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Fire testing

2026-11-02T18:02:44Z

Thomas: Improve Fire testing: sourced explanations, calculations and internal links (Codex)

'''Fire testing''' is the controlled evaluation of materials, products, components or systems under specified fire or thermal exposure. Tests provide measurements such as ignition time, heat release rate, mass loss, flame spread, smoke production and fire resistance. Their purpose is to characterise response under defined conditions rather than to reproduce every possible real fire.<ref name="Janssens-3-38">Janssens (2002), pp. 3-38–3-39.</ref><ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

Tests range from bench-scale material measurements to full-scale product and system experiments. Each scale addresses different controlling processes, including material decomposition, room feedback, ventilation and installation geometry. Results should therefore be applied only with a suitable model and a clear account of the test arrangement.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="Babrauskas-3-3" />

Fire testing supports [[Reaction to fire]] and [[Fire resistance test]] assessments, design data, product comparison and model validation. It also reveals uncertainty from apparatus, specimen preparation, instrumentation and real-world variability.<ref name="Janssens-3-38" /><ref name="Babrauskas-3-33">Babrauskas (2002), pp. 3-32–3-33.</ref>

== Purposes and measurements ==

A test can establish whether and how a material ignites, how quickly it releases energy, how a flame spreads and how much smoke or toxic product is generated. Other tests evaluate whether a construction maintains integrity, insulation or structural adequacy. These are different performance questions and require different endpoints.<ref name="CVM2-64">Ministry of Business, Innovation and Employment (2025), p. 64.</ref><ref name="Milke-4-209">Milke (2002), p. 4-209.</ref>

Heat release rate is central to many reaction-to-fire methods because it links material consumption with fire severity. Effective heat of combustion connects heat release and mass loss but can vary during a test. Bomb-calorimeter values alone therefore cannot represent all real burning behaviour.<ref name="Janssens-3-39">Janssens (2002), p. 3-39.</ref><ref name="Babrauskas-3-1" />

Smoke and toxic-product measurements add further dimensions. Soot yield affects optical density, while carbon monoxide and other species influence inhalation hazard. Their yields vary with combustion mode, so test ventilation and exposure must be reported.<ref name="Mulholland-2-259">Mulholland (2002), p. 2-259.</ref><ref name="Purser-2-96">Purser (2002), p. 2-96.</ref>

Tests can also provide model inputs. A heat-release curve, ignition criterion or material property can support calculations for a larger scenario, but the model still needs to represent scale, enclosure and installation. A measured result does not eliminate modelling assumptions.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

== Bench-scale calorimetry ==

The [[Cone calorimeter]] exposes a small specimen to controlled radiant heat and measures heat release rate by oxygen consumption. Its conical heater, spark ignitor, specimen holder and load cell sit beneath a hood and exhaust duct. Air and combustion products are extracted while oxygen and other gas concentrations are measured.<ref name="Janssens-cone">Janssens (2002), p. 3-55.</ref>

The standard specimen is 0.1 m by 0.1 m, with horizontal and vertical orientations possible. Maximum irradiance can exceed 100 kW/m², and the heater can be positioned above or beside the specimen. The initial exhaust flow can be adjusted between 10 and 32 litres per second, with relatively constant volumetric flow during a test.<ref name="Janssens-cone" />
[[File:fse-fire-testing-v1.svg|thumb|upright=1.5|alt=Cone heater, specimen, spark, load cell and exhaust gas analysis in a cone calorimeter.|Cone-calorimeter setup and oxygen-consumption measurement. Based on Janssens (2002), p. 3-55.]]

Oxygen-consumption calorimetry estimates heat release from oxygen used, commonly using 13.1 MJ per kilogram of oxygen consumed. Corrections can be needed for carbon monoxide and for substances whose oxygen-consumption constant differs. This is a measurement method, not a universal conversion from mass loss alone.<ref name="Drysdale-1-96">Drysdale (2002), pp. 1-95–1-96.</ref><ref name="Babrauskas-3-33" />

Bench-scale tests are efficient for comparing materials and obtaining input curves, but specimen size and boundary conditions differ from installed products. Orientation, backing, thickness and mounting can change heat feedback and decomposition. Application to a full object requires those differences to be evaluated.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

=== Converting oxygen consumption to power ===

Oxygen-consumption calorimetry estimates released heat from the oxygen consumed by combustion. Drysdale gives an approximate conversion of 13.1 MJ per kilogram of oxygen for many common fuels. The basic relationship multiplies oxygen-consumption rate by that energy per unit mass.<ref name="Drysdale-1-96" />
<math display="block">\dot Q\approx E_{\mathrm{O_2}}\dot m_{\mathrm{O_2,consumed}}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot Q</math> || Heat release rate || kW
|-
| <math>E_{\mathrm{O_2}}</math> || Energy released per mass of oxygen consumed; approximately 13,100 || kJ/kg
|-
| <math>\dot m_{\mathrm{O_2,consumed}}</math> || Oxygen consumption rate || kg/s
|}

For a 1 MW full-scale source, this simplified conversion gives 1,000/13,100 = 0.0763 kg/s of oxygen consumed. The calculation illustrates the principle at an item-fire scale; it is not a heat-release claim for a small cone-calorimeter specimen. The assumed conversion and the measured oxygen deficit must use compatible units.<ref name="Drysdale-1-96" /><ref name="VR-4.6">Van Rossum (2027), §4.6.</ref>

An oxygen concentration alone does not give this mass-consumption rate. The instrument also needs the exhaust flow and the incoming-air reference, with corrections appropriate to the apparatus and gas measurements. Incomplete combustion, including carbon-monoxide production, can require corrections to the simple heat-per-oxygen relation.<ref name="Drysdale-1-96" /><ref name="Janssens-3-38" />

Janssens describes the cone calorimeter with a 0.1 m × 0.1 m specimen under controlled irradiation. The measured heat release per specimen area can support comparisons between materials at that exposure. It does not by itself determine the burning area, ventilation or thermal feedback of a complete room fire.<ref name="Janssens-cone" /><ref name="Babrauskas-3-3" />

== Single Burning Item and room tests ==

The [[Single Burning Item test]] (SBI) uses two wall panels in a corner configuration without a ceiling and is a regulatory heat-release test for building products. It evaluates product response under that specified exposure. Results should not be interpreted as direct measurements of every wall or room installation.<ref name="Babrauskas-SBI">Babrauskas (2002), p. 3-32.</ref>

A [[Room corner test]] places materials in a small enclosure with a defined burner and opening, then collects combustion products in a hood and exhaust duct. It includes hot-layer and room-surface feedback that open-burning tests omit. This makes it useful when enclosure effects are expected to influence heat release.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-1" />
[[File:fse-fire-testing-v2.svg|thumb|upright=1.5|alt=Two wall panels in an open corner and a burner in a room with a hot upper layer.|SBI and room-corner tests represent different boundary conditions. Based on Babrauskas (2002), p. 3-33 and Janssens (2002), p. 3-39.]]

Room tests can differ from open calorimetry as fire grows. Babrauskas reports limited augmentation for some upholstered chairs at lower heat release rates, but much stronger effects for mattresses and liquid pools. A single room correction is therefore not valid for every product.<ref name="Babrauskas-3-2">Babrauskas (2002), p. 3-2.</ref>

Room-fire data also cannot be extrapolated directly to rooms with larger ventilation. Open-burning data may instead suit well-ventilated conditions when the fuel package is comparable. The source test and intended enclosure must be matched explicitly.<ref name="Babrauskas-3-2" />

== Large-scale and system tests ==

A [[Large-scale facade fire test]] evaluates facade systems at a scale where joints, cavities, cladding layers and external flames can interact. Such tests are relevant to system behaviour that cannot be inferred reliably from small material specimens. The actual method and installation remain necessary when applying the result.<ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref><ref name="CVM2-64" />

Fire-resistance tests expose structural and separating assemblies to a defined furnace curve. Milke explains that ASTM E119 addresses structural integrity, temperature, flame and hot-gas passage and, in some cases, hose-stream response. These criteria are distinct from reaction-to-fire measurements of a material's own combustion.<ref name="Milke-4-209" /><ref name="Milke-4-210">Milke (2002), pp. 4-209–4-210.</ref>

Large tests can still be comparative rather than literal full-scale reproductions. Furnace dimensions, loading and end restraints may differ from the built structure. Actual performance requires appropriate analytical extension and validation rather than assuming the test building is identical.<ref name="Milke-4-210" />

C/VM2 (second edition, 2025) determines fire resistance ratings from standard tests or calculation methods verified by experimental data from standard tests. Its ratings report structural adequacy, integrity and insulation in that order. This is a regulatory use of fire-test evidence within New Zealand.<ref name="CVM2-64" />

== Data quality and uncertainty ==

Measurement uncertainty includes bias and random error. Calibration with a metered high-purity gas can reduce bias in oxygen-consumption systems, while interlaboratory trials help quantify random error. The 95% confidence intervals reported for some tests should be retained when comparing results.<ref name="Babrauskas-3-33" />
[[File:fse-fire-testing-v3.svg|thumb|upright=1.5|alt=Calibration addresses bias, repeated trials show random error and a model adds extrapolation uncertainty.|Fire-test uncertainty comes from measurement and application. Based on Babrauskas (2002), pp. 3-32–3-33.]]

Apparatus features influence results. Heater spectrum and orientation, specimen mounting, exhaust flow and gas analysis can all affect the measured curve. Using different methods without checking those features can produce apparent material differences that are really method differences.<ref name="Janssens-3-56">Janssens (2002), p. 3-56.</ref><ref name="Janssens-3-39" />

Specimen selection adds uncertainty. Composite products may have varying layers, moisture and manufacturing quality, and a small specimen may not represent the whole. Full-scale tests reduce some of these issues but introduce cost, ventilation and installation variability.<ref name="Babrauskas-3-3" /><ref name="Kodur-Harmathy-1-156">Kodur and Harmathy (2002), p. 1-156.</ref>

Data should include the complete time history and its definitions. Peak heat release rate, an early average and a long-term average answer different questions, and their values need not agree. The averaging interval and ignition reference must be stated.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-56" />

== Using results in engineering ==

Results can support material comparison, regulatory classification and design-fire selection. The intended use determines which measurements and acceptance criteria matter. A test that suits one purpose may not provide the data needed for another.<ref name="CVM2-52">Ministry of Business, Innovation and Employment (2025), p. 52.</ref><ref name="Janssens-3-39" />

For reaction-to-fire assessment, heat release, ignition, spread and smoke describe how a product contributes to fire. For fire resistance, the construction's ability to continue separating or supporting loads is central. Confusing these measures can lead to incorrect claims about a material or assembly.<ref name="CVM2-64" /><ref name="Milke-4-209" />

For modelling, bench-scale data can be extrapolated only with a defensible model. Full-scale data are stronger evidence when they match the actual fuel package and enclosure, but even then installation and ventilation differences need review. Similar product names are not enough.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-39" />

For regulatory use, the applicable standard and edition must be identified. C/VM2 uses its 2025 second edition and New Zealand context, while ASTM E119 and ISO room tests have their own methods and criteria. A class or rating should not be transferred between systems without demonstrating equivalence.<ref name="CVM2-64" /><ref name="Milke-4-210" />

== Limits and common misunderstandings ==

A fire test does not prove performance in every real fire. It proves response under the reported exposure and arrangement. Extrapolation needs a model, compatible conditions and acknowledgment of uncertainty.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-39" />

A larger test is not automatically a better test. Scale can introduce important room and system feedback, but it can also make results harder to reproduce and apply elsewhere. The appropriate scale depends on the decision and the controlling mechanisms.<ref name="Babrauskas-3-2" /><ref name="Janssens-3-39" />

A standard test is not a universal measure of noncombustibility or safety. It characterises particular properties, and other hazards such as toxicity, installation and changing ventilation may remain. All relevant performance criteria should be considered.<ref name="Purser-2-96" /><ref name="CVM2-64" />

test data are not free of error merely because they follow a standard. Calibration, specimen preparation, instrument response and averaging still matter. These details belong with the data used for design or publication.<ref name="Babrauskas-3-33" /><ref name="Janssens-3-56" />

