particulate solids, NFPA 61 (2002 edition) on agricultural and food products facilities, and NFPA 484 (2002 edition) on combustible metals and metal dusts.<ref name="IS-E" />

== See also ==

* [[Self-heating]]
* [[Deflagration]]
* [[Detonation]]
* [[Vapour cloud explosion]]

== Notes ==

<references />

== References ==

* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-176–5-213). National Fire Protection Association; Society of Fire Protection Engineers.
* Beyler, C. L. (2002b). Flammability limits of premixed and diffusion flames. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-172–2-187). National Fire Protection Association; Society of Fire Protection Engineers.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-211–2-228). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Mawhinney, J. R., & Back, G. G., III. (2002). Water mist fire suppression systems. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-311–4-337). National Fire Protection Association; Society of Fire Protection Engineers.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 2-200–2-210). National Fire Protection Association; Society of Fire Protection Engineers.
* Watts, J. M., Jr. (2002). Fire risk indexing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-125–5-142). National Fire Protection Association; Society of Fire Protection Engineers.
* Zalosh, R. (2002). Explosion protection. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-402–3-421). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Explosions & Industrial Fires]]

Society of Fire Protection Engineers

2026-11-02T18:05:05Z

Mark: Redirect to SFPE (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[SFPE]]

SFPE

2026-11-02T18:04:56Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations and sources, structure, See also, links, style (revised by Claude Opus 5.5)

'''SFPE''', the Society of Fire Protection Engineers, is an organisation in the United States that represents fire protection engineers.<ref name="NIST-201">National Institute of Standards and Technology (2005), p. 201.</ref> It is based in Bethesda, Maryland.<ref name="DiNenno-iii">DiNenno et al. (2002), pp. iii–iv.</ref> The International Fire Engineering Guidelines (IFEG, 2005) list SFPE among the organisations that publish and provide knowledge for fire engineering.<ref name="IFEG-US-05">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.5-6–0.5-10.</ref> Its publications include the ''SFPE Handbook of Fire Protection Engineering'', engineering guides on subjects such as performance-based design, and engineering standards such as one on calculating fire exposures to structures.<ref name="DiNenno-iii" /><ref name="Notarianni-42">Notarianni (2002), p. 5-42.</ref><ref name="ABCB-B1">Australian Building Codes Board (2020a), Data Sheet B1, p. 12.</ref>

SFPE has also developed a Canon of Ethics for Fire Protection Engineers, to which the IFEG refer for professional issues outside their own scope.<ref name="IFEG-US-01">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.1-1–0.1-4.</ref> Its publications are used well beyond the United States. In New Zealand, Verification Method C/VM2 (second edition, 2025) refers to the SFPE Handbook for evacuation calculations.<ref name="MBIE-26">Ministry of Business, Innovation and Employment (2025b), pp. 26, 33.</ref> In Australia, the 2020 handbook for the Fire Safety Verification Method cites SFPE engineering standards.<ref name="ABCB-H">Australian Building Codes Board (2020b), pp. 109, 113.</ref> SFPE is a separate body from the National Fire Protection Association, which publishes the SFPE Handbook and develops codes and standards of its own.<ref name="DiNenno-iii" /><ref name="Iqbal-E1">Iqbal and Salley (2004), p. E-1.</ref>

== Fire protection engineering and the society ==

SFPE describes fire protection engineering as the application of science and engineering principles to protect people and their environment from destructive fire.<ref name="IFEG-US-03">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-1–0.3-2.</ref> In this description the field includes the analysis of fire hazards. It also covers reducing fire damage through the design, construction, arrangement and use of buildings, materials, structures, industrial processes and transport systems.<ref name="IFEG-US-03" /> A third part is the design, installation and maintenance of fire detection, suppression and communication systems, and a fourth is investigation and analysis after a fire.<ref name="IFEG-US-03" /> In the SFPE wording, a fire protection engineer knows through education, training and experience how fires start and spread, and how they can be detected, controlled or extinguished.<ref name="IFEG-US-03" /> Such an engineer can also anticipate how materials, structures and processes behave in fire.<ref name="IFEG-US-03" />

The term "fire protection engineer" is common in the United States, but the IFEG mainly use "fire engineer", which they consider a better international description of the engineer who applies their design methods.<ref name="IFEG-US-01" /> The guidelines take their definition of [[Fire safety engineering|fire engineering]] from the International Organization for Standardization (ISO).<ref name="IFEG-US-03" /> In it, fire engineering is the application of engineering principles, rules and expert judgement based on a scientific appreciation of fire, its effects and the behaviour of people.<ref name="IFEG-US-03" /> Its aims include saving life, protecting property, preserving the environment and heritage, quantifying the hazards and risk of fire, and evaluating the measures needed to limit its consequences to prescribed levels.<ref name="IFEG-US-03" />

NIST, the US National Institute of Standards and Technology, counts SFPE among the organisations that represent engineers, such as the National Society of Professional Engineers.<ref name="NIST-201" /> It distinguishes these groups from the organisations that develop codes and standards, and notes that they also provide training, especially where training affects how code provisions are applied in practice.<ref name="NIST-201" /> SFPE also carries out periodic surveys of the industry to understand what roles fire protection engineers play.<ref name="IFEG-US-01" /> The IFEG list two SFPE periodicals, the ''Journal of Fire Protection Engineering'' and the ''SFPE Journal'', among the journals useful to fire engineering professionals.<ref name="IFEG-US-05" /> In New Zealand, the IFEG note that fire engineers may be approved for full membership of bodies such as SFPE once they have shown appropriate qualifications and experience. Membership of an institution does not, however, necessarily prove the competence of an individual.<ref name="IFEG-NZ-04">National Research Council of Canada et al. (2005), Part 0 (New Zealand), p. 0.4-2.</ref>

== The SFPE Handbook ==

The third edition (2002) of the ''SFPE Handbook of Fire Protection Engineering'' is copyrighted by SFPE and published by the [[NFPA|National Fire Protection Association]] (NFPA) in Quincy, Massachusetts.<ref name="DiNenno-iii" /> Philip J. DiNenno was editor-in-chief, with six section editors from consultancies, a university, NIST, NFPA and The Fire Safety Institute.<ref name="DiNenno-iii" /> Its 72 chapters, each written by named authors, are grouped into five sections: Fundamentals, Fire Dynamics, Hazard Calculations, Design Calculations and Fire Risk Analysis.<ref name="DiNenno-v">DiNenno et al. (2002), pp. v–viii.</ref> Appendices then give data such as conversion factors, thermophysical properties of materials and fuel properties.<ref name="DiNenno-v" />
[[File:fse-sfpe-v1.svg|thumb|upright=1.5|alt=Fundamentals and hazard methods support design and risk analysis in the handbook.|The handbook combines specialist technical subjects. Based on DiNenno et al. (2002), pp. iii–vii.]]

In his preface, DiNenno describes the handbook as a contribution towards documenting and integrating the theoretical and applied bases of fire safety engineering.<ref name="DiNenno-ix">DiNenno et al. (2002), pp. ix–x.</ref> The rapid assimilation of performance-based design had, in his view, underscored its importance.<ref name="DiNenno-ix" /> The third edition added chapters on heat fluxes from fires to surfaces, water mist systems and computer field modelling, and more material on risk assessment.<ref name="DiNenno-ix" /> Part of the new material on radiation heat transfer came from an SFPE technical committee working towards consensus on engineering methods.<ref name="DiNenno-ix" /> The editors expected future editions to include the work of several engineering consensus groups aiming at a consensus-based standard of care in fire safety engineering.<ref name="DiNenno-ix" />

Other documents draw on the handbook as well. NUREG-1805, a 2004 report for the US Nuclear Regulatory Commission, derived the technical basis of its Fire Dynamics Tools primarily from the SFPE Handbook and the NFPA Fire Protection Handbook.<ref name="Iqbal-xxxvii">Iqbal and Salley (2004), p. xxxvii.</ref> The IFEG name the SFPE Handbook among the textbooks that give methods for smoke production, smoke layer height, upper layer temperature and smoke movement.<ref name="IFEG-2-5">National Research Council of Canada et al. (2005), p. 2.5-2.</ref> In New Zealand, C/VM2 (2025) refers readers to Section 3, Chapter 13 of the fourth edition (2008) for more information on calculating the required safe egress time and on egress calculation procedures.<ref name="MBIE-26" /><ref name="MBIE-61">Ministry of Business, Innovation and Employment (2025b), p. 61.</ref>

The textbook ''Introduction to Fire Safety Engineering'' also takes values from the handbook. Its walking speeds for different groups, for example, range from 0.58 m/s for people with a walking frame to 1.25 m/s for healthy, unimpeded people.<ref name="VR-7.4">Van Rossum (2027), §7.4.</ref> From the same source it takes the smoke potential, which expresses how much light the smoke from one kilogram of burnt material blocks.<ref name="VR-6.4">Van Rossum (2027), §6.4.</ref> In fires this is usually 3,300 m²/kg, a generic average for burning building and furnishing materials.<ref name="VR-6.4" />

== Engineering guides and standards ==

Besides the handbook, SFPE publishes engineering guides that evaluate calculation methods for particular problems. In the handbook chapter on large hydrocarbon fires, Beyler explains that the methods for radiation from pool fires were evaluated and included in an SFPE engineering guide.<ref name="Beyler-272">Beyler (2002a), p. 3-272.</ref> In that guide the methods are described in full, their assumptions are identified and their limits of applicability are assessed.<ref name="Beyler-272" /> The guide also lists available input data and compares the accuracy of the methods with experimental data.<ref name="Beyler-272" /> These [[Hand calculations|hand calculations]] range from very crude initial hazard assessments to detailed methods that need more engineering effort.<ref name="Beyler-272" /> Where a simple method shows that a separation distance is far larger than needed for safety, a more rigorous analysis may not be necessary.<ref name="Beyler-272" />

A related SFPE guide of 2000 treats skin burns from thermal radiation in more detail than the handbook.<ref name="Beyler-308">Beyler (2002a), pp. 3-308, 3-313.</ref> In New Zealand, C/VM2 (2025) points to that guide where occupants escape past more than one window, because the time-dependent build-up of radiation must then be calculated.<ref name="MBIE-34">Ministry of Business, Innovation and Employment (2025b), pp. 34–35.</ref> For computer fire models, SFPE published Guidelines for Substantiating a Fire Model for a Given Application (2011). A 2016 validation study for the NRC names them as a useful reference next to the ASTM standard that the study follows.<ref name="Stroup">Stroup et al. (2016), p. 1-3.</ref>

Such guidance does not make a calculation tool self-validating. NUREG-1805 asks first-time users to read the whole report before an analysis and to apply its spreadsheet tools only within the limits of their validity.<ref name="Iqbal-xxxix">Iqbal and Salley (2004), p. xxxix.</ref> The IFEG add that even an expensive and highly sophisticated computer model does not guarantee accurate results, so all model output must be reviewed and verified.<ref name="IFEG-2-8">National Research Council of Canada et al. (2005), p. 2.8-4.</ref> They also describe a hydraulic method for evacuation from the SFPE Handbook, which assumes among other things that all occupants start to leave at the same time.<ref name="IFEG-2-8" />
[[File:fse-sfpe-v2.svg|thumb|upright=1.5|alt=Scenario inputs pass through a bounded hand calculation and independent plausibility review.|Hand calculations require valid inputs and critical review. Based on Iqbal and Salley (2004), p. xxxix and National Research Council of Canada et al. (2005), p. 2.8-4.]]