== Test selection and review ==

Test selection should begin with the decision and its controlling mechanisms. Material-level ignition and heat release may be sufficient for a simple comparison, but an enclosure or assembly can introduce new feedback. The test should include those mechanisms without adding irrelevant complexity.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

A test plan should specify the specimen, exposure, instrumentation and endpoint before testing. Mounting, backing, moisture, orientation and pilot location can all change the result. Recording these choices makes the resulting data reproducible and helps prevent an incorrect comparison with another method.<ref name="Janssens-3-56" /><ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref>

The exposure should be characterised as a time history where relevant. A constant radiant panel, a furnace curve and a developing compartment fire produce different boundary conditions. Using the first two as though they were interchangeable with the third would hide important transient behaviour.<ref name="Lie-4-201">Lie (2002), pp. 4-201–4-203.</ref><ref name="VR-5.1">Van Rossum (2027), §5.1.</ref>

Instrumentation should match the quantity required. Load cells measure mass loss, gas analysers measure species, exhaust measurements support oxygen-consumption calculations, and temperature and heat-flux instruments describe exposure. No one instrument supplies all of those outputs reliably without supporting measurements.<ref name="Janssens-3-56" /><ref name="Babrauskas-3-33" />

A test series can examine sensitivity rather than produce only one result. Changing heat flux, orientation, backing or ventilation reveals whether a conclusion remains stable. Those variations also identify the conditions under which extrapolation to the intended installation becomes uncertain.<ref name="Quintiere-2-247">Quintiere (2002), p. 2-247.</ref><ref name="Babrauskas-3-3" />

Interlaboratory comparison adds another check. It can reveal apparatus, operator and analysis differences that a single-laboratory procedure would miss. Confidence intervals should be reported alongside the measured curve so that small differences between products are not overinterpreted.<ref name="Babrauskas-3-33" />

Validation should compare like with like. A bench-scale heat-release curve should not be compared directly with a room-fire curve without accounting for enclosure feedback, and a layer-average temperature should not be compared directly with a near-ceiling reading. Definitions must match before agreement can be assessed.<ref name="Babrauskas-3-1" /><ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

A final report should separate measurement, calculation and acceptance. It states what was observed, which conversions were applied and which criterion was used to judge performance. This keeps the test result traceable when it is later used for classification, modelling or a design decision.<ref name="Janssens-3-39" /><ref name="CVM2-64" />

The [[Euroclass system]] illustrates why a test must be read through its regulatory method. A result becomes a classification only after the applicable procedures and criteria are applied, and another framework can use different evidence. The underlying measurement should not be assigned a class from an unrelated system without an equivalence assessment.<ref name="Janssens-3-38" /><ref name="CVM2-52" />

Acceptance criteria should be checked against the test's actual output. A furnace endpoint may be a temperature, a heat-release threshold, a spread observation or a retained structural function. Using the wrong endpoint can make a successful measurement answer an unsuccessful design question.<ref name="CVM2-64" /><ref name="Milke-4-210" />

For product comparison, uncertainty should be included when differences are small. Calibration and specimen variation can create differences of the same order as the apparent product effect. Repeating the exposure or comparing independent laboratories can show whether the ranking persists.<ref name="Babrauskas-3-33" /><ref name="Janssens-3-56" />

For design, the complete evidence chain should be documented. It links the tested specimen and exposure to the conversion, model and acceptance criterion used in the building. Any weak link can change the conclusion even when the original measurement is sound.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

A final review should also state which hazards were outside the test. Limited smoke, toxicity, ageing, installation damage and altered ventilation may not be represented. A fire-test result should therefore be used for the properties it measures, not as a guarantee of complete fire safety.<ref name="Purser-2-96" /><ref name="Kodur-Harmathy-1-156" />

The test's role in the wider evidence chain should also be explicit. A result can support a classification, supply a model input or validate a predicted response, but those uses have different evidence requirements. A measurement that is adequate for one role may be incomplete for another.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

== See also ==

* [[Froude scaling]]
* [[Heat release rate]]
* [[Combustibility]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Janssens, M. (2002). Calorimetry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Lie, T. T. (2002). Fire temperature-time relations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Milke, J. A. (2002). Analytical methods for determining fire resistance of steel members. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.). New Zealand Government.
* Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Materials & Fire Testing]]

Flame retardant

2026-11-02T17:59:14Z

Thomas: Improve Flame retardant: sourced explanations, calculations and internal links (Codex)

A '''flame retardant''' is a substance or treatment incorporated in or applied to a material to suppress or delay combustion under specified conditions. It can change ignition, decomposition, heat release, flame spread or residue formation. Its effect is conditional and does not automatically make the treated material noncombustible.<ref name="CVM2-64">Ministry of Business, Innovation and Employment (2025), p. 64.</ref><ref name="Beyler-Hirschler-1-114">Beyler and Hirschler (2002), p. 1-114.</ref>

Flame retardants act through different physical and chemical mechanisms. These include forming an insulating char, reducing heat feedback, changing decomposition pathways and interfering with flame reactions. The appropriate evaluation considers the complete treated product and its fire exposure.<ref name="Beyler-Hirschler-1-114" /><ref name="Grant-4-153">Grant (2002), p. 4-153.</ref>

The treatment can also change smoke and toxic-product yields. Incomplete combustion may produce more carbon monoxide or other hazardous species, while total fuel consumption and fire size may decrease. Fire performance and toxicity therefore require separate assessment.<ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref><ref name="Purser-2-96">Purser (2002), p. 2-96.</ref>

== Purpose and conditions ==

The purpose of a flame retardant is to reduce a material's contribution to fire under the conditions for which it was evaluated. This can mean delayed ignition, lower heat release, slower spread or a different char structure. The claim should identify which of these outcomes was measured.<ref name="CVM2-64" /><ref name="Quintiere-2-247">Quintiere (2002), p. 2-247.</ref>

Specified conditions include heat flux, orientation, specimen form, backing, oxygen supply and exposure duration. A treatment effective in one arrangement can be much less effective in another. Full-scale deformation, joints, ageing and installation can also change performance.<ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref><ref name="White-4-259">White (2002), p. 4-259.</ref>

Additive treatments are incorporated into a material, while reactive treatments are intended to alter its chemistry or response. Surface coatings form another application route. Adhesion and continuity are essential because a damaged or detached layer cannot provide the intended protection.<ref name="Beyler-Hirschler-1-114" /><ref name="White-4-259" />

A flame retardant is not the same as a fire-resistive barrier. It modifies material response, whereas a fire-resistance assessment concerns the performance of a construction in maintaining structural adequacy, integrity or insulation. These measures should not be interchanged.<ref name="CVM2-64" />

== Char-forming and intumescent mechanisms ==

Some flame retardants promote a carbonaceous or intumescent residue. Low-density, porous chars can insulate the underlying material and reduce heat feedback from the flame. Continuity, coherence, adherence, oxidation resistance and permeability determine how useful that barrier remains.<ref name="Beyler-char">Beyler and Hirschler (2002), p. 1-113.</ref>

An [[Intumescent material]] expands or develops a protective layer during heating. This can slow further thermal decomposition considerably and shield virgin material. Volatile products may still have to pass through the char, where secondary reactions can occur.<ref name="Beyler-Hirschler-1-110">Beyler and Hirschler (2002), p. 1-110.</ref><ref name="Beyler-Hirschler-1-114" />
[[File:fse-flame-retardant-v1.svg|thumb|upright=1.5|alt=Expanded char layer reduces heat flow to unburnt material while volatiles escape and char oxidises.|Intumescent residue can insulate but also oxidise. Based on Beyler and Hirschler (2002), pp. 1-110–1-114 and Ohlemiller (2002), p. 2-200.]]

Char formation is not simply cessation of combustion. Carbonaceous char can oxidise at its surface at higher temperatures and sustain glowing or smouldering. Protection therefore depends on limiting both heat transfer and subsequent oxidation of the residue.<ref name="Beyler-Hirschler-1-110" /><ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref>

Inorganic residues can form glassy barriers that reduce volatile escape and protect underlying material. Their effectiveness also depends on continuity and integrity. A cracked or permeable residue can allow heat and oxygen to reach unburnt material.<ref name="Beyler-Hirschler-1-110" />

== Chemical inhibition and other mechanisms ==

Chemical flame retardants can interfere with reactive species in the flame chain reaction. This can increase chain termination relative to branching, reducing flame propagation even when fuel, oxygen and heat remain. The mechanism is represented by the fire tetrahedron rather than by simple fuel removal.<ref name="Grant-4-152">Grant (2002), p. 4-152.</ref><ref name="Simmons-1-150">Simmons (2002), pp. 1-150–1-151.</ref>
[[File:fse-flame-retardant-v2.svg|thumb|upright=1.5|alt=Reactive centres branch until an inhibitor increases termination and the flame stops.|Chemical inhibition interrupts flame chain reactions. Based on Grant (2002), pp. 4-152–4-153 and Simmons (2002), pp. 1-150–1-151.]]

Other treatments change the material's thermal response. A barrier can reduce heat flux, while altered decomposition can change the quantity or composition of volatile fuel. These effects should be distinguished from direct chemical inhibition in the flame itself.<ref name="Beyler-Hirschler-1-114" /><ref name="Beyler-Hirschler-1-112">Beyler and Hirschler (2002), p. 1-112.</ref>

Diluents and inert additives can reduce the proportion of reactive material or absorb energy during heating. Their effect depends on the treated composition and the resulting temperature and burning velocity. A treatment should not be assumed to act through chemistry merely because it reduces measured heat release.<ref name="Simmons-1-150" /><ref name="Beyler-Hirschler-1-112" />

The mechanism determines which measurements are meaningful. Char thickness and integrity matter for a barrier treatment, while flame chemistry and reaction rates matter for an inhibitor. Heat release rate alone cannot identify which mechanism caused an improvement.<ref name="Beyler-Hirschler-1-114" /><ref name="Grant-4-153" />

== Plastics and treated materials ==

[[Plastics in fire]] include thermoplastics, thermosets and elastomers with different physical and chemical responses. Flame retardants can alter those responses, but polymer type, additives and product geometry still control decomposition. A treatment is therefore one component of the complete material system.<ref name="Beyler-Hirschler-1-111">Beyler and Hirschler (2002), p. 1-111.</ref><ref name="Beyler-Hirschler-1-112" />

Thermoplastics can soften and melt before decomposing, while thermosets and cellulosics do not pass through the same fluid state. These transformations can expose new surfaces or disrupt a coating. Treatment performance should be evaluated through those changes rather than only at ambient conditions.<ref name="Beyler-Hirschler-1-112" /><ref name="White-4-259" />

New Zealand's C/VM2, second edition (2025), lists many fire-retardant-treated timbers among its Group Number 2 examples for interior linings. This is an application-specific classification context, not an automatic result for all treated wood. The document requires Group Numbers to be determined through the referenced Building Product Specifications.<ref name="CVM2-linings">Ministry of Business, Innovation and Employment (2025), §§4.7.1.5 and 4.7.2.2, pp. 50–52.</ref>

Wood treatments may delay ignition or reduce surface flame spread without providing the same fire resistance as a protective membrane. White notes that some coated beams showed less improvement in full-scale tests than in earlier small-scale tests, with bending causing adhesion problems. This illustrates the importance of product-scale evaluation.<ref name="White-4-259" />

== Reaction to fire and combustibility ==

[[Reaction to fire]] measurement can show whether a treatment delays ignition, lowers heat release or changes spread. [[Combustibility]] remains the underlying ability to burn under specified conditions, so a treatment can reduce fire contribution without eliminating it. Claims should be framed by the measured outcome.<ref name="Janssens-3-38">Janssens (2002), pp. 3-38–3-39.</ref><ref name="CVM2-64" />

Cone-calorimeter and other controlled tests can compare treated and untreated specimens using consistent exposures. Differences in heat release and mass loss can then be linked to a mechanism where appropriate. Full-scale installation still requires separate evaluation of joints, backing and deformation.<ref name="Janssens-3-39">Janssens (2002), p. 3-39.</ref><ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

A treatment can improve one metric while leaving another unchanged or worse. Slower ignition does not necessarily lower toxic yield, and a thicker char does not necessarily prevent later oxidation. All relevant criteria should be considered before describing overall performance as better.<ref name="Purser-2-96" /><ref name="Ohlemiller-2-200" />

Flame retardants are also not a substitute for ignition-source control, compartmentation or suppression. They address material response, while the wider fire scenario still includes ignition, ventilation and occupants. Their contribution should be assessed as part of that system.<ref name="IFEG-2.4-4">Australian Building Codes Board et al. (2005), p. 2.4-4.</ref><ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>

== Fire toxicity ==

[[Fire toxicity]] can change when a treatment alters combustion efficiency and product composition. Heavily fire-retarded materials can have lower combustion efficiency in Drysdale's cited range, which means more partially oxidised products and less complete energy release. Reduced fire size may offset this, but it does not remove the need to measure yields.<ref name="Drysdale-1-95" /><ref name="Purser-2-96" />

Carbon monoxide, hydrogen cyanide, soot and irritants require separate evaluation. A treatment that suppresses flame can prolong smouldering and alter the dominant exposure period. The resulting atmosphere at an occupied location cannot be inferred from heat release alone.<ref name="Ohlemiller-2-200" /><ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref>

Small-scale yield data need appropriate equivalence ratios and combustion modes. Full-scale vitiated conditions can produce very different products, and material additives can change them further. Toxic assessment should use conditions that represent the intended scenario.<ref name="Purser-2-96" /><ref name="Gottuk-Lattimer-2-54">Gottuk and Lattimer (2002), p. 2-54.</ref>

The treatment itself can also introduce new products into the smoke. Evaluating only the parent polymer may miss additive-related species or interactions. Complete material composition and decomposition chemistry should therefore be considered.<ref name="Purser-2-84">Purser (2002), p. 2-84.</ref><ref name="Purser-2-96" />

== Evaluation and limitations ==

A useful evaluation compares treated and untreated products under the same relevant exposure. It records ignition, heat release, mass loss, residue, smoke and, where needed, structural or separating performance. These results identify which mechanism and claims are supported.<ref name="Janssens-3-39" /><ref name="CVM2-64" />
[[File:fse-flame-retardant-v3.svg|thumb|upright=1.5|alt=Treated material ignites later and forms char before protection fails, while untreated material burns earlier.|Treatment can delay but not eliminate combustion. Based on Beyler and Hirschler (2002), p. 1-114 and White (2002), p. 4-259.]]

The complete product should be tested where practical. Coatings can crack or detach, composites can delaminate and joints can expose untreated regions. White's coated-beam example shows why small-scale success may not persist under full-scale deformation.<ref name="White-4-259" />

Durability and end use also matter. Moisture, ageing, installation and mechanical movement can affect a treatment before any fire begins. Those conditions should be represented or acknowledged when making an application claim.<ref name="White-4-259" /><ref name="Kodur-Harmathy-1-156">Kodur and Harmathy (2002), p. 1-156.</ref>

a flame retardant should not be described as making a material fireproof. It suppresses or delays combustion under specified conditions, and those conditions define the claim. Fire safety still requires appropriate design, installation and assessment of the complete scenario.<ref name="CVM2-64" /><ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref>

== Evidence for treatment performance ==

A treatment assessment should first identify the intended mechanism. A barrier-forming treatment needs evidence of residue continuity and insulation, while a chemical inhibitor needs evidence of changed flame reactions. Measuring only one outcome can leave the actual mechanism uncertain.<ref name="Beyler-Hirschler-1-114" /><ref name="Grant-4-153" />

The control specimen should be as similar as possible to the treated one. Differences in polymer formulation, thickness, backing, moisture and ignition exposure can otherwise be mistaken for a treatment effect. A valid comparison isolates the treatment rather than changing several variables at once.<ref name="Janssens-3-39" /><ref name="Beyler-Hirschler-1-112" />

Thermal decomposition should be followed through the test. A treatment can delay the start of volatile production, change its rate or alter the residue, and each has a different effect on heat release. The point at which protection fails is as important as the initial improvement.<ref name="Beyler-Hirschler-1-114" /><ref name="Beyler-Hirschler-1-110" />

Mechanical condition should be included where it can affect the treatment. White's coated-beam example shows that bending can reduce adhesion and diminish full-scale performance. A flat ambient specimen cannot establish durability under those service conditions.<ref name="White-4-259" />

For smoke assessment, both yield and total mass burned matter. Reduced fuel consumption can lower total effluent, while lower combustion efficiency can increase partially oxidised products per kilogram. The receiver's concentration and exposure time determine which effect dominates.<ref name="Drysdale-1-95" /><ref name="Purser-2-96" />

The residue should be examined after exposure as well as during it. Char can protect underlying material but can also oxidise, crack or detach, exposing the untreated core. A post-fire assessment should therefore include reignition potential and the condition of the remaining barrier.<ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref><ref name="Beyler-Hirschler-1-110" />

Treatment claims should distinguish test evidence from end-use assumptions. A result obtained for one formulation, orientation or exposure does not prove the same performance in every installation. Where those conditions differ, the assessment needs a suitable model or additional testing.<ref name="Babrauskas-3-3" /><ref name="Kanury-2-231" />

A final report should state which outcomes improved and which did not. Delayed ignition, reduced heat release, lower toxicity and maintained structural performance are different claims. Presenting only a general flame-retardant label would hide the conditions and trade-offs that determine actual fire safety.<ref name="CVM2-64" /><ref name="Purser-2-85" />

A treatment should also be reviewed for the point at which its protection is exhausted. Continued heating can consume the char, change its permeability or expose fresh material, so the later heat-release curve may differ sharply from the initial one. The time at which that transition occurs belongs in the assessment.<ref name="Beyler-Hirschler-1-114" /><ref name="Ohlemiller-2-200" />

Alternative outcomes should be reported explicitly when a treatment changes the fire mode. Suppressed flaming can give way to smouldering, which has different particle and toxic-product behaviour and can persist longer. Judging the treatment only by the absence of flame would miss that different exposure pathway.<ref name="Ohlemiller-2-200" /><ref name="Ohlemiller-2-203">Ohlemiller (2002), p. 2-203.</ref>

For toxic assessment, the treatment's complete formulation and combustion history are necessary. Additives can change product composition, while changing oxygen supply can change it again. A constant yield measured under one condition should not be used for the whole fire.<ref name="Purser-2-96" /><ref name="Gottuk-Lattimer-2-55">Gottuk and Lattimer (2002), p. 2-55.</ref>

For separating or structural applications, the treatment should not be credited with fire resistance without assembly evidence. Fire resistance requires structural adequacy, integrity or insulation under defined conditions, which is a different performance claim from delaying combustion. The relevant test and endpoint must be shown.<ref name="CVM2-64" /><ref name="Milke-4-209">Milke (2002), p. 4-209.</ref>

The final claim should therefore be specific about the treatment, the measured improvement and its limits. A statement that combustion is suppressed or delayed can be supported only with the relevant exposure, product and endpoint. Broader claims about noncombustibility, toxicity or structural safety require separate evidence.<ref name="CVM2-64" /><ref name="Babrauskas-3-3" />

An application should also consider whether the treatment changes the meaning of the acceptance criterion. A lower peak heat release can be beneficial for one scenario, while a longer smouldering period can increase exposure duration for another. The evaluation should therefore use the complete time history and the actual performance objective.<ref name="Ohlemiller-2-206" /><ref name="Purser-2-97">Purser (2002), pp. 2-96–2-97.</ref>

For readers, the treatment should be presented as one part of the material's fire response, not as a guarantee. Its mechanism, test evidence, installation requirements and unresolved effects belong together. That allows a flame-retardant claim to be assessed without implying more protection than the evidence supports.<ref name="CVM2-64" /><ref name="Babrauskas-3-3" />

=== A comparison of treated wardrobes ===

Babrauskas reproduces wardrobe tests that distinguish peak heat release from total released energy. The comparison below concerns 3.2 mm plywood wardrobes containing 1.93 kg of clothing and paper. The unpainted and twice-coated specimens had different measured outcomes under those test conditions.<ref name="Babrauskas-wardrobes">Babrauskas (2002), pp. 3-32–3-33, Table 3-1.16.</ref>

{| class="wikitable"
! Specimen !! Peak heat release rate (kW) !! Total released energy (MJ)
|-
| Unpainted wardrobe, test 41 || 6,400 || 590
|-
| Two coats of flame-retardant paint, test 44 || 2,900 || 408
|}

The relative reduction for a measured quantity is the untreated value minus the treated value, divided by the untreated value. Applying that arithmetic separately to power and energy preserves the distinction between the two outcomes.<ref name="Babrauskas-wardrobes" />
<math display="block">R=\frac{X_{\mathrm{untreated}}-X_{\mathrm{treated}}}{X_{\mathrm{untreated}}}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>R</math> || Relative reduction for the selected measurement || dimensionless
|-
| <math>X</math> || Either peak heat release rate or total released energy || kW or MJ, consistently
|}

The peak reduction is (6,400 − 2,900)/6,400, or approximately 55%. The total-energy reduction is (590 − 408)/590, or approximately 31%. A larger reduction in peak power therefore did not mean that the same fraction of the total energy disappeared.<ref name="Babrauskas-wardrobes" />

Both specimens still released substantial heat. The results do not establish that the treated wardrobe was non-combustible, nor that the same coating gives these reductions on another substrate. Thickness, construction, coating application and the imposed exposure belong to the evidence supporting the comparison.<ref name="Babrauskas-wardrobes" />

Mechanical performance can also separate small-scale results from larger assemblies. White reports that bending of coated timber beams caused adhesion problems and reduced the improvement seen in smaller specimens. A coating's insulating action therefore depends partly on whether it remains attached during the relevant deformation and exposure.<ref name="White-4-259" />

== See also ==

* [[Fire testing]]
* [[Soot yield]]
* [[Heat release rate]]
* [[Pyrolysis]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Beyler, C. L., & Hirschler, M. M. (2002). Thermal decomposition of polymers. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Grant, C. C. (2002). Halon design calculations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Janssens, M. (2002). Calorimetry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Milke, J. A. (2002). Analytical methods for determining fire resistance of steel members. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.). New Zealand Government.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Simmons, R. F. (2002). Premixed burning. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* White, R. H. (2002). Analytical methods for determining fire resistance of timber members. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.

[[Category:Materials & Fire Testing]]

Fire testing

2026-11-02T17:59:08Z

Thomas: Improve Fire testing: sourced explanations, calculations and internal links (Codex)

'''Fire testing''' is the controlled evaluation of materials, products, components or systems under specified fire or thermal exposure. Tests provide measurements such as ignition time, heat release rate, mass loss, flame spread, smoke production and fire resistance. Their purpose is to characterise response under defined conditions rather than to reproduce every possible real fire.<ref name="Janssens-3-38">Janssens (2002), pp. 3-38–3-39.</ref><ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

Tests range from bench-scale material measurements to full-scale product and system experiments. Each scale addresses different controlling processes, including material decomposition, room feedback, ventilation and installation geometry. Results should therefore be applied only with a suitable model and a clear account of the test arrangement.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="Babrauskas-3-3" />

Fire testing supports [[Reaction to fire]] and [[Fire resistance test]] assessments, design data, product comparison and model validation. It also reveals uncertainty from apparatus, specimen preparation, instrumentation and real-world variability.<ref name="Janssens-3-38" /><ref name="Babrauskas-3-33">Babrauskas (2002), pp. 3-33–3-34.</ref>

== Purposes and measurements ==

A test can establish whether and how a material ignites, how quickly it releases energy, how a flame spreads and how much smoke or toxic product is generated. Other tests evaluate whether a construction maintains integrity, insulation or structural adequacy. These are different performance questions and require different endpoints.<ref name="CVM2-64">Ministry of Business, Innovation and Employment (2025), p. 64.</ref><ref name="Milke-4-209">Milke (2002), p. 4-209.</ref>

Heat release rate is central to many reaction-to-fire methods because it links material consumption with fire severity. Effective heat of combustion connects heat release and mass loss but can vary during a test. Bomb-calorimeter values alone therefore cannot represent all real burning behaviour.<ref name="Janssens-3-39">Janssens (2002), p. 3-39.</ref><ref name="Babrauskas-3-1" />

Smoke and toxic-product measurements add further dimensions. Soot yield affects optical density, while carbon monoxide and other species influence inhalation hazard. Their yields vary with combustion mode, so test ventilation and exposure must be reported.<ref name="Mulholland-2-259">Mulholland (2002), p. 2-259.</ref><ref name="Purser-2-96">Purser (2002), p. 2-96.</ref>

Tests can also provide model inputs. A heat-release curve, ignition criterion or material property can support calculations for a larger scenario, but the model still needs to represent scale, enclosure and installation. A measured result does not eliminate modelling assumptions.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

== Bench-scale calorimetry ==

The [[Cone calorimeter]] exposes a small specimen to controlled radiant heat and measures heat release rate by oxygen consumption. Its conical heater, spark ignitor, specimen holder and load cell sit beneath a hood and exhaust duct. Air and combustion products are extracted while oxygen and other gas concentrations are measured.<ref name="Janssens-cone">Janssens (2002), p. 3-55.</ref>

The standard specimen is 0.1 m by 0.1 m, with horizontal and vertical orientations possible. Maximum irradiance can exceed 100 kW/m², and the heater can be positioned above or beside the specimen. The initial exhaust flow can be adjusted between 10 and 32 litres per second, with relatively constant volumetric flow during a test.<ref name="Janssens-cone" />
[[File:fse-fire-testing-v1.svg|thumb|upright=1.5|alt=Cone heater, specimen, spark, load cell and exhaust gas analysis in a cone calorimeter.|Cone-calorimeter setup and oxygen-consumption measurement. Based on Janssens (2002), p. 3-55.]]