SFPE also issues engineering standards. The Australian data sheets for the Fire Safety Verification Method (2020) cite SFPE S.01 (2011), a standard on calculating fire exposures to structures, as a standardised approach to predicting flashover.<ref name="ABCB-B1" /> For fire models, it gives as criteria for flashover an upper layer temperature above 600 °C or a heat flux to the floor above 20 kW/m².<ref name="ABCB-B1" /> The accompanying handbook lists S.01 among the methods for fully developed fires.<ref name="ABCB-H" /> It names SFPE S.02 (2015) as a source of examples for checking heat transfer models, a process known as validation and verification.<ref name="ABCB-H" /> In the United States, NIST recommended in 2005 that standards committees draw on the ASCE/SFPE 29 standard for fire resistance design when they address progressive collapse under fire conditions.<ref name="NIST-206">National Institute of Standards and Technology (2005), pp. 206, 212.</ref>

== Performance-based design ==

For [[Performance-based design|performance-based design]], SFPE published its Engineering Guide to Performance-Based Fire Protection Analysis and Design of Buildings in 2000.<ref name="IFEG-US-01" /> The guide is meant for both design engineers and approving authorities.<ref name="Notarianni-42" /> Its stated intent is to help them determine and document that agreed levels of fire safety are achieved for a particular project.<ref name="Notarianni-42" /> Its steps are to define the project scope, identify goals, define objectives, develop performance criteria, develop fire scenarios, develop and evaluate candidate designs, and select and document the final design.<ref name="Notarianni-42" /> The documentation has four parts: a fire protection engineering design brief, a performance design report, detailed specifications and drawings, and a building operations and maintenance manual.<ref name="Notarianni-60">Notarianni (2002), p. 5-60.</ref>

The guide also gives a method for quantifying the fire risk from several fire scenarios. The total risk is the sum, over all fire scenarios considered, of the loss in each scenario multiplied by how often that scenario occurs.<ref name="Meacham">Meacham (2002), p. 5-161.</ref> Watts and Hall (2002) note that SFPE addresses the basics of fire risk analysis in its publications on performance-based design, and that SFPE task groups were adding further detail.<ref name="WattsHall">Watts and Hall (2002), pp. 5-6–5-7.</ref>

Other guidance builds on this work. The IFEG drew on the 2000 SFPE guide and on a Code Officials Guide to Performance-Based Design Review that SFPE produced with the International Code Council in 2004.<ref name="IFEG-US-01" /> For the United States, the IFEG call both documents good resources for deriving goals and objectives where no performance code has been adopted.<ref name="IFEG-US-02">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-9.</ref> They also mention SFPE work towards a consistent method for determining design fires.<ref name="IFEG-US-02" /> In addition, the IFEG recommend both guides as a benchmark for third-party reviewers of fire engineering reports.<ref name="IFEG-US-03-9">National Research Council of Canada et al. (2005), Part 0 (United States), pp. 0.3-8–0.3-9.</ref> In New Zealand, C/VM2 (2025) lists SFPE, with the IFEG and British Standards, among the publishers of internationally recognised documents on the fire engineering brief process.<ref name="MBIE-7">Ministry of Business, Innovation and Employment (2025b), p. 7.</ref>

== Uncertainty and limits ==

SFPE guidance does not remove uncertainty from performance-based design. Notarianni (2002) describes a review of the design process in the SFPE guide and of several case studies of real designs.<ref name="Notarianni-42" /> The review found seven barriers to documenting that agreed levels of fire safety had been reached.<ref name="Notarianni-42" /> The first two are performance criteria that are not established or agreed, and an unspecified process for choosing design fires.<ref name="Notarianni-43">Notarianni (2002), pp. 5-43–5-44.</ref> Others are assumptions about human behaviour, poorly documented limits of fire models and model outputs given as single values.<ref name="Notarianni-43" /> The last two are engineers working beyond their expertise and the lack of a standard way to include the reliability of fire protection systems.<ref name="Notarianni-43" />

Each barrier can lead to switchover, in which reasonable changes in inputs, scenarios or parameters change the decision on whether a design is acceptable.<ref name="Notarianni-42" /> In one example, two engineers who had both followed the current design guidelines for real buildings chose very different performance criteria.<ref name="Notarianni-43" /> Because model predictions are compared with such criteria, the same design can pass under one set and fail under another.<ref name="Notarianni-43" />
[[File:fse-sfpe-v3.svg|thumb|upright=1.5|alt=Changed criteria, scenarios, behaviour and model assumptions lead to different acceptability outcomes.|Uncertainty can change a design from acceptable to unacceptable. Based on Notarianni (2002), pp. 5-43–5-44.]]

Human behaviour is a particular source of uncertainty. Proulx (2002) warns that research has shown some traditional assumptions about behaviour in fires to be wrong.<ref name="Proulx">Proulx (2002), pp. 3-342–3-343.</ref> He also cites the observation that the hydraulic model of evacuation assumes occupants who are alert, able-bodied and ambulatory, and deals only with movement, not with the time people take to start.<ref name="Proulx" /> Notarianni adds that one internationally used egress model assumes that all occupants are readily mobile and leave as soon as they hear an alarm.<ref name="Notarianni-43" /> Experience shows that this is often not the case.<ref name="Notarianni-43" />

The handbook also has practical limits. Some of its equations, tables and charts keep US customary units because their data were originally developed in those units.<ref name="DiNenno-ix" /> Its notice states that neither the publisher nor the authors guarantee the accuracy or completeness of the contents, and that they supply information and opinion rather than engineering services.<ref name="DiNenno-iii" /> Where such services are needed, the notice advises seeking the help of an appropriate professional.<ref name="DiNenno-iii" />

== Ethics and professional practice ==

One of SFPE's contributions to [[Ethics in fire safety engineering|ethics in fire safety engineering]] is its Canon of Ethics for Fire Protection Engineers, which the IFEG quote in part.<ref name="IFEG-US-04">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.4-2.</ref> Its preamble calls fire protection engineering an important learned profession whose work has a direct and vital impact on the quality of life of all people.<ref name="IFEG-US-04" /> The services of fire protection engineers therefore require honesty, impartiality, fairness and equity, and must be dedicated to protecting and enhancing public safety, health and welfare.<ref name="IFEG-US-04" /> Engineers are expected to maintain and constantly improve their competence and to act with balanced regard for the interests of the public, clients, employers, colleagues and the profession.<ref name="IFEG-US-04" />

Three fundamental principles follow from the preamble. Fire protection engineers use their knowledge and skill for the enhancement of human welfare.<ref name="IFEG-US-04" /> They are honest and impartial and serve the public, their employers and their clients with fidelity.<ref name="IFEG-US-04" /> They also strive to increase the competence and prestige of their profession.<ref name="IFEG-US-04" /> The IFEG state that the canon deals with professional issues outside their own scope and should be consulted as appropriate.<ref name="IFEG-US-01" />

SFPE also has a role in education. After its World Trade Center investigation, NIST named SFPE in 2005 among the organisations affected by its recommendation to develop continuing education for fire protection engineers, structural engineers and architects.<ref name="NIST-222">National Institute of Standards and Technology (2005), pp. 222–223.</ref> It also named SFPE for training material on computational fire dynamics and thermostructural analysis tools.<ref name="NIST-222" /> For NIST's report on the active fire protection systems of the World Trade Center, an SFPE engineering programmes manager supplied introductory and summary material.<ref name="Evans">Evans et al. (2005), p. xxvii.</ref> Its purpose was to give all readers a common basis for understanding the results.<ref name="Evans" />

== Relationship with NFPA and with regulation ==

SFPE and NFPA are separate organisations with different roles. NFPA develops and publishes consensus codes and standards, whereas NIST groups SFPE with the organisations that represent engineers.<ref name="Iqbal-E1" /><ref name="NIST-201" /> The IFEG list the two as distinct bodies that publish fire engineering knowledge.<ref name="IFEG-US-05" /> They work together on publications: SFPE holds the copyright of the SFPE Handbook and NFPA publishes it.<ref name="DiNenno-iii" /> NIST also named both in 2005 for work on standard methods for multi-floor design fire scenarios.<ref name="NIST-206" />

SFPE guides and standards are not regulations in themselves. A NIST report on the World Trade Center explains that trade associations and professional societies develop practices that may guide how buildings are designed and built.<ref name="Lew">Lew et al. (2005), p. 142.</ref> Such practices are not strictly enforceable unless a code refers to them, but they represent a consensus of what is reasonable or prudent.<ref name="Lew" /> Where a regulatory document does refer to SFPE material, it does so selectively. C/VM2 (2025), for example, cites the SFPE Handbook and an SFPE guide only in particular comments and clauses.<ref name="MBIE-61" /> Compliance with the New Zealand Building Code still requires each of its own ten design scenarios to be satisfied.<ref name="MBIE-7" />