Oxygen-consumption calorimetry estimates heat release from oxygen used, commonly using 13.1 MJ per kilogram of oxygen consumed. Corrections can be needed for carbon monoxide and for substances whose oxygen-consumption constant differs. This is a measurement method, not a universal conversion from mass loss alone.<ref name="Drysdale-1-96">Drysdale (2002), pp. 1-95–1-96.</ref><ref name="Babrauskas-3-33" />

Bench-scale tests are efficient for comparing materials and obtaining input curves, but specimen size and boundary conditions differ from installed products. Orientation, backing, thickness and mounting can change heat feedback and decomposition. Application to a full object requires those differences to be evaluated.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

=== Converting oxygen consumption to power ===

Oxygen-consumption calorimetry estimates released heat from the oxygen consumed by combustion. Drysdale gives an approximate conversion of 13.1 MJ per kilogram of oxygen for many common fuels. The basic relationship multiplies oxygen-consumption rate by that energy per unit mass.<ref name="Drysdale-1-96" />
<math display="block">\dot Q\approx E_{\mathrm{O_2}}\dot m_{\mathrm{O_2,consumed}}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot Q</math> || Heat release rate || kW
|-
| <math>E_{\mathrm{O_2}}</math> || Energy released per mass of oxygen consumed; approximately 13,100 || kJ/kg
|-
| <math>\dot m_{\mathrm{O_2,consumed}}</math> || Oxygen consumption rate || kg/s
|}

For a 1 MW full-scale source, this simplified conversion gives 1,000/13,100 = 0.0763 kg/s of oxygen consumed. The calculation illustrates the principle at an item-fire scale; it is not a heat-release claim for a small cone-calorimeter specimen. The assumed conversion and the measured oxygen deficit must use compatible units.<ref name="Drysdale-1-96" /><ref name="VR-4.6">Van Rossum (2027), §4.6.</ref>

An oxygen concentration alone does not give this mass-consumption rate. The instrument also needs the exhaust flow and the incoming-air reference, with corrections appropriate to the apparatus and gas measurements. Incomplete combustion, including carbon-monoxide production, can require corrections to the simple heat-per-oxygen relation.<ref name="Drysdale-1-96" /><ref name="Janssens-3-38" />

Janssens describes the cone calorimeter with a 0.1 m × 0.1 m specimen under controlled irradiation. The measured heat release per specimen area can support comparisons between materials at that exposure. It does not by itself determine the burning area, ventilation or thermal feedback of a complete room fire.<ref name="Janssens-cone" /><ref name="Babrauskas-3-3" />

== Single Burning Item and room tests ==

The [[Single Burning Item test]] (SBI) uses two wall panels in a corner configuration without a ceiling and is a regulatory heat-release test for building products. It evaluates product response under that specified exposure. Results should not be interpreted as direct measurements of every wall or room installation.<ref name="Babrauskas-SBI">Babrauskas (2002), p. 3-32.</ref>

A [[Room corner test]] places materials in a small enclosure with a defined burner and opening, then collects combustion products in a hood and exhaust duct. It includes hot-layer and room-surface feedback that open-burning tests omit. This makes it useful when enclosure effects are expected to influence heat release.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-1" />
[[File:fse-fire-testing-v2.svg|thumb|upright=1.5|alt=Two wall panels in an open corner and a burner in a room with a hot upper layer.|SBI and room-corner tests represent different boundary conditions. Based on Babrauskas (2002), p. 3-33 and Janssens (2002), p. 3-39.]]

Room tests can differ from open calorimetry as fire grows. Babrauskas reports limited augmentation for some upholstered chairs at lower heat release rates, but much stronger effects for mattresses and liquid pools. A single room correction is therefore not valid for every product.<ref name="Babrauskas-3-2">Babrauskas (2002), p. 3-2.</ref>

Room-fire data also cannot be extrapolated directly to rooms with larger ventilation. Open-burning data may instead suit well-ventilated conditions when the fuel package is comparable. The source test and intended enclosure must be matched explicitly.<ref name="Babrauskas-3-2" />

== Large-scale and system tests ==

A [[Large-scale facade fire test]] evaluates facade systems at a scale where joints, cavities, cladding layers and external flames can interact. Such tests are relevant to system behaviour that cannot be inferred reliably from small material specimens. The actual method and installation remain necessary when applying the result.<ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref><ref name="CVM2-64" />

Fire-resistance tests expose structural and separating assemblies to a defined furnace curve. Milke explains that ASTM E119 addresses structural integrity, temperature, flame and hot-gas passage and, in some cases, hose-stream response. These criteria are distinct from reaction-to-fire measurements of a material's own combustion.<ref name="Milke-4-209" /><ref name="Milke-4-210">Milke (2002), pp. 4-209–4-210.</ref>

Large tests can still be comparative rather than literal full-scale reproductions. Furnace dimensions, loading and end restraints may differ from the built structure. Actual performance requires appropriate analytical extension and validation rather than assuming the test building is identical.<ref name="Milke-4-210" />

C/VM2 (second edition, 2025) determines fire resistance ratings from standard tests or calculation methods verified by experimental data from standard tests. Its ratings report structural adequacy, integrity and insulation in that order. This is a regulatory use of fire-test evidence within New Zealand.<ref name="CVM2-64" />

== Data quality and uncertainty ==

Measurement uncertainty includes bias and random error. Calibration with a metered high-purity gas can reduce bias in oxygen-consumption systems, while interlaboratory trials help quantify random error. The 95% confidence intervals reported for some tests should be retained when comparing results.<ref name="Babrauskas-3-33" />
[[File:fse-fire-testing-v3.svg|thumb|upright=1.5|alt=Calibration addresses bias, repeated trials show random error and a model adds extrapolation uncertainty.|Fire-test uncertainty comes from measurement and application. Based on Babrauskas (2002), pp. 3-33–3-34.]]

Apparatus features influence results. Heater spectrum and orientation, specimen mounting, exhaust flow and gas analysis can all affect the measured curve. Using different methods without checking those features can produce apparent material differences that are really method differences.<ref name="Janssens-3-56">Janssens (2002), p. 3-56.</ref><ref name="Janssens-3-39" />

Specimen selection adds uncertainty. Composite products may have varying layers, moisture and manufacturing quality, and a small specimen may not represent the whole. Full-scale tests reduce some of these issues but introduce cost, ventilation and installation variability.<ref name="Babrauskas-3-3" /><ref name="Kodur-Harmathy-1-156">Kodur and Harmathy (2002), p. 1-156.</ref>

Data should include the complete time history and its definitions. Peak heat release rate, an early average and a long-term average answer different questions, and their values need not agree. The averaging interval and ignition reference must be stated.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-56" />

== Using results in engineering ==

Results can support material comparison, regulatory classification and design-fire selection. The intended use determines which measurements and acceptance criteria matter. A test that suits one purpose may not provide the data needed for another.<ref name="CVM2-52">Ministry of Business, Innovation and Employment (2025), p. 52.</ref><ref name="Janssens-3-39" />

For reaction-to-fire assessment, heat release, ignition, spread and smoke describe how a product contributes to fire. For fire resistance, the construction's ability to continue separating or supporting loads is central. Confusing these measures can lead to incorrect claims about a material or assembly.<ref name="CVM2-64" /><ref name="Milke-4-209" />

For modelling, bench-scale data can be extrapolated only with a defensible model. Full-scale data are stronger evidence when they match the actual fuel package and enclosure, but even then installation and ventilation differences need review. Similar product names are not enough.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-39" />

For regulatory use, the applicable standard and edition must be identified. C/VM2 uses its 2025 second edition and New Zealand context, while ASTM E119 and ISO room tests have their own methods and criteria. A class or rating should not be transferred between systems without demonstrating equivalence.<ref name="CVM2-64" /><ref name="Milke-4-210" />

== Limits and common misunderstandings ==

A fire test does not prove performance in every real fire. It proves response under the reported exposure and arrangement. Extrapolation needs a model, compatible conditions and acknowledgment of uncertainty.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-39" />

A larger test is not automatically a better test. Scale can introduce important room and system feedback, but it can also make results harder to reproduce and apply elsewhere. The appropriate scale depends on the decision and the controlling mechanisms.<ref name="Babrauskas-3-2" /><ref name="Janssens-3-39" />

A standard test is not a universal measure of noncombustibility or safety. It characterises particular properties, and other hazards such as toxicity, installation and changing ventilation may remain. All relevant performance criteria should be considered.<ref name="Purser-2-96" /><ref name="CVM2-64" />

test data are not free of error merely because they follow a standard. Calibration, specimen preparation, instrument response and averaging still matter. These details belong with the data used for design or publication.<ref name="Babrauskas-3-33" /><ref name="Janssens-3-56" />

== Test selection and review ==

Test selection should begin with the decision and its controlling mechanisms. Material-level ignition and heat release may be sufficient for a simple comparison, but an enclosure or assembly can introduce new feedback. The test should include those mechanisms without adding irrelevant complexity.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

A test plan should specify the specimen, exposure, instrumentation and endpoint before testing. Mounting, backing, moisture, orientation and pilot location can all change the result. Recording these choices makes the resulting data reproducible and helps prevent an incorrect comparison with another method.<ref name="Janssens-3-56" /><ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref>

The exposure should be characterised as a time history where relevant. A constant radiant panel, a furnace curve and a developing compartment fire produce different boundary conditions. Using the first two as though they were interchangeable with the third would hide important transient behaviour.<ref name="Lie-4-201">Lie (2002), pp. 4-201–4-203.</ref><ref name="VR-5.1">Van Rossum (2027), §5.1.</ref>

Instrumentation should match the quantity required. Load cells measure mass loss, gas analysers measure species, exhaust measurements support oxygen-consumption calculations, and temperature and heat-flux instruments describe exposure. No one instrument supplies all of those outputs reliably without supporting measurements.<ref name="Janssens-3-56" /><ref name="Babrauskas-3-33" />

A test series can examine sensitivity rather than produce only one result. Changing heat flux, orientation, backing or ventilation reveals whether a conclusion remains stable. Those variations also identify the conditions under which extrapolation to the intended installation becomes uncertain.<ref name="Quintiere-2-247">Quintiere (2002), p. 2-247.</ref><ref name="Babrauskas-3-3" />

Interlaboratory comparison adds another check. It can reveal apparatus, operator and analysis differences that a single-laboratory procedure would miss. Confidence intervals should be reported alongside the measured curve so that small differences between products are not overinterpreted.<ref name="Babrauskas-3-33" />

Validation should compare like with like. A bench-scale heat-release curve should not be compared directly with a room-fire curve without accounting for enclosure feedback, and a layer-average temperature should not be compared directly with a near-ceiling reading. Definitions must match before agreement can be assessed.<ref name="Babrauskas-3-1" /><ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

A final report should separate measurement, calculation and acceptance. It states what was observed, which conversions were applied and which criterion was used to judge performance. This keeps the test result traceable when it is later used for classification, modelling or a design decision.<ref name="Janssens-3-39" /><ref name="CVM2-64" />

The [[Euroclass system]] illustrates why a test must be read through its regulatory method. A result becomes a classification only after the applicable procedures and criteria are applied, and another framework can use different evidence. The underlying measurement should not be assigned a class from an unrelated system without an equivalence assessment.<ref name="Janssens-3-38" /><ref name="CVM2-52" />

Acceptance criteria should be checked against the test's actual output. A furnace endpoint may be a temperature, a heat-release threshold, a spread observation or a retained structural function. Using the wrong endpoint can make a successful measurement answer an unsuccessful design question.<ref name="CVM2-64" /><ref name="Milke-4-210" />

For product comparison, uncertainty should be included when differences are small. Calibration and specimen variation can create differences of the same order as the apparent product effect. Repeating the exposure or comparing independent laboratories can show whether the ranking persists.<ref name="Babrauskas-3-33" /><ref name="Janssens-3-56" />

For design, the complete evidence chain should be documented. It links the tested specimen and exposure to the conversion, model and acceptance criterion used in the building. Any weak link can change the conclusion even when the original measurement is sound.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

A final review should also state which hazards were outside the test. Limited smoke, toxicity, ageing, installation damage and altered ventilation may not be represented. A fire-test result should therefore be used for the properties it measures, not as a guarantee of complete fire safety.<ref name="Purser-2-96" /><ref name="Kodur-Harmathy-1-156" />

The test's role in the wider evidence chain should also be explicit. A result can support a classification, supply a model input or validate a predicted response, but those uses have different evidence requirements. A measurement that is adequate for one role may be incomplete for another.<ref name="Janssens-3-39" /><ref name="Babrauskas-3-3" />

== See also ==

* [[Froude scaling]]
* [[Heat release rate]]
* [[Combustibility]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Janssens, M. (2002). Calorimetry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Lie, T. T. (2002). Fire temperature-time relations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Milke, J. A. (2002). Analytical methods for determining fire resistance of steel members. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.). New Zealand Government.
* Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Materials & Fire Testing]]

Combustibility

2026-11-02T17:59:01Z

Thomas: Improve Combustibility: sourced explanations, calculations and internal links (Codex)

'''Combustibility''' is the ability of a material to burn under specified conditions. A combustible material can act as fuel, contributing chemical energy and combustion products to a fire. The related term noncombustibility should also be applied with its test and regulatory context rather than treated as an absolute statement about every exposure.<ref name="Kodur-Harmathy-1-157">Kodur and Harmathy (2002), p. 1-157.</ref><ref name="CVM2-52">Ministry of Business, Innovation and Employment (2025), p. 52.</ref>

Combustibility is not a complete description of fire behaviour. It does not specify ignition temperature, heat release rate, flame spread, smoke yield or toxicity. Those properties require separate measurements and scenario conditions, including orientation, thickness, backing and ventilation.<ref name="Quintiere-2-247">Quintiere (2002), p. 2-247.</ref><ref name="Mulholland-2-259">Mulholland (2002), p. 2-259.</ref>

A material can have a structural or insulating role and still become fuel when exposed to sufficient heat. Its fire performance therefore depends on both its intended function and its contribution to the fire itself.<ref name="Kodur-Harmathy-1-157" />

== Combustible materials as fuel ==

Combustible materials store chemical energy that can be released through oxidation. [[Fire load]] describes the total energy potentially available from those materials in a defined inventory. Combustibility identifies the possibility of burning, while fire load quantifies potential energy.<ref name="VR-4.4">Van Rossum (2027), §4.4.</ref><ref name="Drysdale-1-92">Drysdale (2002), p. 1-92.</ref>

The heat of combustion provides one part of this energy description. Complete oxidation values are measured under controlled conditions and do not predict actual energy release in every fire. Incomplete combustion, protected contents and moisture can reduce the effective contribution.<ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref><ref name="IFEG-2.4-2">Australian Building Codes Board et al. (2005), pp. 2.4-2–2.4-3.</ref>

Materials also differ in how readily they release that energy. Gases can mix directly with air, liquids generally evaporate, and many solids require thermal decomposition. A material can therefore be combustible without supporting immediate or sustained flaming under a particular exposure.<ref name="VR-4.1">Van Rossum (2027), §4.1.</ref><ref name="VR-3.1">Van Rossum (2027), §3.1.</ref>

Kodur and Harmathy distinguish burnable and nonburnable materials in their review, while noting that burnable structural materials can change from performing an intended role to adding to fire severity. This is why fuel contribution and structural contribution must be evaluated separately.<ref name="Kodur-Harmathy-1-157" />
[[File:fse-combustibility-v1.svg|thumb|upright=1.5|alt=One component shown as structure or insulation and as a fuel source.|A material can have both a design function and a fuel role. Based on Kodur and Harmathy (2002), p. 1-157.]]

== Ignition and flame spread ==

Combustibility becomes evident when a material ignites and sustains combustion, but the required exposure varies. Heat flux, exposure time, pilot arrangement and heat losses determine whether a critical condition is reached. No single universal ignition threshold applies to every material configuration.<ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref><ref name="IFEG-3.3-3">Australian Building Codes Board et al. (2005), p. 3.3-3.</ref>

[[Flame spread]] is movement of a flame over or adjacent to condensed fuel as new regions are heated and decomposed. A material may be combustible but resist spread because of its thermal response, char formation or heat losses. Another can ignite readily and support rapid spread under the same exposure.<ref name="Quintiere-2-246">Quintiere (2002), p. 2-246.</ref><ref name="Quintiere-2-247" />

Orientation and airflow matter. Upward spread can preheat material above the flame, whereas lateral or downward spread uses different forward heat-transfer paths. A material's combustibility should therefore be evaluated in the intended installation, not only in a convenient test orientation.<ref name="VR-4.3">Van Rossum (2027), §4.3.</ref><ref name="Quintiere-2-247" />
[[File:fse-combustibility-v2.svg|thumb|upright=1.5|alt=Heat source, target material, orientation, backing and heat losses shaping ignition and spread.|Combustibility is expressed through source, target and conditions. Based on Kanury (2002), pp. 2-230–2-232 and Quintiere (2002), p. 2-247.]]

Thermal properties also influence the response. Conductivity, density, specific heat and thermal diffusivity affect how quickly a surface and its interior heat. Composite and anisotropic materials can have different properties in different directions.<ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref><ref name="Kodur-Harmathy-1-156">Kodur and Harmathy (2002), p. 1-156.</ref>

== Reaction to fire and testing ==

[[Reaction to fire]] describes how a material or product responds to fire exposure, including ignition, heat release, spread and sometimes smoke or toxic products. Combustibility is one part of that response but does not replace the complete measurement. Test conditions and product form are essential to interpretation.<ref name="Janssens-3-38">Janssens (2002), pp. 3-38–3-39.</ref><ref name="Quintiere-2-247" />

The [[Euroclass system]] is an example of a regulatory classification framework for reaction to fire. Such a system uses defined tests and criteria, so its classifications must not be inferred from material name or generic combustibility alone. The applicable edition and jurisdiction should be stated when a class is used.<ref name="CVM2-52" /><ref name="Janssens-3-38" />

New Zealand's C/VM2 (second edition, 2025) describes Group Number 1 materials as noncombustible or limited-combustibility materials, with plasterboard and similar low-hazard materials as examples. Group Number 2 includes many fire-retardant-treated timbers, Group Number 3 ordinary timber products and Group Number 4 exposed polyurethane foams. These are classifications within that document, not universal categories.<ref name="CVM2-52" />
[[File:fse-combustibility-v3.svg|thumb|upright=1.5|alt=Four C/VM2 groups from limited combustibility to exposed polyurethane foam.|Material groups in New Zealand C/VM2 (2025). Based on Ministry of Business, Innovation and Employment (2025), p. 52.]]

C/VM2 also uses critical radiant flux for flooring performance, with higher flux corresponding to better performance in its commentary. The criterion depends on occupancy, escape function and sprinkler protection. This illustrates how combustibility-related performance is evaluated against a scenario rather than as an isolated label.<ref name="CVM2-52" />

New Zealand's C/VM2, second edition (2025), provides an example of a classification with a defined application. Its Group Numbers concern exposed interior wall and ceiling lining surfaces, and §4.7.2.2 refers determination of those numbers to the Building Product Specifications. The document's lists of material types illustrate the groups; they do not replace the specified classification process for a particular product.<ref name="CVM2-linings">Ministry of Business, Innovation and Employment (2025), §§4.7.1.5 and 4.7.2.2, pp. 50–52.</ref>

This distinction separates a broad description such as combustible timber from evidence for a particular lining system. Backing, joints, coatings and exposed surfaces can change the tested product. A classification therefore describes the tested or assessed application within its stated conditions, rather than every installation containing the same base material.<ref name="CVM2-linings" /><ref name="Beyler-char">Beyler and Hirschler (2002), p. 1-113.</ref>

== Composite products and installations ==

A [[Sandwich panel]] combines facings, a core, joints and fixings, which can respond differently during heating. One component may provide insulation while another supplies fuel. Panel performance therefore cannot be deduced from a single constituent without considering the assembled product.<ref name="Kodur-Harmathy-1-156" /><ref name="Rockett-Milke-1-29" />

Composite and porous materials can contain solid, liquid and gaseous phases. Moisture affects thermal properties and energy consumption, while pores can support oxygen transport and smouldering. The material's microstructure consequently influences its macroscopic fire response.<ref name="Kodur-Harmathy-1-156" /><ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref>

A [[Facade fire]] adds external flame exposure, cavities, cladding geometry and possible spread between floors. Combustible facade components can contribute to this pathway, but their effect depends on installation and fire source. A material classified in one test arrangement still needs evaluation in the facade system.<ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref><ref name="CVM2-52" />

Protected and encapsulated fuel also requires attention. Combustible insulation behind a facing can remain uninvolved until the facing fails or heats sufficiently. The inventory may then change abruptly, demonstrating why material presence and actual fire contribution differ.<ref name="IFEG-2.4-2" /><ref name="Beyler-Hirschler-1-110">Beyler and Hirschler (2002), p. 1-110.</ref>

== Properties that influence response ==

Conductivity affects how quickly energy moves into and through a material, while heat capacity affects storage. Density and moisture influence both. These properties can change during heating, so ambient values do not necessarily describe the material throughout a fire.<ref name="Rockett-Milke-1-29" /><ref name="Kodur-Harmathy-1-163">Kodur and Harmathy (2002), p. 1-163.</ref>

Char formation can reduce heat transfer to underlying material, but char can also oxidise and sustain smouldering. Its continuity, porosity, adherence and permeability affect whether it acts as an insulating barrier. These changing properties can alter the apparent combustibility over time.<ref name="Beyler-Hirschler-1-110" /><ref name="Beyler-Hirschler-1-114">Beyler and Hirschler (2002), p. 1-114.</ref>

Some materials melt, shrink or disintegrate before full decomposition. Thermoplastics and thermosets respond differently to heating, and those physical changes alter exposed area and heat transfer. A material that initially appears protected can therefore become exposed later.<ref name="Beyler-Hirschler-1-112">Beyler and Hirschler (2002), p. 1-112.</ref>

Combustibility also says nothing about toxicity. Two materials can both burn, yet produce very different carbon monoxide, hydrogen cyanide, soot and irritant yields. Fire safety assessment must include those product yields as well as energy and spread.<ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref><ref name="Gottuk-Lattimer-2-54">Gottuk and Lattimer (2002), p. 2-54.</ref>

=== Softening, decomposition and residue ===

Beyler and Hirschler distinguish thermal decomposition from a loss of physical performance. Decomposition changes chemical structure and can release volatile fuel, while degradation includes changes in useful properties. A material can therefore lose its original shape or strength before sustained flaming is observed.<ref name="Beyler-Hirschler-1-110" />

Thermoplastics soften and can melt as they are heated. Cross-linked thermosetting materials do not follow the same melting behaviour, although they can decompose and release combustible products. This difference helps explain why specimens with similar chemical energy can expose different burning surfaces during a test.<ref name="Beyler-Hirschler-1-112" />

Char formation changes the remaining fuel rather than proving that combustion has ended. A coherent residue can limit heat transfer and the escape of volatiles, while cracks or poor adhesion can reduce that protection. Carbonaceous char can itself oxidise after the main period of volatile release.<ref name="Beyler-char" />