C/VM2 is meant for professional fire engineers who are proficient in fire engineering modelling methods.<ref name="MBIE-7" /> They are expected to apply appropriate judgement to model inputs and results.<ref name="MBIE-7" /> The IFEG likewise allow engineering judgement where valid methods or verified data are not available, but require all quantification based on it to be justified in detail.<ref name="IFEG-1-8">National Research Council of Canada et al. (2005), p. 1.8-10.</ref> For the United States, they give the fire engineer the task of evaluating a performance design and the authority having jurisdiction the task of assessing and approving it.<ref name="IFEG-US-0211">National Research Council of Canada et al. (2005), Part 0 (United States), p. 0.2-11.</ref>

== See also ==

* [[Acceptance criteria]]
* [[Fire scenario]]
* [[Fire safety objectives]]
* [[Qualitative design review]]
* [[Building regulations]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Beyler, C. L. (2002a). Fire hazard calculations for large, open hydrocarbon fires. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-268–3-314). National Fire Protection Association; Society of Fire Protection Engineers.
* DiNenno, P. J., Drysdale, D., Beyler, C. L., Walton, W. D., Custer, R. L. P., Hall, J. R., Jr., & Watts, J. M., Jr. (Eds.). (2002). ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Institute of Standards and Technology. (2005). ''Final report on the collapse of the World Trade Center towers'' (NIST NCSTAR 1).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Proulx, G. (2002). Movement of people: The evacuation timing. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-342–3-366). National Fire Protection Association; Society of Fire Protection Engineers.
* Stroup, D., Lindeman, A., McGrattan, K., Peacock, R., Overholt, K., Joglar, F., LeStrange, S., & Montanez, S. (2016). ''Verification and validation of selected fire models for nuclear power plant applications: Supplement 1'' (NUREG-1824, Supplement 1; EPRI 3002002182). U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research; Electric Power Research Institute.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Safety Design & Regulation]]

Risk of fire

2026-11-02T18:03:49Z

Mark: Redirect to Fire risk (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire risk]]

Fire risks

2026-11-02T18:03:43Z

Mark: Redirect to Fire risk (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire risk]]

Fire risk

2026-11-02T18:03:27Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, See also, links, style (revised by Claude Opus 5.5)

'''Fire risk''' is the potential for a fire to cause unwanted, adverse consequences to human life, health, property or the environment.<ref name="WH-5-3">Watts and Hall (2002), p. 5-3.</ref> It brings together three questions: what could happen, how bad it would be, and how likely it is.<ref name="WH-5-1">Watts and Hall (2002), pp. 5-1–5-2.</ref> A fire risk therefore depends both on the consequences of possible fires and on the likelihood that they occur. It describes the uncertainty of a loss, not a loss that is certain to happen.<ref name="WH-5-1" /> Every decision related to fire safety is in effect a fire risk decision, whether or not it is treated as one.<ref name="WH-5-1" />
[[File:fse-fire-risk-v1.svg|thumb|upright=1.5|alt=What could happen, how likely and how severe lead to a risk evaluation.|Fire risk combines event scenarios, likelihood and consequences. Based on Watts and Hall (2002), pp. 5-1–5-3 and Meacham (2002), pp. 5-154–5-156.]]

Zero risk is not an achievable goal, because no technology is completely reliable and natural events such as lightning and earthquakes can also cause fires.<ref name="WH-5-4">Watts and Hall (2002), p. 5-4.</ref> The practical questions are how large the remaining risk is and whether it is acceptable. Accepting a level of risk requires a value judgement, and people make such judgements in different ways.<ref name="WH-5-1" /> Fire risk is estimated from [[Fire statistics|fire statistics]], usage data and laboratory tests, and the result is then judged for its acceptability.<ref name="HallAhrens-5-65">Hall and Ahrens (2002), p. 5-65.</ref><ref name="WH-5-3" />

== Hazard, consequence and probability ==

A hazard is a chemical or physical condition that has the potential to cause damage to people, property or the environment.<ref name="WH-5-3" /> An analysis of what could happen and how bad it would be, without considering how likely it is, is called a fire hazard analysis. A fire risk analysis adds the likelihood. A sequence of events that ends in a fire loss is called a scenario.<ref name="WH-5-1" /> For a whole building, the fire risk is the full spread of possible events and their consequences, not the outcome of one scenario.<ref name="WH-5-3" />

Consequences describe how bad a fire would be if it happened. They range from deaths and damage to property to intangible losses such as business interruption, environmental damage and the destruction of cultural objects. A consequence can be direct, such as damaged property, or indirect, such as a company that is out of business for several days. It can also be objective, such as a replacement cost, or subjective, such as the pain and suffering of an injury.<ref name="WH-5-1" /> In building fire risk analysis, the main things of value are life safety, property, business continuity, the environment and heritage.<ref name="Meacham-5-153">Meacham (2002), pp. 5-153–5-154.</ref>

Risk is usually estimated by combining the probability that an event occurs with the consequence of the event if it does occur.<ref name="WH-5-3" /> The terminology is not consistent: a committee of the Society for Risk Analysis found 17 different definitions of risk.<ref name="WH-5-3" /> The SFPE Handbook also describes fire risk as the possibility of an unwanted outcome in an uncertain situation, where fire may cause loss or harm to something that is valued.<ref name="Meacham-5-153" /> A related term is the fire safety level, which the Australian Fire Safety Verification Method handbook (2020) calls the reciprocal of fire risk: when the risk to occupants falls, the safety level rises.<ref name="ABCB-140">Australian Building Codes Board (2020b), p. 140.</ref>

== Frequency and probability ==

A frequency states how often an event occurs in a period, such as the number of fires per year. On its own it is not a probability, because the number of possible occurrences is also needed.<ref name="Meacham-5-159">Meacham (2002), p. 5-159.</ref> In a hypothetical example, 20 fires a year in toasters that are switched on 20 million times a year give a probability of one in a million per start.<ref name="Meacham-5-159" /> Fire incident data therefore have to be combined with usage or exposure data, such as the number of appliances in use or the floor area of a type of building.<ref name="HallAhrens-5-65" />

There are two views of probability. In the frequency view, probability is the proportion of the time that an event occurs in the long run. In the subjective view, it measures how strongly a person believes that an event will occur.<ref name="WH-5-3" /> Fires are relatively rare, and buildings and their contents change over time, so past losses are a limited guide to future ones. This is a strong argument for using subjective probabilities, based on current knowledge and judgement, in building fire risk analysis.<ref name="Meacham-5-159" />

The amount of available data differs widely. For US homes there are very many recorded fires with limited detail, while for US nuclear power plants there are far fewer fires but much more detail on each. For a single existing building there are very few fires at all. In fire safety engineering, risk analysis is therefore mostly used for an application or a class of facility with a considerable fire loss history.<ref name="WH-5-3" />

== Typical values ==

The frequency of fire depends strongly on the use of a building. In British Standards Institution data from 2001, quoted in the International Fire Engineering Guidelines (2005), a dwelling had about 0.003 fire starts per year and an office about 0.006. Schools and industrial buildings had about 0.04, entertainment venues about 0.12 and hospitals about 0.3 fire starts per building per year. The guidelines warn that such values may have changed with new technologies and materials.<ref name="IFEG-3-2-2">National Research Council of Canada et al. (2005), p. 3.2-2.</ref> Finnish data show that the number of fires per square metre falls as buildings get larger, while the number per building generally rises with floor area.<ref name="IFEG-3-2-3">National Research Council of Canada et al. (2005), p. 3.2-3.</ref>

Risk studies often sort frequencies into broad classes. One example in the SFPE Handbook calls events anticipated if they occur more often than once in 100 years. Events are unlikely between once in 100 and once in 10,000 years, and extremely unlikely between once in 10,000 and once in a million years. Rarer events are beyond extremely unlikely. Frequencies should be counted for a given loss rather than for a single scenario: 30 scenarios that each occur once in 10 million years together occur three times in a million years.<ref name="Meacham-5-166">Meacham (2002), pp. 5-166–5-167.</ref>

Reliability values are typical inputs as well. In reported US home fires, roughly one-third of smoke alarms were not working, but a general study of home installations found only one-fifth not working. Data from unreported fires suggest that the main reason is that working alarms keep many fires so small that the fire service is never called. Reported US fires suggest that sprinklers do not operate in one-sixth to one-fifth of the fires large enough to activate them, yet their real reliability could be well over 90 %.<ref name="HallAhrens-5-72">Hall and Ahrens (2002), p. 5-72.</ref>

== Individual and societal risk ==

Risk to people is often expressed in two complementary ways. [[Individual risk]] is the probability of injury or death to a person at a specified location relative to a fire or explosion source. It can be drawn as contour lines that connect points of equal risk, regardless of whether anyone is actually present there.<ref name="Barry-5-210">Barry (2002), p. 5-210.</ref> In the Australian Fire Safety Verification Method handbook (2020), individual risk is the frequency at which a person may be expected to suffer a given level of harm from a fire in the building.<ref name="ABCB-22">Australian Building Codes Board (2020b), p. 22.</ref>

[[Societal risk]] takes into account the likelihood of fires or explosions that cause multiple casualties. It is often shown as an F-N curve, which plots the frequency of events that exceed a given number of fatalities, N, against that number.<ref name="Barry-5-210" /> Such a curve requires the population at risk, the likelihood that people are present and the reliability of measures such as evacuation to be defined.<ref name="Barry-5-211">Barry (2002), p. 5-211.</ref> Barry (2002) describes these measures for the chemical process industries, where most calculations of risk to people are based on fatalities.<ref name="Barry-5-211" />
[[File:fse-fire-risk-v2.svg|thumb|upright=1.5|alt=Location-based individual contours contrast with cumulative frequency for multiple casualties.|Individual and societal risk answer different questions. Based on Barry (2002), pp. 5-210–5-211.]]