Consequently, the initial specimen and the material actually burning may have different density, surface geometry and permeability. Material identity alone cannot capture these changes. Fire testing follows the response of a specified specimen and exposure, including the residue or melt that forms during heating.<ref name="Beyler-Hirschler-1-110" /><ref name="Beyler-char" />

== Use and limitations ==

Combustibility is useful for screening fuel inventory and selecting scenarios. It tells the analyst to consider a material as potential fuel and to investigate its ignition and contribution. It does not remove the need for subsequent measurements and modelling.<ref name="VR-4.4" /><ref name="IFEG-2.4-4">Australian Building Codes Board et al. (2005), p. 2.4-4.</ref>

A noncombustible label should be tied to the test or regulation that assigns it. It should not be interpreted as proof that a material cannot melt, decompose, lose strength or transfer heat. Noncombustibility and fire resistance are different properties.<ref name="Kodur-Harmathy-1-155">Kodur and Harmathy (2002), p. 1-155.</ref><ref name="CVM2-64">Ministry of Business, Innovation and Employment (2025), p. 64.</ref>

Material comparisons should use consistent specimens and exposures. Thickness, backing, moisture and test scale can change the result, and full-scale installation can add further feedback. A generic combustibility label alone is not enough to rank products safely.<ref name="Quintiere-2-247" /><ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

combustibility does not describe how much harm a fire will cause. Harm depends on heat release rate, spread, smoke, toxicity, enclosure and occupants. The material is one part of that larger scenario.<ref name="Purser-2-85" /><ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref>

== Material evidence and comparison ==

A useful comparison starts with the same exposure and product form. Heat flux, specimen orientation, backing, thickness and ignition method should be consistent, otherwise a measured difference cannot be assigned confidently to the material. Composite products also need their layers and mounting identified.<ref name="Kanury-2-231" /><ref name="Janssens-3-39">Janssens (2002), p. 3-39.</ref>

Heat release and mass loss should be evaluated together. A material can have high energy content but low combustion efficiency, while another can release energy rapidly despite a smaller inventory. Effective heat of combustion and fuel-consumption history therefore provide more insight than combustibility alone.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="Drysdale-1-95" />

Soot and toxic yields need the same conditional treatment. Material chemistry and oxygen supply can change the quantities and the types of products, and those yields can vary during the test. Early well-ventilated results should not be used to represent a developed fuel-rich fire without checking.<ref name="Purser-2-96">Purser (2002), p. 2-96.</ref><ref name="Gottuk-Lattimer-2-55">Gottuk and Lattimer (2002), p. 2-55.</ref>

Physical integrity can be as important as combustion. A material may melt, shrink, delaminate, spall or lose strength before it contributes substantial flame. Those changes can expose new fuel or allow heat and smoke to bypass the original barrier. Reaction to fire and structural performance therefore have to be assessed together.<ref name="Beyler-Hirschler-1-112" /><ref name="Kodur-Harmathy-1-163" />

The scale of the test changes interpretation. Bench-scale specimens isolate material response, while room and system tests add hot-layer radiation, ventilation and assembly effects. Selecting evidence that matches the intended application is more defensible than choosing the largest or most convenient test.<ref name="Babrauskas-3-3" /><ref name="Janssens-3-39" />

== Scenario assessment ==

For an ignition assessment, the source and target must be described. A small pilot can ignite a suitable gas mixture, but a solid target needs enough heat to produce volatiles and maintain reaction. Combustibility does not remove the need to evaluate that source-target interaction.<ref name="Kanury-2-230">Kanury (2002), p. 2-230.</ref><ref name="IFEG-2.4-4" />

For a spread assessment, the relevant paths include direct flame contact, radiation, convection and conduction. Material boundaries and openings can change those paths during the fire. A product that resists early ignition can still become involved when the surrounding exposure grows.<ref name="IFEG-1.6-7" /><ref name="VR-5.1">Van Rossum (2027), §5.1.</ref>

For a smoke assessment, total mass burned and product yields must both be estimated. A lower heat release rate can reduce total production, but a higher yield per kilogram can offset part of that reduction. Receiver concentration and exposure duration should be calculated from the resulting atmosphere.<ref name="VR-6.2">Van Rossum (2027), §6.2.</ref><ref name="Purser-2-88">Purser (2002), p. 2-88.</ref>

For structural assessment, temperature and integrity must be linked to the material's function. A combustible member can lose section and strength, while a noncombustible member can transmit heat or deform. The required criterion determines whether the material's behaviour is acceptable.<ref name="CVM2-64" /><ref name="Kodur-Harmathy-1-155" />

For facades and cavities, installation should be treated as part of the fuel geometry. Joints, air gaps and coverings can alter oxygen access, heat transfer and the route to other floors. This makes system testing and analysis necessary even when the individual material properties are known.<ref name="IFEG-1.6-7" /><ref name="CVM2-52" />

For regulated performance, the jurisdiction and edition must be explicit. C/VM2's 2025 groups and critical-radiant-flux criteria belong to New Zealand, while other frameworks use different tests and classifications. A material should not be assigned a class from one system using evidence from another without an equivalence assessment.<ref name="CVM2-52" /><ref name="Janssens-3-38" />

Where uncertainty remains, alternatives should be compared rather than hidden. Exposure, backing, moisture and installation can be varied to see whether the material's ranking or the safety conclusion changes. This shows whether a combustibility claim is broadly applicable or limited to one test configuration.<ref name="VR-1.7">Van Rossum (2027), §1.7.</ref><ref name="Quintiere-2-247" />

A final comparison should distinguish necessary from sufficient evidence. A combustible label identifies the need for analysis, but it does not prove ignition or sustained fire. Demonstrating those outcomes requires suitable exposure, fuel production, oxygen and heat feedback.<ref name="Kanury-2-230" /><ref name="VR-4.2">Van Rossum (2027), §4.2.</ref>

Material selection should likewise be based on the complete performance profile. Heat release, spread, smoke, toxicity, integrity and structural response can each favour a different product. A single combustibility statement cannot resolve those trade-offs or establish which consequence should dominate.<ref name="Purser-2-85" /><ref name="CVM2-64" />

For product development, alternative formulations and installations can be compared using the same scenario. This shows whether a change improves the relevant outcome without introducing a new exposure path. Full product evidence is especially important where a facing or treatment protects combustible material.<ref name="Janssens-3-39" /><ref name="Beyler-Hirschler-1-110" />

A clear report therefore identifies the material, its intended function, the exposure and the criteria used. It also records which fire and structural consequences were assessed and which remain open. This makes combustibility a useful starting point for analysis without presenting it as a complete safety conclusion.<ref name="Janssens-3-39" /><ref name="CVM2-64" />

For final acceptance, the evidence should be weighed against the actual fire scenario rather than a generic material description. A product that performs as intended in one exposure can be unsuitable in another, and the governing criterion should determine which data are needed. This keeps combustibility tied to a measurable fire process.<ref name="Quintiere-2-247" /><ref name="Kanury-2-231" />

== See also ==

* [[Flame retardant]]
* [[Photovoltaic system fire]]
* [[Wildland-urban interface]]
* [[Large-scale facade fire test]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Beyler, C. L., & Hirschler, M. M. (2002). Thermal decomposition of polymers. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Janssens, M. (2002). Calorimetry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kodur, V. K. R., & Harmathy, T. Z. (2002). Properties of building materials. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.). New Zealand Government.
* Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Materials & Fire Testing]]

Soot

2026-11-02T17:58:55Z

Thomas: Improve Soot: sourced explanations, calculations and internal links (Codex)

'''Soot''' is the carbonaceous particulate material produced mainly by incomplete combustion. It is a component of smoke rather than the whole smoke mixture, and contributes to dark colour, optical extinction and flame radiation. Its amount and properties depend on fuel chemistry, combustion mode, oxygen supply and transport.<ref name="VR-6.2">Van Rossum (2027), §6.2.</ref><ref name="Mulholland-2-258">Mulholland (2002), p. 2-258.</ref>

Soot forms through growth processes in fuel-rich combustion regions and can be consumed later through oxidation. Flaming smoke often contains elemental graphitic carbon, while pyrolysis and smouldering also produce droplets with different properties. A complete description therefore distinguishes soot particles from other aerosol and gas components.<ref name="Mulholland-2-258" /><ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref>

Soot matters because it can obscure escape routes, expose people and structures to radiation and provide a measurable indicator of incomplete combustion. Its effects depend on production per unit fuel, total fuel consumed and subsequent transport and deposition.<ref name="VR-6.2" /><ref name="Mulholland-2-259">Mulholland (2002), p. 2-259.</ref>

== Formation in flames ==

[[Incomplete combustion]] leaves carbon in partially oxidised or elemental forms instead of converting it all to carbon dioxide. Soot grows in fuel-rich flame regions and can later burn out where oxygen and temperature are suitable. Emission reflects the balance between these formation and consumption processes.<ref name="Mulholland-2-258" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

Fuel chemistry affects this balance. Mulholland notes that aromatic polymers such as polystyrene produce more smoke than hydrocarbons with single carbon-carbon bonds in the cited comparison. Material structure therefore influences soot production alongside oxygen and heat.<ref name="Mulholland-2-258" />

The fuel-rich side of a hydrocarbon-air diffusion flame favours thermal decomposition and carbon formation. This region is associated with yellow luminosity from hot carbon particles. Other flame regions have different oxygen availability and can support further oxidation.<ref name="Simmons-1-151">Simmons (2002), pp. 1-151–1-152.</ref><ref name="VR-4.3">Van Rossum (2027), §4.3.</ref>
[[File:fse-soot-v1.svg|thumb|upright=1.5|alt=Soot forms in the fuel-rich flame zone and oxidises nearer the air side.|Soot forms and is consumed in different flame regions. Based on Mulholland (2002), p. 2-258 and Simmons (2002), pp. 1-151–1-152.]]

Soot production is not limited to large fires. Small diffusion flames can also emit particles, and weakly visible flames can indicate low rather than absent soot production. Appearance alone cannot quantify the source.<ref name="VR-4.3" /><ref name="Mulholland-2-258" />

== Soot yield ==

[[Soot yield]] is the mass of soot produced per unit mass of fuel burned, commonly expressed as kilograms of soot per kilogram of fuel or as a percentage. It is a source property under specified combustion conditions, not the concentration at a remote receiver. Concentration also depends on smoke volume and transport.<ref name="VR-6.2" /><ref name="Mulholland-2-259" />

Van Rossum gives pre-flashover values of 1.5% for wood, 23% for polyurethane, 14% for PVC, 16% for polystyrene and 19.5% for expanded polystyrene. These values apply to oxygen excess in the cited source. They illustrate strong material dependence but should not be transferred unchanged to ventilation-limited fires.<ref name="VR-6.2" />
[[File:fse-soot-v2.svg|thumb|upright=1.5|alt=Soot yields: wood 1.5, polyurethane 23, PVC 14, polystyrene 16 and expanded polystyrene 19.5 percent.|Pre-flashover soot yields for selected materials. Based on Van Rossum (2027), §6.2.]]