The two measures answer different questions. Individual risk shows how the risk to one person varies from place to place, while societal risk shows how often losses of many lives can occur.<ref name="Barry-5-210" /> Single-value risk indices, such as an annual predicted fatality rate, are easy to understand and useful for comparing design options. A ranking of the events that contribute most to the total helps to focus risk reduction.<ref name="Barry-5-211" /> In Australia, the Fire Safety Verification Method Standard 2022 accepts the deemed-to-satisfy provisions of the National Construction Code as reflecting societal expectations, including on individual and societal risk.<ref name="ABCB2022-7">Australian Building Codes Board (2022), p. 7.</ref>

== Acceptable risk ==

Acceptable risk is a value judgement applied to a chosen scale for measuring risk. It needs two prior decisions: how risk is measured, and whose views on acceptability count. For a practising engineer, acceptable risk is usually the risk acceptable to the client, while for an authority it is meant to be acceptable to society or to a particular community. A universally acceptable level of fire risk does not exist, because it depends on the problem and on the person judging it.<ref name="WH-5-4" />

People judge the same risk in different ways. Experts mainly weigh the calculated reduction in fire risk, while ordinary people also weigh costs and other needs. Enforcers act on behalf of society, and managers such as builders are most directly affected by the costs.<ref name="WH-5-1" /> The reduced fire risk of a home sprinkler system, for example, appears to be valued less by the average citizen than the benefit of a new car.<ref name="WH-5-1" /> Risks that are objectively equal are also perceived differently: people prefer certain over uncertain, familiar over unfamiliar, voluntary over involuntary and ordinary over dramatic risks.<ref name="WH-5-3" /> Dying in a fire is perceived as worse than dying in a car accident, and most people who die in fires die at home.<ref name="VR-7">Van Rossum (2027), §7.</ref>

Reducing fire risk may even increase other risks, as with the potential damage to the ozone layer from halon extinguishing agents. The goal that comes closest to zero risk is risk as low as is technically possible. In fire protection engineering, this may mean accepting the residual risk after all identified risk reduction measures have been adopted. A complication is that this residual risk may then be perceived as zero, although a non-zero risk remains.<ref name="WH-5-4" /> In Australia, workplace health and safety legislation also requires safe design, which a code of practice defines as eliminating risks to health and safety or, if this is not [[ALARP|reasonably practicable]], minimising them.<ref name="ABCB-25">Australian Building Codes Board (2020b), p. 25.</ref>

Building regulations rarely state an acceptable risk in numbers. The Australian Fire Safety Verification Method Standard 2022 notes that the National Construction Code contains no specific safety targets. A design assessed with this method must therefore be at least equivalent to the deemed-to-satisfy provisions.<ref name="ABCB2022-7" /> It adds that a full quantitative probabilistic risk assessment would ideally be used, but the tools and data for it are not included. The method instead permits a simple deterministic comparison of available and required escape times, with additional checks.<ref name="ABCB2022-18">Australian Building Codes Board (2022), p. 18.</ref>

In the Netherlands, where no risk-based limit values exist, the residual risk can be expressed as an acceptable probability of failure. One way to set it is by comparison with a reference situation that follows the rules.<ref name="VR-1-2">Van Rossum (2027), §1.2.</ref><ref name="VR-1-4">Van Rossum (2027), §1.4.</ref> In performance-based design, deciding which consequences matter is often described as setting fire safety goals, [[Fire safety objectives|fire safety objectives]] and criteria.<ref name="Meacham-5-155">Meacham (2002), p. 5-155.</ref>

== Fire statistics as evidence ==

Fire incident data show how often fires start and how severe they are. In the United States, the national fire incident reporting system collects roughly a million fires a year, but only about half of the fires reported to fire departments. A separate survey of fire departments is therefore used to scale the data up to national estimates. Fires with an unknown cause must be allocated over the known causes. If they are ignored while the share of unknowns falls, every known cause can appear to grow although the total number of fires stays the same.<ref name="HallAhrens-5-67">Hall and Ahrens (2002), pp. 5-67–5-68.</ref>

Not every fire appears in these statistics. Fires handled by the occupants or by private fire brigades are not reported, and fires in buildings with sprinklers or good detection are more likely to be controlled on site. Anecdotes, such as reports of large fires, show the range of fires that can happen but cannot be used to estimate rates or probabilities. Detailed databases that are not statistically representative can also mislead, so analysts should not give up statistical validity for detail.<ref name="HallAhrens-5-69">Hall and Ahrens (2002), pp. 5-69–5-70.</ref>

Data on the reliability of fire protection systems are scarce.<ref name="HallAhrens-5-69" /> Expert estimates tend to rate reliable systems even higher and unreliable systems even lower than they really are. Inspection and testing records usually come from well-maintained properties, so they show better reliability than typical buildings achieve. They can also miss short-lived failures, such as a door blocked open.<ref name="HallAhrens-5-71">Hall and Ahrens (2002), p. 5-71.</ref>

== Assessing and reducing fire risk ==

Fire risk analysis is a structured approach to decision making under uncertainty. A general procedure identifies the fire hazards, estimates their consequences and probabilities, identifies options to control them, estimates how each option changes the risk, and selects the protection.<ref name="WH-5-4" /> Methods of [[Fire risk assessment|fire risk assessment]] range from checklists and written recommendations through risk indexing to probabilistic methods.<ref name="WH-5-4" /> Checklists and written recommendations do not quantify risk: a design passes if it follows them, and the residual risk is never evaluated.<ref name="WH-5-5">Watts and Hall (2002), p. 5-5.</ref>

A risk matrix sorts hazards by classes of consequence and likelihood, and each cell can record whether such risks are acceptable or how they should be reduced. Probabilistic methods are the most informative, because their results can be traced back through explicit assumptions, data and relationships. Common tools are event trees, which follow the possible outcomes after an initiating event in time order, and fault trees, which show the combinations of system states that lead to an outcome.<ref name="WH-5-5" />

Risk can be reduced at several points in the chain from cause to consequence. The SFPE Handbook describes a causal sequence from an initiating event through its outcome and the exposure of people or property to the final consequences. The sequence can be interrupted at each of these points, by blocking the event, the outcome, the exposure or the consequence.<ref name="Meacham-5-157">Meacham (2002), p. 5-157.</ref> In the chemical process industries, some measures reduce how often incidents occur, such as preventive maintenance, control of ignition sources and operator training. Others reduce how severe they are, such as gas and fire detection, fireproofing of steel and water sprays.<ref name="Barry-5-211" />
[[File:fse-fire-risk-v3.svg|thumb|upright=1.5|alt=Ignition, fire development, exposure and consequences offer different intervention points.|Risk reduction can act at several points in the fire scenario. Based on Meacham (2002), pp. 5-157–5-159 and Barry (2002), p. 5-211.]]

Measures only reduce risk if they work when they are needed. Typical reliability questions are whether the battery in a smoke alarm works, whether a sprinkler valve is open and whether a fire door is blocked open.<ref name="WH-5-6">Watts and Hall (2002), p. 5-6.</ref> A US Nuclear Regulatory Commission guide lists causes of sprinkler failure. Examples are a closed water supply valve, an empty tank and a fire pump that fails to start, for instance after a power failure.<ref name="NUREG-10-2">Iqbal and Salley (2004), p. 10-2.</ref> Failures can also share a common cause, as when a failure of the fire detection system stops a smoke control system from working as intended.<ref name="ABCBDS-C4">Australian Building Codes Board (2020a), Data Sheet C4, p. 131.</ref>

== Uncertainty and variability ==

Fire risk estimates are always uncertain. Unwanted combustion is perhaps the least predictable common physical phenomenon, and uncertainty analysis should underpin the choice of safety factors and safety margins. This concerns the uncertainty of the engineer about how large a risk is, not the uncertainty of a potential victim about whether a fire loss will occur.<ref name="WH-5-6" /> A totally objective way to measure fire risk does not exist, because defining the problem, collecting data and combining information all involve subjective judgements.<ref name="WH-5-3" />

Uncertainty and variability are different things. It may not be known how many people will be exposed, which is uncertainty, while the people who are exposed differ from each other, which is variability.<ref name="Meacham-5-159" /> Scientific uncertainties come from theories and models, from data and inputs, from limits of the calculation, from the level of detail and from how well a model represents reality. Further uncertainty lies in human behaviour, in perceptions of risk and values, and in decision making itself.<ref name="Meacham-5-160">Meacham (2002), p. 5-160.</ref>

Calculations can hide much of this uncertainty. Fire models give single values, such as a detector activation time of 121 s, although the real time may be longer or shorter. One widely used egress model assumes that all occupants are readily mobile and start leaving as soon as they hear an alarm, which experience shows is often not the case. In a full uncertainty analysis, only the inputs that could change the decision on whether a design is acceptable, a change called switchover, need detailed quantitative treatment.<ref name="Notarianni-5-43">Notarianni (2002), pp. 5-43–5-44.</ref>

Design practice also handles variability and uncertainty in simpler ways. The Dutch national annex to Eurocode 1 (NEN-EN 1991-1-2/NB), for example, gives both average fire loads and 80 % fractiles for a more conservative approach. An 80 % fractile is a value that the actual fire load does not exceed in 80 % of cases.<ref name="VR-8-5">Van Rossum (2027), §8.5.</ref> An escape time analysis keeps a safety margin between the available and the required escape time, because many of the inputs are uncertain. The more reliable the inputs are, the smaller the margin needs to be.<ref name="VR-7-1">Van Rossum (2027), §7.1.</ref>

== See also ==

* [[Event tree analysis]]
* [[Fault tree analysis]]
* [[Quantitative risk assessment]]
* [[Reliability of fire protection systems]]
* [[Uncertainty analysis]]
* [[Fire safety concepts tree]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020a). ''Data sheets: Fire Safety Verification Method'' (Handbook annex, Print version 1.1).
* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Barry, T. F. (2002). Quantitative risk assessment in chemical process industries. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-176–5-213). National Fire Protection Association; Society of Fire Protection Engineers.
* Hall, J. R., Jr., & Ahrens, M. J. (2002). Data for engineering analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-65–5-78). National Fire Protection Association; Society of Fire Protection Engineers.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Meacham, B. J. (2002). Building fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-153–5-175). National Fire Protection Association; Society of Fire Protection Engineers.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Notarianni, K. A. (2002). Uncertainty. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-40–5-64). National Fire Protection Association; Society of Fire Protection Engineers.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.
* Watts, J. M., Jr., & Hall, J. R., Jr. (2002). Introduction to fire risk analysis. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-1–5-7). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Fire Risk Analysis]]

Manual firefighting

2026-11-02T18:02:42Z

Mark: Redirect to Firefighting (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Firefighting]]

Manual fire suppression

2026-11-02T18:02:36Z

Mark: Redirect to Firefighting (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Firefighting]]

Fire-fighting

2026-11-02T18:02:30Z

Mark: Redirect to Firefighting (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Firefighting]]

Fire fighting

2026-11-02T18:02:23Z

Mark: Redirect to Firefighting (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Firefighting]]