Mulholland reports smoke conversion factors from 0.001 to 0.17 for flaming combustion and from 0.01 to 0.17 for pyrolysis and smouldering across the reviewed experiments. Most were measured on small samples under free-burning ambient conditions, and reduced ventilation can strongly affect them. The term smoke conversion factor includes a broader aerosol definition than soot alone.<ref name="Mulholland-2-259" />

A higher yield does not necessarily mean more total soot. Suppressed or smouldering fires can have higher yield per kilogram while consuming less fuel and producing less power. Total source mass therefore requires both yield and fuel-consumption history.<ref name="VR-6.2" />

=== From fuel consumption to soot mass ===

Soot yield relates emitted soot mass to consumed fuel mass under specified combustion conditions. When released energy and an applicable effective heat of combustion are known, they also give the consumed fuel mass. A homogeneous-layer calculation then divides soot mass by layer volume to obtain concentration.<ref name="VR-6.3">Van Rossum (2027), §6.3.</ref><ref name="VR-6.5">Van Rossum (2027), §6.5.</ref>
<math display="block">m_s=y_s m_f=y_s\frac{E}{\Delta H_{c,\mathrm{eff}}},\qquad C_s=\frac{m_s}{V}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>m_s</math> || Soot mass entering the modelled layer || kg
|-
| <math>y_s</math> || Soot mass per mass of fuel consumed || kg/kg
|-
| <math>m_f</math> || Fuel mass consumed || kg
|-
| <math>E</math> || Energy released || MJ
|-
| <math>\Delta H_{c,\mathrm{eff}}</math> || Effective heat of combustion || MJ/kg
|-
| <math>C_s</math> || Soot mass concentration || kg/m³
|-
| <math>V</math> || Layer volume || m³
|}

Van Rossum's shop example releases 120 MJ, uses 20 MJ/kg and distributes the products through 450 m³. Substituting the wood soot yield of 0.015 kg/kg consumes 6.0 kg of fuel and gives 0.090 kg of soot. The resulting soot concentration is 0.000200 kg/m³.<ref name="VR-6.5" /><ref name="VR-yield-secondary">Van Rossum (2027), §6.2, summarising the compilation in Robbins and Wade (2008).</ref>

Using the book's decimal optical-density coefficient of 3,300 m²/kg gives 0.66 m⁻¹. Its non-luminous visibility approximation, 1 divided by that optical density, gives about 1.5 m. This is a source-based sensitivity example: changing the assumed yield changes visibility while the energy release and layer volume remain fixed.<ref name="VR-6.4">Van Rossum (2027), §6.4.</ref><ref name="VR-6.5" />

The calculation assumes uniform mixing and no removal of soot from the selected layer. Deposition would remove airborne particles; coagulation alone changes their number and size without removing their combined mass. Optical properties can nevertheless change with particle size, shape and composition, so one mass coefficient is an approximation.<ref name="Mulholland-2-261">Mulholland (2002), pp. 2-261–2-262.</ref><ref name="Mulholland-2-263">Mulholland (2002), p. 2-263.</ref>

The wood value belongs to the pre-flashover conditions summarised by Van Rossum. His table compiles earlier material data through Robbins and Wade, so it does not establish a constant yield for every timber product or ventilation state. A different combustion regime requires evidence appropriate to that regime.<ref name="VR-yield-secondary" />

== Optical density and visibility ==

[[Optical density]] describes light attenuation using a decimal logarithm. Van Rossum uses an average mass coefficient of 3,300 m²/kg with this decimal convention. The natural-logarithm extinction coefficient is larger by a factor of ln(10), so the same numerical coefficient cannot be used for both conventions.<ref name="VR-6.4" /><ref name="Mulholland-2-263" />

Particle mass concentration is calculated from soot mass and the volume over which it is distributed. Uniform mixing is a modelling assumption, and real rooms can have strong spatial variation. Optical density along an actual sightline may therefore require integration rather than one room-average value.<ref name="VR-6.3" /><ref name="VR-6.5" />

[[Visibility in smoke]] also depends on object contrast, illumination and the observer. Soot particles block and scatter light, reducing the contrast needed to recognise an object or sign. More lighting can increase scattering and fail to improve recognition.<ref name="Jin-2-43">Jin (2002), p. 2-43.</ref><ref name="VR-6.5" />

Van Rossum's worked shop-fire example uses 1 MW for 120 seconds, effective heat of combustion of 20 MJ/kg, soot yield of 0.1 kg/kg and a 450 m³ layer. It produces 0.6 kg of soot and an optical density of 4.4 per metre. The corresponding rough visibility estimates are 0.23 m for a non-luminous object and 0.57 m for a luminous one, showing how quickly a layer can become effectively opaque.<ref name="VR-6.5" />
[[File:fse-soot-v3.svg|thumb|upright=1.5|alt=Generic yield gives OD 4.4 and wood gives OD 0.66 per metre with different visibility estimates.|Soot yield strongly affects optical density and visibility. Based on Van Rossum (2027), §6.5.]]

The same example with wood soot yield of 0.015 kg/kg gives an optical density of 0.66 per metre and visibility of about 1.5 m. These calculations depend on the stated yield, volume and uniform-smoke assumptions. They should not be treated as expected values for another room.<ref name="VR-6.5" />

== Flame radiation ==

[[Flame radiation]] includes emission from hot soot particles, which radiate as approximate blackbody sources. This contributes to yellow and orange flame appearance and to heat transfer towards fuel and surrounding objects. Low soot production can make a flame difficult to see without eliminating its thermal hazard.<ref name="VR-4.3" /><ref name="Tien-1-73">Tien, Lee, and Stretton (2002), p. 1-73.</ref>

Soot radiation often contributes more than gaseous radiation in the situations discussed by Tien and colleagues. Water vapour, carbon dioxide and hydrocarbon gases also participate, so total emission depends on the complete medium. Soot is important but not the only radiating component.<ref name="Tien-1-73" />

Radiative feedback supports pyrolysis and fire spread by heating unburnt fuel. Hot soot in flames and upper layers can therefore influence objects beyond direct flame contact. The receiver's geometry and exposure time still determine its response.<ref name="VR-4.3" /><ref name="Tien-1-75">Tien, Lee, and Stretton (2002), p. 1-75.</ref>

Reduced-scale experiments can change the radiative share because flame size affects radiation relative to convection. Soot measurements and radiation data should consequently retain scale and configuration. A small test does not automatically represent a full-scale soot-radiation environment.<ref name="Tien-1-73" />

== Particle size and transport ==

Particle size distribution influences optical properties, deposition and detection. Mulholland treats size distribution and smoke concentration as the principal determinants of many smoke properties. A distribution often spans several orders of magnitude and is conveniently shown on a logarithmic scale.<ref name="Mulholland-2-259" /><ref name="Mulholland-2-260">Mulholland (2002), p. 2-260.</ref>

The geometric mean diameter and geometric standard deviation summarise many approximately log-normal distributions. These describe a distribution's central size and width rather than one identical particle size for the whole smoke. A monodisperse distribution has a geometric standard deviation of one.<ref name="Mulholland-2-260" />

During transport, particles can coagulate, partially evaporate or deposit through diffusion and sedimentation. Additional droplets can form through condensation. These processes change concentration and size distribution before smoke reaches a remote location.<ref name="Mulholland-2-259" />

Van Rossum notes that soot can settle while gases spread farther through a building. Visibility can then improve even though carbon monoxide remains high. Deposition reduces local particle concentration but does not demonstrate that the complete smoke hazard has disappeared.<ref name="VR-6.1">Van Rossum (2027), §6.1.</ref>

== Soot and other smoke components ==

[[Smoke]] includes soot, other particles, droplets, gases and entrained air. Soot contributes to colour and extinction but does not determine the entire toxic or thermal hazard. Carbon monoxide, hydrogen cyanide and other gases require separate assessment.<ref name="VR-6.1" /><ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref>

Smouldering aerosol can have much larger particles than sooty flaming smoke. In one cellulosic-insulation study described by Ohlemiller, the mass mean particle size was 2 to 3 micrometres, compared with much smaller cigarette and flaming-combustion particles. This affected detector sensitivity and transport through the fuel bed.<ref name="Ohlemiller-2-203">Ohlemiller (2002), p. 2-203.</ref>

Soot is also not identical to ash. It is emitted particulate material associated with combustion, whereas residue can include char and inorganic material left at the fuel. Char can insulate underlying material or oxidise later, affecting further soot and gas production.<ref name="Beyler-Hirschler-1-110">Beyler and Hirschler (2002), p. 1-110.</ref><ref name="Ohlemiller-2-200" />

== Measurement and modelling ==

Soot-yield measurement must match the combustion mode, oxygen supply and material form. Small free-burning tests provide useful data, but compartment ventilation and scale can change the result. A single material value should not be used without these conditions.<ref name="Mulholland-2-259" /><ref name="VR-6.2" />

Mass released can be estimated from energy released and effective heat of combustion, then multiplied by soot yield. This calculation requires a consistent energy basis and a defensible effective heat of combustion. It does not directly measure concentration until the smoke volume is specified.<ref name="VR-6.3" />

Particle-size instruments respond to different physical properties, including electrical mobility and optical behaviour. Their measurement basis can affect the resulting distribution, so a comparison should use compatible methods or an appropriate conversion. The full distribution is often more informative than one average diameter.<ref name="Mulholland-2-260" />

Smoke models then connect source yield with plume entrainment, layer volume and transport. Uniform-layer assumptions can obscure local gradients, while deposition and condensation can change the aerosol along its path. Optical and toxic results should be evaluated at the receiver.<ref name="VR-9.2">Van Rossum (2027), §9.2.</ref><ref name="Mulholland-2-259" />

== Limits and common misunderstandings ==

Soot is not all smoke. Droplets and gases can remain after soot concentration falls, and toxic gases can persist when visibility improves. Assessing only dark particles would miss these components.<ref name="VR-6.1" /><ref name="Purser-2-85" />

A high soot yield does not automatically produce a larger fire or higher total soot mass. Fuel consumption and heat release rate determine how much material is actually burned. Yield and mass must be evaluated together.<ref name="VR-6.2" />

Soot is not only a visibility problem. It contributes to flame radiation and heat transfer, and its particles can influence detector response and deposition. These effects require optical, thermal and transport analysis rather than colour alone.<ref name="Tien-1-73" /><ref name="Ohlemiller-2-203" />

a generic mass-extinction coefficient is not exact for every aerosol. Particle size, composition and measurement method affect the appropriate value. Using it without its source and assumptions can create false precision in visibility estimates.<ref name="VR-6.4" /><ref name="Mulholland-2-260" />

Source apportionment requires the same combustion-stage detail as yield measurement. Early well-ventilated burning, developed fuel-rich burning and smouldering can produce different particles and yields. Assigning one yield to an entire fire would hide those changes and could distort both optical and radiative calculations.<ref name="Mulholland-2-259" /><ref name="Purser-2-97">Purser (2002), pp. 2-96–2-97.</ref>

Soot mass should also be balanced against char and unburnt carbon remaining at the source. Not all fuel carbon becomes airborne soot, and residual char can oxidise later to carbon monoxide and carbon dioxide. This makes the emitted particle source only one part of the complete carbon pathway.<ref name="Ohlemiller-2-200" /><ref name="Drysdale-1-95" />

Measurement of emitted mass does not by itself establish human or structural exposure. The particles must be transported to a receiver, where concentration, size and incident radiation determine the effect. Deposition and coagulation can change all three along the path.<ref name="Mulholland-2-259" /><ref name="Tien-1-75" />

For detector assessment, particle size and concentration must match the detection principle. Ohlemiller's cellulosic-smoulder example had much larger particles than the flaming comparison and reduced ionisation-detector sensitivity. A detector response based only on a sooty flaming source cannot be applied to that different aerosol without evidence.<ref name="Ohlemiller-2-203" />

For radiation assessment, source temperature and emissivity should accompany soot concentration. Particles contribute strongly to emission in many fires, but gases and heated boundaries also participate. Adding these contributions requires consistent geometry and wavelength treatment rather than a universal soot-radiation fraction.<ref name="Tien-1-73" /><ref name="VR-5.4">Van Rossum (2027), §5.4.</ref>

A reproducible calculation should show the fuel-consumption estimate, soot yield, layer volume, extinction coefficient and visibility rule. It should also state whether deposition and non-uniform distribution were neglected. These details reveal which assumptions most strongly affect the predicted visibility.<ref name="VR-6.3" /><ref name="VR-6.5" />

Where those assumptions are uncertain, alternative yields and volumes can be compared. The shop example demonstrates how changing soot yield alone changes optical density and visibility by an order of magnitude. Sensitivity analysis is therefore more useful than presenting the rough visibility rules as exact distances.<ref name="VR-6.5" /><ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

Soot's changing role through the fire should also be recognised. Particles can form in one region, oxidise in another and accumulate in a layer or on a surface. Their final location affects whether they contribute to flame radiation, remote obscuration or deposited evidence rather than simply to the initial emission estimate.<ref name="Mulholland-2-259" /><ref name="Simmons-1-151" />

A final check is whether the evidence supports the chosen soot-specific conclusion. Source-yield data may not establish remote visibility, and a dark plume may not establish the local radiant flux. Linking each conclusion to the appropriate measurement and location prevents soot from becoming an imprecise proxy for the entire fire.<ref name="VR-6.5" /><ref name="Tien-1-75" />