Firefighting

2026-11-02T18:02:00Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, country labels, See also, links, style (revised by Claude Opus 5.5)

'''Firefighting''' is the work of controlling and extinguishing fires, together with the rescue and protection tasks that go with it. A glossary published by the US Nuclear Regulatory Commission treats it as fire suppression, either manual, with hoses, portable extinguishers or manually operated fixed systems, or automatic, by systems using water, Halon or carbon dioxide.<ref name="NUREG-F29">Iqbal and Salley (2004), p. F-29.</ref> Besides attacking the fire, fire services search for and rescue occupants, protect property and limit harm to the environment.<ref name="IFEG-2.9-3">National Research Council of Canada et al. (2005), p. 2.9-3.</ref> Early action matters: an automatic extinguishing system generally intervenes while the fire is still in its growth stage, so the fire cannot become fully developed.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref> A fire service that arrives after flashover, by contrast, may have no effect on the fire itself.<ref name="IFEG-1.9-7">National Research Council of Canada et al. (2005), p. 1.9-7.</ref> Tactics differ between countries and situations; the Dutch fire service, for example, prefers to fight building fires from outside and attacks from inside only when an exterior attack fails and this can be done safely.<ref name="NIPV-43">Van der Graaf et al. (2021/2023), p. 43.</ref>

== Who fights fires and what they aim for ==

Many fires are fought first by the people who discover them. In the decision process that Bryan describes, an occupant who has recognised a fire chooses between flight, leaving the building, and fight, fetching an extinguisher or raising the alarm.<ref name="Bryan-3-318">Bryan (2002), p. 3-318.</ref> In a British study of 2,193 people at 952 fires, 14.9 % made fighting the fire their first action. In a US study of residential fires the share was 10.4 %, and in both studies men were more often active in fighting the fire.<ref name="Bryan-3-322">Bryan (2002), pp. 3-322–3-323.</ref> The Australian handbook to the Fire Safety Verification Method (print version 1.1, 2020) notes that many smouldering and small flaming fires are dealt with by occupants and never reported. Estimates of how often design fires occur are therefore commonly based on reported fires, ignoring suppression by occupants.<ref name="ABCBH-61">Australian Building Codes Board (2020b), pp. 61–62.</ref>

At industrial sites, trained staff and private fire brigades take part as well. The US glossary describes a fire watch: people trained to recognise fire hazards, to use fire extinguishers and to follow the proper notification procedures.<ref name="NUREG-F29" /> At US nuclear power plants, the fire brigade operates fixed systems by hand, removes fuel sources, switches off electrical systems and uses portable extinguishers and hose streams.<ref name="Nowlen-P5">Nowlen et al. (2005b), p. P-5.</ref> The International Fire Engineering Guidelines (2005 edition) include such private brigades, for example the brigade of an industrial complex, in their analysis of fire service intervention.<ref name="IFEG-1.9-1">National Research Council of Canada et al. (2005), p. 1.9-1.</ref>

The aims of firefighting go beyond putting out flames. According to the guidelines, fire services are commonly responsible for search and rescue, containing and extinguishing the fire and protecting property. They also protect the environment and the community, for example from contaminated firefighting water running off a chemical warehouse.<ref name="IFEG-2.9-3" /> Control means that the fire is kept from growing, for instance by wetting nearby combustibles and cooling the hot gases under the ceiling, while extinguishment is the complete suppression of all burning material.<ref name="NUREG-F25">Iqbal and Salley (2004), p. F-25.</ref> An attack can be offensive, applying water to the fire, or defensive, using hose streams to protect adjoining property, or both.<ref name="IFEG-1.9-4">National Research Council of Canada et al. (2005), p. 1.9-4.</ref>

== How fires are put out ==

[[Extinguishing mechanisms]] work by separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or the flame, or interfering with the chemistry of combustion. Several of them often act at once. Water on a burning solid cools the solid, so that it releases less flammable gas, and cools the flame, so that less heat reaches the fuel. Steam can keep oxygen away in some confined conditions, and a fog of fine droplets can block heat radiation.<ref name="NUREG-B15">Iqbal and Salley (2004), p. B-15.</ref> Water is the most common extinguishing agent because it is widely available, cheap and able to absorb a great deal of heat. Fleming gives about 2,590 kJ per US gallon heated from 21 °C and turned into steam, or roughly 680 kJ per litre.<ref name="Fleming-4-72">Fleming (2002), p. 4-72.</ref>
[[File:fse-firefighting-v1.svg|thumb|upright=1.5|alt=Control, extinction and exposure protection are supported by cooling, blanketing and chemical action.|Firefighting objectives and mechanisms must match the incident. Based on Iqbal and Salley (2004), p. B-15 and Fleming (2002), p. 4-72.]]

Water does not suit every fire. It is inappropriate for certain water-reactive materials, with which it can produce heat, flammable or toxic gases or explosions. Most hydrocarbon fuels are lighter than water and do not mix with it, so they float on the water and keep burning.<ref name="Fleming-4-72" /> On hot oil or fat, water can sink below the surface, turn to steam and throw out burning oil in a boilover.<ref name="NUREG-B58">Iqbal and Salley (2004), p. B-58.</ref> In the US classification of fires, water must never be used on Class D fires, which involve combustible metals such as magnesium, sodium and lithium.<ref name="NUREG-B16">Iqbal and Salley (2004), p. B-16.</ref>

Foam is the main alternative to water, used mostly on burning liquids.<ref name="NUREG-B58" /> Firefighting foam consists of air-filled bubbles made from water mixed with a foam concentrate, typically at 1, 3 or 6 percent. It floats on the fuel and forms a layer that keeps air out and stops the fuel from evaporating, so the fire goes out once the whole surface is covered. Low-expansion foam works well on a pool of liquid but much less well on running fuel or a pressurised spray, where an extra agent such as dry chemical is used.<ref name="Scheffey-4-88">Scheffey (2002), p. 4-88.</ref> Heat breaks foam down, so it must be applied fast enough and in large enough amounts to keep a layer over the fuel.<ref name="NUREG-B59">Iqbal and Salley (2004), p. B-59.</ref> A ruptured foam blanket can let the fire burn back and put firefighters at risk.<ref name="NUREG-B60">Iqbal and Salley (2004), p. B-60.</ref>

Dry chemical powders probably act mainly on the chemistry of the flame, and they also absorb heat, block radiation and, in one type, coat the burning surface. They leave residue that needs thorough cleaning and can corrode equipment.<ref name="NUREG-B55">Iqbal and Salley (2004), pp. B-55–B-56.</ref> In a 2001 fire at the Point Beach nuclear plant in the United States, the fire brigade discharged about 32 kg of dry chemical from three extinguishers without success. The fire was finally put out with 57 to 76 L of water, and white dust covered large parts of the containment building.<ref name="NUREG-H29">Iqbal and Salley (2004), p. H-29.</ref> Gaseous agents such as Halon 1301 put out visible flames almost at once, but glowing combustion inside a solid fuel can continue and re-ignite when air is let back in.<ref name="NUREG-B43">Iqbal and Salley (2004), pp. B-43–B-44.</ref>

== Manual firefighting: extinguishers, hoses and water ==

A [[Fire extinguisher]] is one of the means of manual suppression named in the US glossary, alongside hoses and manually operated fixed systems.<ref name="NUREG-F29" /> In the United States, its rating combines a number for relative effectiveness with a letter for each class of fire on which it has proved effective.<ref name="NUREG-F25" /> Class A covers ordinary combustibles such as wood and paper, B flammable liquids and gases, and C fires involving energised electrical equipment. Class D covers combustible metals and K cooking oils and fats.<ref name="NUREG-B16" /> Dry chemical agents are safe on electrical fires as far as electric shock is concerned, but they can damage delicate equipment.<ref name="NUREG-B55" />

Hose lines need a water supply that the fire service can reach. A [[Fire hydrant]] provides water to the pumpers of the fire department.<ref name="NUREG-F26">Iqbal and Salley (2004), p. F-26.</ref> In tall buildings, [[Dry and wet risers]] carry water to outlets on the floors, so firefighters can connect their hoses near the fire instead of laying them from the street.<ref name="NUREG-F61">Iqbal and Salley (2004), pp. F-61–F-62.</ref><ref name="Hopkins-21">Hopkins et al. (2005), p. 21.</ref> In New York City, supplying extra water to a building's fire protection systems is a routine fire department operation.<ref name="Hopkins-xlii">Hopkins et al. (2005), p. xlii.</ref> Reaching the hydrants, inlets and fire floor is a matter of [[fire service access]], which New Zealand's Verification Method C/VM2 (second edition, 2025) covers in its scenario for firefighting operations.<ref name="CVM2-53">Ministry of Business, Innovation and Employment (2025b), p. 53.</ref>

The water flow must match the size of the fire. The Netherlands Institute for Public Safety (NIPV) gives rules of thumb for cooling capacity. A high-pressure jet of 125 L/min is generally sufficient for a fire of up to about 2.5 MW, and a low-pressure jet of 450 L/min for up to about 10 MW.<ref name="NIPV-45">Van der Graaf et al. (2021/2023), p. 45.</ref> For comparison, Van Rossum gives about 2.5 MW for an average living-room sofa and a peak of 8.5 MW for a car.<ref name="VR-4.5">Van Rossum (2027), §4.5.</ref> He notes that such heat release data help the fire service judge whether a fire can still be fought with the flow its vehicle delivers at low, medium or high pressure.<ref name="VR-8.6">Van Rossum (2027), §8.6.</ref>

Time is often decisive. In an aircraft fuel spill fire, the aluminium skin of the aircraft can burn through in about 1 minute. The cabin becomes unsurvivable once the windows melt out after about 3 minutes.<ref name="Scheffey-4-103">Scheffey (2002), p. 4-103.</ref> Airport rescue and firefighting vehicles are designed to reach an incident on the airport within 2 to 3 minutes. Once there, they must apply agent to control the fire within 1 minute, a critical time recognised by US and international aviation and fire protection bodies.<ref name="Scheffey-4-103" />

== Automatic systems and the fire service ==

Automatic sprinklers often act long before firefighters can. Human response, from discovery of the fire to the travel of the fire brigade, usually takes much longer than the time sprinklers need to control a fire in its early stages. Sprinklers are designed to control a fire, but they often put it out, because the wetted materials around it can no longer heat up to their ignition temperature.<ref name="NUREG-10-1">Iqbal and Salley (2004), pp. 10-1–10-2.</ref> Even where sprinklers do not suppress a fire, their cooling can protect the structure until the fire is extinguished by other means.<ref name="Fleming-4-72" />

Manual and automatic firefighting both depend on the water supply. Sprinkler systems fail when a supply valve is closed, a water tank is empty, a fire pump does not start or loses its power, or the pipes and heads are blocked or corroded.<ref name="NUREG-10-2">Iqbal and Salley (2004), p. 10-2.</ref> At World Trade Center 7, the sprinklers on the lower 20 floors depended on one automatic fire pump and on the city main.<ref name="Hopkins-xli">Hopkins et al. (2005), p. xli.</ref> After the collapse of WTC 1, the fire department could not provide firefighting or supplementary water to the building.<ref name="Hopkins-xliv">Hopkins et al. (2005), p. xliv.</ref> In the SFPE Handbook, Siu warns that many fire risk studies for nuclear power plants ignore the reliance of automatic and manual suppression on a common water supply, which can make their results non-conservative.<ref name="Siu-5-221">Siu (2002), p. 5-221.</ref>
[[File:fse-firefighting-v2.svg|thumb|upright=1.5|alt=Extinguisher, hydrant and hose line, and automatic sprinkler have different operating chains.|Manual and automatic suppression have different dependencies. Based on Iqbal and Salley (2004), pp. F-25–F-26 and 10-1–10-2.]]

Risk studies of US nuclear power plants estimate from past events how long manual firefighting takes. For all fire types together, NUREG/CR-6850 (2005) gives a probability of 0.46 that a fire is still burning after 10 minutes of manual suppression, and 0.10 after 30 minutes.<ref name="Nowlen-P9">Nowlen et al. (2005b), pp. P-9–P-10.</ref> These curves leave out the time to detect the fire and the response time of the fire brigade. Both must be subtracted from the time before damage occurs to find the time that is actually available for suppression.<ref name="Nowlen-P9" />

== Tactics: inside or outside, offensive or defensive ==

Firefighting tactics weigh the chance of success against the risk to firefighters. The International Fire Engineering Guidelines note that a shortage of water or of firefighters for an interior attack can change the strategy from offensive, fighting the fire, to defensive. The defensive aim is to stop the fire spreading to adjoining buildings.<ref name="IFEG-2.9-4">National Research Council of Canada et al. (2005), p. 2.9-4.</ref>

The Dutch fire service arranges its tactics in a quadrant model. The goal is either to prevent fire growth or to extinguish the seat of the fire, and the attack is made either from inside or from outside the building. Firefighters prefer to fight a fire from outside, and they carry out an interior attack only in a small room or building when an exterior attack fails and it can be done safely. A smoke-filled space is entered only if the benefits outweigh the risks, and reducing material damage is not a reason to take risks.<ref name="NIPV-43" />

The Dutch basic principles start with taking time to stop and think, followed by a reconnaissance from outside, for example with a thermal imaging camera. Three questions then decide the type of attack: is it known where the fire is, can it be reached from outside, and is there enough cooling capacity.<ref name="NIPV-44">Van der Graaf et al. (2021/2023), p. 44.</ref> If the fire cannot be found, reached and cooled from outside, large buildings are fought defensively and considered beyond saving.<ref name="NIPV-44" /> In a small building an offensive interior attack may still be possible, with control of the doors, the building kept closed where possible and water on the fire as quickly as possible.<ref name="NIPV-63">Van der Graaf et al. (2021/2023), p. 63.</ref>

An interior attack also needs a short route through smoke and enough cooling capacity, and the commanding officer on site makes the final decision.<ref name="NIPV-45" /> Van Rossum stresses the same point for engineering studies: a positive result does not mean that the fire service will attack from inside, because that decision always rests with the fire service on site.<ref name="VR-9.3">Van Rossum (2027), §9.3 (Results from zone models).</ref> The Australian handbook, summarising limits from the Fire Brigade Intervention Model, adds that search and rescue cannot be carried out in a room that has reached flashover.<ref name="ABCBH-113">Australian Building Codes Board (2020b), p. 113.</ref>

== Ventilation, backdraft and smoke explosions ==

Firefighters also change the ventilation of a burning building. [[Positive pressure ventilation]] uses fans to blow fresh air into an enclosure, creating a pressure difference that drives the existing air and combustion products out through an exit opening. It is used to influence the degree of ventilation, to assist firefighting and to influence the burning itself.<ref name="NUREG-F46">Iqbal and Salley (2004), p. F-46.</ref>
[[File:fse-firefighting-v3.svg|thumb|upright=1.5|alt=Fan airflow changes smoke flow and can supply oxygen to hot unburned gases.|Ventilation can alter both visibility and combustion conditions. Based on Iqbal and Salley (2004), p. F-46 and Van Rossum (2027), §4.9.]]

Adding air is risky when a fire is short of oxygen. In a ventilation-controlled fire the oxygen supply limits the burning, so unburnt pyrolysis gases can build up, and mixed with oxygen they form a flammable mixture that needs only ignition energy.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref> A [[Backdraft]] is the explosive ignition of such gases when fresh air suddenly enters, for example when a door is opened, and it can produce a large fireball or a jet of flame. Van Rossum describes it as a dangerous phenomenon for the fire service.<ref name="VR-4.9">Van Rossum (2027), §4.9.</ref>

A [[smoke explosion]] is a different event. It is the very rapid burning of flammable gases that are already reasonably premixed with air within their explosion limits, set off by a spark, by glowing particles or by self-ignition.<ref name="VR-4.10">Van Rossum (2027), §4.10.</ref> The Dutch basic principles favour keeping a building closed where possible, which they call anti-ventilation, and controlling the doors during an interior attack.<ref name="NIPV-63" />

Ventilation, smoke control and sprinklers also affect one another. The NIPV study notes that smoke and heat removal can raise the chance of a successful interior attack in indoor car parks.<ref name="NIPV-6">Van der Graaf et al. (2021/2023), p. 6.</ref> Building ventilation systems that keep running during a fire, or that recirculate air, can themselves spread smoke through the building.<ref name="Evans-70">Evans et al. (2005), p. 70.</ref> Sprinkler sprays can also cool the heat-sensitive links of downstream sprinklers and smoke vents and delay their opening, effects known as sprinkler skipping and vent skipping.<ref name="Cooper-3-239">Cooper (2002b), p. 3-239.</ref>

== Firefighting in building design and regulation ==

The International Fire Engineering Guidelines state that evacuation analysis should not rely on fire service intervention, although the needs of fire services must not be discounted.<ref name="IFEG-1.9-1" /> In New Zealand, C/VM2 (second edition, 2025) sets out a design scenario for firefighting operations. It sets requirements for access, water supply, information for firefighters and structural stability.<ref name="CVM2-53" /> For large unsprinklered firecells near a boundary, it sets limits for the moment when firefighters first apply water. The radiation at 1.5 m above the floor may then not exceed 4.5 kW/m², and the smoke layer must be at least 2 m above the floor.<ref name="CVM2-53" /> That moment may be taken as 1,200 s, or 1,000 s with a fire alarm connected directly to a remote receiving centre.<ref name="CVM2-54">Ministry of Business, Innovation and Employment (2025b), p. 54.</ref>

In Australia, the Fire Safety Verification Method Standard 2022 includes a fire brigade intervention scenario, assessed with the Fire Brigade Intervention Model, that applies to buildings within 50 km road travel of a fire station.<ref name="FSVM-15">Australian Building Codes Board (2022), p. 15.</ref> The 2020 handbook shows how a design fire may be cut short by occupants, by sprinklers, or by fire brigade suppression before or after flashover.<ref name="ABCBH-61" /> The design fire is then modified for the automatic or fire brigade intervention that applies to the scenario.<ref name="ABCBH-61" />

In the Netherlands, an equivalent solution under the 2012 Building Decree cannot take credit for a fire service attack.<ref name="NIPV-15">Van der Graaf et al. (2021/2023), p. 15.</ref> The NIPV study stresses that the fire service has an obligation of best efforts rather than of result.<ref name="NIPV-41">Van der Graaf et al. (2021/2023), p. 41.</ref> Some Dutch design curves do include firefighting: the car fire curve in the car park standard NEN 6098, as described by Van Rossum, reflects the extinguishing action of the fire service.<ref name="VR-8.6" />

== Limits and common misconceptions ==

Putting out the visible flames does not always end a fire. Glowing combustion inside solids can survive a gaseous agent and re-ignite when air returns, and a damaged foam blanket can let a liquid fire burn back.<ref name="NUREG-B43" /><ref name="NUREG-B60" /> Battery packs of electric vehicles can catch fire again shortly after the flames are out. They therefore need continuous cooling and temperature monitoring, for example in a water-filled immersion container.<ref name="NIPV-46">Van der Graaf et al. (2021/2023), p. 46.</ref>

More agent is not automatically better. Water can spread a burning liquid that floats on it, and repeated discharges of dry chemical at Point Beach left residue across the containment building without putting the fire out.<ref name="Fleming-4-72" /><ref name="NUREG-H29" /> In enclosed spaces, dry chemical can also impair breathing and reduce visibility.<ref name="NUREG-H29" /> Firefighting itself exposes firefighters to heat, flame, smoke, explosion and structural collapse, as one of the US definitions of fire suppression states.<ref name="NUREG-F29" />

Engineering models cannot promise what firefighters will find. The International Fire Engineering Guidelines note that the effect of fire service activities does not lend itself easily to quantification, so many aspects rest on qualitative judgement.<ref name="IFEG-2.9-2">National Research Council of Canada et al. (2005), p. 2.9-2.</ref> C/VM2's limits apply only at the moment firefighters first apply water, and operations after that depend on the conditions they face at the time.<ref name="CVM2-54" />

== See also ==

* [[Hose reel]]
* [[Rollover]]
* [[Electric vehicle fire]]
* [[Critical water application rate]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board. (2020b). ''Handbook: Fire Safety Verification Method'' (Print version 1.1).
* Australian Building Codes Board. (2022). ''Fire Safety Verification Method Standard 2022''.
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* Cooper, L. Y. (2002b). Smoke and heat venting. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-219–3-242). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Hopkins, M., Schoenrock, J., & Budnick, E. (2005). ''Fire suppression systems'' (NIST NCSTAR 1-4B). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Ministry of Business, Innovation and Employment. (2025b). ''Verification Method C/VM2: Framework for fire safety design'' (2nd ed.).
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-88–4-122). National Fire Protection Association; Society of Fire Protection Engineers.
* Siu, N. (2002). Fire risk assessment for nuclear power plants. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 5-214–5-226). National Fire Protection Association; Society of Fire Protection Engineers.
* Van der Graaf, J., Hessels, T., & Rosmuller, N. (2023). ''Fire safety of indoor car parks accommodating electrically powered vehicles''. Nederlands Instituut Publieke Veiligheid. (Original work published 2021)
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Firefighting & Fire Service]]

Hand extinguisher

2026-11-02T18:01:48Z

Mark: Redirect to Fire extinguisher (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire extinguisher]]

Portable extinguisher

2026-11-02T18:01:41Z

Mark: Redirect to Fire extinguisher (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire extinguisher]]

Portable fire extinguisher

2026-11-02T18:01:35Z

Mark: Redirect to Fire extinguisher (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire extinguisher]]

Fire extinguisher

2026-11-02T18:01:23Z

Mark: Revise against the FSE wiki writing guidelines: verified and corrected citations, labelled US and NZ requirements, See also, links, style (revised by Claude Opus 5.5)

A '''fire extinguisher''' is a portable device, carried by hand or on wheels, that holds a limited supply of extinguishing agent for attacking a fire while it is still small.<ref name="SH126">Scheffey and Hickey (2002), p. 4-126.</ref><ref name="G155">Grant (2002), p. 4-155.</ref> Extinguishers contain water, foam, dry chemical powder, carbon dioxide, wet chemical solutions or halon. Each [[Extinguishing agent]] works in its own way and suits some fires better than others.<ref name="ISB15">Iqbal and Salley (2004), p. B-15.</ref><ref name="ISB16">Iqbal and Salley (2004), p. B-16.</ref> In the United States, the rating on an extinguisher combines a number for its relative effectiveness with letters for the [[Fire classes]] on which it was found to be effective.<ref name="ISF25">Iqbal and Salley (2004), p. F-25.</ref>

Extinguishers belong to manual fire suppression, which people carry out with portable extinguishers, hoses or manually operated fixed systems.<ref name="ISF29">Iqbal and Salley (2004), p. F-29.</ref> A report of the US Nuclear Regulatory Commission describes a fire in its earliest stage as one that portable extinguishers or small hoses can still control without protective clothing or breathing apparatus.<ref name="ISF38">Iqbal and Salley (2004), p. F-38.</ref> Incident reviews describe fires that defeated several extinguishers but were then put out quickly with water.<ref name="ISH21">Iqbal and Salley (2004), p. H-21.</ref><ref name="ISH29">Iqbal and Salley (2004), pp. H-29–H-30.</ref> Fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they are specially trained.<ref name="IFEG177">National Research Council of Canada et al. (2005), p. 1.7-7.</ref>

== How an extinguisher works ==

An extinguisher stores its agent under pressure, or together with a gas that drives it out. Dry chemical powder consists of fine particles coated to prevent caking, and an inert gas projects the powder onto the fire.<ref name="ISB55">Iqbal and Salley (2004), p. B-55.</ref> Carbon dioxide is stored as a gas liquefied under pressure and provides its own pressure for release.<ref name="ISB41">Iqbal and Salley (2004), p. B-41.</ref> A portable extinguisher with aqueous film-forming foam closely resembles a stored-pressure water extinguisher, except for its special nozzle.<ref name="SH126" />

Sizes vary widely. Aqueous film-forming foam extinguishers are usually available as hand-portable models of 9 litres and as wheeled models holding 125 litres.<ref name="SH126" /> The supply of agent is limited. At one US nuclear power plant, three portable extinguishers together discharged about 32 kg (70 pounds) of dry chemical on a small fire of rags and debris.<ref name="ISH29" />

The technology has changed over time. Carbon tetrachloride became available as early as 1907 and was used mostly in hand-pump portable extinguishers, because it conducted little electricity and left no residue. It caused a number of accidental deaths and serious injuries through its toxicity, and its use was halted during the 1950s.<ref name="G150">Grant (2002), p. 4-150.</ref> Methyl bromide, a more effective agent discovered in the late 1920s, was never used in portable extinguishers because of its high toxicity.<ref name="G150" />

Chemical foam extinguishers, in which a reaction between sodium bicarbonate and aluminium sulphate produced the foam and pushed it out, are now generally regarded as obsolete. Their manufacture in the United States stopped in 1969, and the National Fire Protection Association (NFPA) recommends replacing them.<ref name="ISB63">Iqbal and Salley (2004), p. B-63.</ref><ref name="SH126" /> The US Army also introduced portable extinguishers with halon 1301. Under the Montreal Protocol, however, the production of halons in the developed countries ended on 31 December 1993.<ref name="G151">Grant (2002), p. 4-151.</ref><ref name="DN173">DiNenno (2002), p. 4-173.</ref>

== Agents and what they do ==

NUREG-1805, a report of the US Nuclear Regulatory Commission, names four ways to put out a fire. They are separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or flame, and adding chemicals that change the combustion chemistry. More often several of these act at once.<ref name="ISB15" /> Water cools a burning solid, so that it gives off less flammable gas, and cools the flame.<ref name="ISB15" /> It is the most commonly used extinguishing agent, mainly because it is widely available and inexpensive and absorbs a great deal of heat as it turns into steam.<ref name="FL72">Fleming (2002), p. 4-72.</ref>
[[File:fse-fire-extinguisher-v1.svg|thumb|upright=1.5|alt=Portable agents cool, blanket, coat, inhibit chemistry or reduce oxygen.|Portable extinguishers use several different extinguishing mechanisms. Based on Iqbal and Salley (2004), pp. B-15–B-16.]]

Water also has clear limits. It is unsuitable for certain water-reactive materials, with which it can produce heat, flammable or toxic gases, or explosions.<ref name="FL72" /> Burning hydrocarbon fuels float on water and keep burning, and water under very hot oil turns to steam and throws out burning oil.<ref name="FL72" /><ref name="ISB58">Iqbal and Salley (2004), p. B-58.</ref> [[Firefighting foam]] overcomes the floating problem by forming a layer on the liquid that keeps out air and stops the fuel from evaporating.<ref name="SC88">Scheffey (2002), p. 4-88.</ref> Foam is water-based, however, so it shares the risk of electric shock from live equipment.<ref name="ISB60">Iqbal and Salley (2004), p. B-60.</ref>

Dry chemical powders are very common in manual extinguishers, and their most common use is on relatively small flammable liquid fires.<ref name="ISB56">Iqbal and Salley (2004), p. B-56.</ref> Common types include sodium bicarbonate, potassium bicarbonate and monoammonium phosphate, which is known as "ABC" or multipurpose powder.<ref name="ISB55" /> The powders probably act mainly by removing reactive chemical species from the flame, and they also absorb heat and block radiation.<ref name="ISB56" /> Monoammonium phosphate also forms a glassy coating over the burning surface, which makes it the only common powder considered effective against deep-seated fires.<ref name="ISB56" />

Carbon dioxide is an electrically non-conductive inert gas that is suitable for Class B and Class C fires. It puts out a fire by lowering the concentration of oxygen, of fuel vapour or of both until combustion stops.<ref name="ISF12">Iqbal and Salley (2004), p. F-12.</ref> It has a long history as an extinguishing agent, mainly for flammable liquid fires and fires in electrical equipment.<ref name="ISB41" /> Wet chemical agents, solutions of water with potassium carbonate, potassium acetate or potassium citrate, are listed in NUREG-1805 for cooking oil and fat fires.<ref name="ISF70">Iqbal and Salley (2004), p. F-70.</ref><ref name="ISB16" />

== Classes and ratings ==

The fire classes used in the United States come from NFPA 10, Standard for Portable Fire Extinguishers. Its 2002 edition, as summarised in NUREG-1805, has five classes. Class A covers ordinary combustibles such as wood, paper and many plastics, Class B flammable liquids and gases, and Class C energised electrical equipment. Class D covers combustible metals, and Class K cooking appliances with vegetable or animal oils and fats.<ref name="NFPA10">National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-13.</ref> The halon chapter of the SFPE Handbook of Fire Protection Engineering (third edition, 2002) shows only four classes, A to D, so the letters depend on the document and its edition.<ref name="G153">Grant (2002), p. 4-153.</ref>

The rating number shows relative effectiveness, and the letters show the classes of fire on which the extinguisher has been found to be effective.<ref name="ISF25" /> Ratings are based on standardised tests developed by Underwriters Laboratories.<ref name="ISF23">Iqbal and Salley (2004), p. F-23.</ref> A hand-portable foam extinguisher of 9 litres, for example, is rated 3A:20B, and a wheeled unit of 125 litres is rated 20A:160B.<ref name="SH126" /> For Class C the rating reflects the non-conductive properties of the agent. Once electrical equipment has been de-energised, extinguishers designed for Class A or Class B fires can be used safely.<ref name="ISB16" /><ref name="NFPA10" />

The class table in NUREG-1805 shows why the letters matter. It states that water and water-based extinguishers should never be used on Class D metal fires, and that a Class D extinguisher must suppress the fire without reacting physically or chemically with the metal.<ref name="ISB16" /> Among the powders, monoammonium phosphate is not recommended for kitchen fires involving hot fat because it is acidic; an alkaline powder such as potassium bicarbonate is preferred.<ref name="ISB56" />

== Role in fire protection ==

Portable extinguishers are one layer among several. The US Nuclear Regulatory Commission's defence-in-depth approach aims to prevent fires, to detect, control and extinguish quickly those that do occur, and to protect safety functions if a fire is not put out promptly.<ref name="IS12">Iqbal and Salley (2004), p. 1-2.</ref> Portable extinguishers form part of the second layer, together with detectors, fixed suppression systems, hose stations, hydrants and fire brigades. The approach recognises that the first two layers are not always entirely successful.<ref name="IS12" />

In the same handbook, Grant gives an example for a computer room in which each stage of a fire has its own control measure. Portable extinguishers, together with an automatic halon system, serve the incipient stage, while automatic sprinklers serve the stage before flashover.<ref name="G155" /> A US fire risk method for nuclear power plants similarly notes that small fires are likely to be put out immediately with portable extinguishers.<ref name="NW1117">Nowlen et al. (2005b), p. 11-17.</ref> A fire has moved beyond this early stage when firefighters need thermal protective clothing or breathing apparatus, or have to crawl to stay below the smoke and heat.<ref name="ISF38" />

Extinguishers and an automatic [[Sprinkler system]] complement each other. NUREG-1805 notes that human response, such as discovering the fire and the travel of a fire brigade, usually takes much longer than the time sprinklers need to control a fire in its early stages.<ref name="IS101">Iqbal and Salley (2004), p. 10-1.</ref> In its study of the World Trade Center, the US National Institute of Standards and Technology (NIST) noted that the sprinklers there were designed to control fires. Manual intervention with hand-held extinguishers or hose lines was generally needed to put out all of the burning, especially in areas shielded from the sprinkler spray.<ref name="EV9">Evans et al. (2005), p. 9.</ref>

In fire engineering design, the International Fire Engineering Guidelines (2005 edition) count manual suppression equipment among the measures for detection, warning and suppression.<ref name="IFEG1210">National Research Council of Canada et al. (2005), p. 1.2-10.</ref> Suppression by building occupants, using extinguishers and [[Hose reel|hose reels]], may be taken into account if appropriate criteria are used.<ref name="IFEG171">National Research Council of Canada et al. (2005), p. 1.7-1.</ref> The guidelines add that it is customary to assume that occupants will not engage in effective firefighting unless they belong to a specially trained site emergency response crew.<ref name="IFEG177" /> Professional [[Firefighting]] by the fire service is treated separately.<ref name="IFEG177" />

== People and training ==

Whether an extinguisher is used depends on the people present. In the SFPE Handbook, Bryan describes how a person who has recognised a fire evaluates the threat. The person then either evacuates the building or fights the fire, for example by fetching an extinguisher or operating a manual fire alarm.<ref name="BR318">Bryan (2002), pp. 3-318–3-319.</ref> People with firefighting training or experience, in surroundings they know, are likely to choose more adaptive actions. In one office building fire, regular occupants fought the fire and alerted others, while visitors attending training sessions mostly evacuated.<ref name="BR318" />

Studies of residential and other fires give an idea of how often people fight fires. In a British study of 2,193 people in 952 fires, 14.7 percent showed firefighting behaviour, against 22.9 percent of 584 people in 335 mainly residential fires in a US study.<ref name="BR322">Bryan (2002), pp. 3-322–3-323.</ref> In the US study, fetching an extinguisher was the first action of 4.6 percent of the participants.<ref name="BR322" />

Trained staff play a larger role in workplaces. In US nuclear power plants, a fire watch is a person who provides extra cover, for example during hot work, or makes up for an impaired fire protection system. Fire watches should be trained to recognise fire hazards, to use fire extinguishers and to follow notification procedures.<ref name="ISF29" /> A US method for counting fire events treats a fire as potentially challenging when a hose stream, several portable extinguishers or a fixed suppression system were needed.<ref name="NWC9">Nowlen et al. (2005b), pp. C-8–C-9.</ref> A hot-work fire also counts if active intervention was needed, even when the fire watch put it out quickly, although the use of a single extinguisher should not be the only indicator.<ref name="NWC9" />

== Requirements and maintenance ==

Requirements for extinguishers depend on the code or standard that applies and on its edition. In the United States, NUREG-1805 lists NFPA 10, Standard for Portable Fire Extinguishers (2002 edition), among the current NFPA standards. It notes that NFPA codes are revised on cycles of 3 to 5 years, so the edition in force at the time of design is the code of record.<ref name="ISE1">Iqbal and Salley (2004), p. E-1.</ref> The SFPE Handbook refers to NFPA 10 for the selection and placement of portable extinguishers.<ref name="SH126" /> Citing NFPA 10 and a handbook chapter on extinguisher use and maintenance, NUREG-1805 describes three hazard levels by the amount of Class A and B materials present. Light hazard can include offices and classrooms, ordinary hazard shops and parking garages, and extra hazard woodworking, vehicle repair and cooking areas.<ref name="ISB14">Conroy (1997) and National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-14.</ref>

New York City shows how requirements can sit in different documents. NIST found that the New York City Building Code had no requirements for fire extinguishers, because it required occupant hose reels instead.<ref name="LEW151">Lew et al. (2005), p. 151.</ref> For the World Trade Center, the Port Authority nevertheless required portable extinguishers in all spaces. It followed a Fire Department of New York directive of 17 September 1980 and section 27-4009 of the New York City Fire Prevention Code of 1 July 1988.<ref name="GJ17">Grill and Johnson (2005c), p. 17.</ref>

Maintenance is part of [[Fire safety management]]. The International Fire Engineering Guidelines state that active fire protection equipment, including suppression equipment, needs particular attention to ensure proper installation, commissioning, management and use. Its maintenance should follow the relevant codes, standards and manufacturer's literature.<ref name="IFEG178">National Research Council of Canada et al. (2005), p. 1.7-8.</ref> The New Zealand part of the guidelines adds that the fire safety of a building depends on the ongoing functioning of its fire safety system. Inspection, testing and maintenance programmes should therefore have due regard to New Zealand standards and legislation.<ref name="IFEGNZ">National Research Council of Canada et al. (2005), p. 0.3-8 (Part 0, New Zealand).</ref> Among the information notices of the Nuclear Regulatory Commission listed in NUREG-1805 is one of 11 April 2001 titled "Neglected Fire Extinguisher Maintenance Causes Fatality".<ref name="ISD14">Iqbal and Salley (2004), p. D-14.</ref>

== Limits, side effects and incident experience ==

Dry chemical powder has side effects. Its sudden release and unexpected re-ignition of the fire are hazards, and although the powders are non-toxic, they can cause temporary breathing difficulty and reduce visibility.<ref name="ISB57">Iqbal and Salley (2004), p. B-57.</ref> All powders need significant cleaning after use, and some corrosion or damage is possible.<ref name="ISB56" /> Powders become sticky when heated, and applying water to the residue speeds up the corrosion of equipment.<ref name="ISH29" />

At the Point Beach 1 nuclear power plant in 2001, three portable dry chemical extinguishers failed to put out a small fire, which re-ignited twice. The fire brigade then put it out easily with about 57 to 76 litres (15 to 20 gallons) of water from a hose line.<ref name="ISH29" /> White powder covered about half of the containment basement floor, and NUREG-1805 concludes that the cleanup effort called for a more careful choice of extinguishing agent.<ref name="ISH29" />
[[File:fse-fire-extinguisher-v3.svg|thumb|upright=1.5|alt=Powder clouds reduce visibility, coat equipment and require cleanup while hot fuel can reflash.|Extinguishing also creates post-discharge hazards and restoration needs. Based on Iqbal and Salley (2004), pp. H-29–H-30.]]

Fires in energised electrical equipment have repeatedly defeated portable extinguishers in US nuclear power plants. At Waterford 3 in 1995, attacks with carbon dioxide, halon and dry chemical extinguishers failed. Water was permitted only about 90 minutes after the fire started, and the fire was then under control within 4 minutes.<ref name="ISH21" /> At Prairie Island 1 in 2001, more than 20 portable carbon dioxide extinguishers were used over about 1.5 hours on a breaker fire, and two fire brigade members were treated for heat exhaustion.<ref name="ISH30">Iqbal and Salley (2004), pp. H-30–H-31.</ref> A review of high-energy arcing faults in electrical switchgear notes that in severe events the first extinguishers may be ineffective whatever the agent, and that such fires were finally put out with water.<ref name="NWM3">Nowlen et al. (2005b), p. M-3.</ref>

Delivery is a further limit. In a deep-seated fire, [[Smouldering]] continues below the surface, where an agent cannot easily reach the seat of the fire.<ref name="ISB39">Iqbal and Salley (2004), pp. B-39–B-40.</ref> A gaseous agent can put out the visible flames at once while glowing combustion continues inside, and the fire can then re-ignite when air returns.<ref name="ISB43">Iqbal and Salley (2004), p. B-43.</ref> Low-expansion foam works well on a flat pool fire but is not particularly effective on running fuel or a pressurised spray.<ref name="SC88" />
[[File:fse-fire-extinguisher-v2.svg|thumb|upright=1.5|alt=Extinguisher discharge reaches a pool but leaves shielded and deep fuel hot.|Manual extinguishing depends on delivery, coverage and remaining fuel condition. Based on Scheffey (2002), p. 4-88 and Iqbal and Salley (2004), pp. B-43–B-44.]]

Gaseous agents also have hazards of their own. [[Carbon dioxide]] replaces the oxygen in the air, and people become unconscious at a concentration of 10 percent by volume.<ref name="ISB41" /> Grant notes that the high concentrations needed to extinguish a fire with carbon dioxide make the protected space lethal to people.<ref name="G155" /> In battery rooms with lead-acid batteries, NUREG-1805 advises against discharging an extinguisher directly onto a battery, because the thermal shock may crack its case or cover.<ref name="IS1611">Iqbal and Salley (2004), p. 16-11.</ref>

== See also ==

* [[Hot work]]
* [[Dry and wet risers]]
* [[Fire hydrant]]

== Notes ==

<references />

== References ==

* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* DiNenno, P. J. (2002). Halon replacement clean agent total flooding systems. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-173–4-200). National Fire Protection Association; Society of Fire Protection Engineers.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Grant, C. C. (2002). Halon design calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-149–4-172). National Fire Protection Association; Society of Fire Protection Engineers.
* Grill, R. A., & Johnson, D. A. (2005c). ''Post-construction modifications to fire protection and life safety systems of the World Trade Center towers'' (NIST NCSTAR 1-1H). National Institute of Standards and Technology.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-88–4-122). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L., & Hickey, H. E. (2002). Foam system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-123–4-148). National Fire Protection Association; Society of Fire Protection Engineers.

[[Category:Firefighting & Fire Service]]

Fire experience data

2026-11-02T17:54:26Z

Mark: Redirect to Fire statistics (FSE wiki, revised by Claude Opus 5.5)

#REDIRECT [[Fire statistics]]