== See also ==

* [[Flame]]
* [[Diffusion flame]]
* [[Emissivity]]
* [[Plastics in fire]]

== Notes ==

<references />

== References ==

* Beyler, C. L., & Hirschler, M. M. (2002). Thermal decomposition of polymers. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Jin, T. (2002). Visibility and human behavior in fire smoke. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Simmons, R. F. (2002). Premixed burning. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Tien, C. L., Lee, K. Y., & Stretton, A. J. (2002). Radiation heat transfer. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Smoke, Toxicity & Tenability]]

Smoke inhalation

2026-11-02T17:58:49Z

Thomas: Improve Smoke inhalation: sourced explanations, calculations and internal links (Codex)

'''Smoke inhalation''' is the intake of combustion products into the respiratory system. It can cause respiratory pain and injury, impaired vision, confusion, loss of consciousness and death. The outcome depends on gas and particle composition, concentration, exposure duration, breathing response and the exposed person's ability to escape.<ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref><ref name="VR-6.1">Van Rossum (2027), §6.1.</ref>

Inhalation is not only a problem in the room of origin. Smoke can travel through openings and shafts, exposing occupants elsewhere while the fire itself remains out of sight. Conditions in the source compartment and transport through the building both determine the received dose.<ref name="Gottuk-Lattimer-2-54">Gottuk and Lattimer (2002), p. 2-54.</ref><ref name="IFEG-2.5-6">Australian Building Codes Board et al. (2005), p. 2.5-6.</ref>

The main purpose of assessment is often to predict incapacitation as well as death. Incapacitation can prevent escape and thereby lead to a later lethal exposure. Detection, pre-movement behaviour, visibility and physical response all interact with the inhaled atmosphere.<ref name="Purser-2-85" /><ref name="Purser-2-86">Purser (2002), p. 2-86.</ref>

== Smoke components and exposure ==

[[Smoke]] contains particles, droplets, gases and entrained air. Its composition varies with fuel, combustion mode and oxygen supply. Inhalation therefore exposes a person to several hazards at once rather than to one uniform substance.<ref name="Mulholland-2-258">Mulholland (2002), p. 2-258.</ref><ref name="VR-6.1" />

[[Carbon monoxide]] is often the principal asphyxiant. It reduces oxygen carriage and can cause confusion and unconsciousness, with a dose depending on concentration, time and breathing rate. Well-ventilated and vitiated fires can produce very different yields.<ref name="Gottuk-Lattimer-2-54" /><ref name="Purser-2-97">Purser (2002), pp. 2-96–2-97.</ref>

[[Hydrogen cyanide]] is another asphyxiant and is particularly relevant to nitrogen-containing materials and some smouldering polyurethane foams. It can incapacitate rapidly at high concentration and has a different concentration-time relationship from carbon monoxide. A model limited to carbon monoxide can miss this pathway.<ref name="Purser-2-89">Purser (2002), p. 2-89.</ref><ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>

Carbon dioxide stimulates ventilation and is itself an asphyxiant at elevated concentration. Low oxygen adds hypoxia, while irritant products can cause eye and airway pain. These interactions can increase uptake and reduce the time available for escape.<ref name="Purser-2-108">Purser (2002), pp. 2-108–2-109.</ref><ref name="Purser-2-109">Purser (2002), p. 2-109.</ref>

Particles and droplets contribute to optical obscuration and can carry or consist of irritant material. Their size distribution affects where and how they travel and deposit. Some particles settle while toxic gases continue to spread, so clearer air is not necessarily safe to breathe.<ref name="Mulholland-2-259">Mulholland (2002), p. 2-259.</ref><ref name="VR-6.1" />

== Physiological effects ==

Purser groups incapacitating effects into impaired vision, respiratory tract pain and breathing difficulty, asphyxia, and pain or burns from heat. Impaired vision can result from optical opacity and from irritant effects on the eyes. These effects can directly obstruct orientation and movement.<ref name="Purser-2-85" />
[[File:fse-smoke-inhalation-v2.svg|thumb|upright=1.5|alt=Person with callouts for eye irritation, airway injury, asphyxia and heat effects.|Smoke inhalation can impair escape in several ways. Based on Purser (2002), pp. 2-85–2-86.]]

Respiratory tract effects include pain, inflammation, bronchoconstriction and laryngeal spasm, with collapse possible quickly in severe cases. Lung inflammation can also appear hours later and produce continuing respiratory distress. Removal from smoke therefore does not guarantee that all effects have ended.<ref name="Purser-2-85" /><ref name="Purser-2-86" />

Asphyxia results from toxic gases that reduce oxygen availability, transport or use. Confusion and loss of consciousness can follow, preventing purposeful escape. Carbon monoxide, hydrogen cyanide, carbon dioxide and low oxygen act through different but interacting mechanisms.<ref name="Purser-2-86" /><ref name="Purser-2-109-interactions">Purser (2002), pp. 2-109–2-110.</ref>

Heat adds pain, burns and hyperthermia, which can further prevent movement. Hot inhaled products can injure the respiratory tract as well as heat exposed skin. The complete exposure should therefore include thermal conditions alongside inhaled chemistry.<ref name="Purser-2-85" /><ref name="Purser-2-86" />

The exposed person's location changes both the dose and the available response. Someone below a stable layer can initially inhale little smoke and later encounter a descending layer, while someone travelling through a corridor can encounter several different atmospheres. A model should follow that movement rather than assigning one room-average exposure for the whole escape.<ref name="IFEG-2.5-6" /><ref name="Purser-2-85" />

Measurement intervals should be short enough to capture severe changes. A brief high-concentration pulse can dominate a dose even when the longer-term average appears moderate. Time-averaging must therefore be justified against the endpoint and the person's exposure duration.<ref name="Purser-2-88">Purser (2002), p. 2-88.</ref><ref name="Purser-2-89" />

Reports should also distinguish pain and irritation from asphyxiation. Irritants can prevent effective movement before the accumulated asphyxiant dose reaches its reference endpoint, creating additional time in the hazardous atmosphere. Ignoring that feedback can underestimate the eventual dose and the chance of collapse.<ref name="Purser-2-85" /><ref name="Purser-2-86" />

For evacuation analysis, the exposure history should be compared with detection, pre-movement and travel times. A survivable total dose is not enough if confusion or loss of consciousness occurs before the exit is reached. The relevant endpoint is the person's condition at each stage of escape.<ref name="Purser-2-85" /><ref name="Purser-2-86" />

Fire-statistics categories should be interpreted with their definitions. Room of origin, remote location, injury and death can be classified differently between datasets, and building practices vary. These sources can guide which pathways deserve attention but should not be converted directly into universal probabilities.<ref name="Purser-2-84">Purser (2002), p. 2-84.</ref><ref name="Gottuk-Lattimer-2-54" />

A final evidence review should identify what remains unknown about the atmosphere and the person. Missing yield data, uncertain transport and assumed breathing rate can each change the predicted dose. Stating those limitations is preferable to assigning a precise incapacitation time that the evidence cannot support.<ref name="Purser-2-96">Purser (2002), p. 2-96.</ref><ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

[[Fire toxicity]] includes asphyxiant and irritant effects caused by combustion products. A given endpoint occurs when the person has received an effective exposure, not simply when a particular gas appears. Concentration, duration, breathing and the selected endpoint must all be defined.<ref name="Purser-2-88" />

For short high-concentration exposures, uptake can be nearly linear with concentration multiplied by time. For longer exposures, breathing and body uptake produce a more complex relationship. Purser shows that the concentration needed for a lethal carboxyhemoglobin level at four hours differs from the proportion predicted by Haber's rule.<ref name="Purser-2-88" />

Carbon dioxide and hydrogen cyanide also depart from a simple universal Ct rule. Their concentrations strongly influence time to incapacitation, so each exposure segment needs an appropriate concentration-effect relationship. A single average concentration can hide a short severe period.<ref name="Purser-2-89" /><ref name="Purser-2-108" />

Activity and carbon dioxide-driven hyperventilation increase the volume inhaled and therefore the dose of other products. Dose assessment should state the person's activity and the atmosphere rather than treating elapsed time as the only variable.<ref name="Purser-2-109" /><ref name="Purser-2-88" />

== Fractional effective dose ==

[[Fractional effective dose|fractional effective dose]] (FED) divides the dose received during each time interval by the dose predicted to cause a specified effect, then sums the fractions. A value of one corresponds to the selected model endpoint, such as incapacitation or death. Different gases and populations require appropriate dose-effect data.<ref name="Purser-2-88" />

Purser evaluates asphyxiation, irritant effects and heat through endpoint-specific relationships. Only contributions that the selected model explicitly combines belong in the same sum. A reference fraction of one describes a model endpoint, while a design assessment may select a lower acceptance level for its intended population.<ref name="Purser-2-111">Purser (2002), pp. 2-111–2-112.</ref>

The dose calculation depends on the combustion-product yields supplied to it. A yield specifies the mass of a product emitted per mass of fuel burned, and oxygen-starved conditions can change that ratio substantially. The worked model comparison below illustrates the effect of this input on predicted exposure.<ref name="Purser-2-97" />

[[Fractional effective concentration|fractional effective concentration]] (FEC) addresses the concentration side of exposure assessment and should not be confused with accumulated dose. A high concentration for a short period and a lower concentration for a longer period can have different effects. The selected model determines how each is evaluated.<ref name="Purser-2-88" /><ref name="Purser-2-89" />

=== Dose accumulation and immediate irritation ===

For a specified cumulative endpoint, a fractional-dose model divides exposure into time intervals. Each interval contributes a fraction of the exposure associated with that endpoint under its stated conditions. Adding those fractions follows the exposure history rather than judging the atmosphere from its final concentration alone.<ref name="Purser-2-88" /><ref name="Purser-2-110">Purser (2002), p. 2-110.</ref>
<math display="block">F=\sum_j\Delta F_j,\qquad \Delta F_j=\frac{\Delta t_j}{t_I(C_j)}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>F</math> || Accumulated fraction for the selected endpoint || dimensionless
|-
| <math>\Delta F_j</math> || Contribution from interval j || dimensionless
|-
| <math>\Delta t_j</math> || Interval duration || min
|-
| <math>C_j</math> || Concentration during the interval || units required by the selected gas model
|-
| <math>t_I(C_j)</math> || Time to the endpoint at that concentration || min
|}

This notation does not supply a universal function for every gas. Carbon-monoxide uptake, hydrogen-cyanide effects and direct carbon-dioxide incapacitation have different relationships. Purser also treats carbon-dioxide-induced changes in breathing as an interaction, rather than simply another interchangeable dose term.<ref name="Purser-2-108" /><ref name="Purser-2-110" /><ref name="Purser-2-111" />

Immediate sensory irritation raises a different question: whether the current concentration impairs seeing, breathing or movement. A fractional effective concentration (FEC) assessment addresses concentration-based irritant effects, whereas cumulative dose follows exposure through time. Neither index can be substituted for the other merely because both are dimensionless.<ref name="Purser-2-88" /><ref name="Purser-2-112">Purser (2002), p. 2-112.</ref>

Purser's illustrative CFAST calculation shows the importance of the combustion input before any dose model is applied. It represents a 2.44 m × 3 m × 2.44 m compartment, medium fire growth and a floor-level opening 1 m wide and 0.3 m high. The compared carbon-monoxide yields are 0.007 kg/kg for well-ventilated burning and 0.149 kg/kg for the vitiated condition, a factor of approximately 21.<ref name="Purser-CFAST">Purser (2002), pp. 2-96–2-97.</ref>

In that theoretical case, accounting for changing yields produces a fractional effective dose near one at 200 s; fixed well-ventilated yields produce about 0.1. These are model-comparison results under the stated geometry and fire assumptions. They are not measured survival times, and the gas-yield ratio is not itself a ratio of physiological outcomes.<ref name="Purser-CFAST" />

== Transport and remote exposure ==

Gottuk and Lattimer discuss smoke-inhalation fatalities occurring away from the fire origin. The hazard therefore depends on transport through the building as well as production in the burning room. Smoke can expose people who never encounter the original flames.<ref name="Gottuk-Lattimer-2-54" />

Upper layers can spill through doorways and other openings, while shafts and ducts provide vertical paths. Pressure differences from buoyancy, wind and equipment determine the direction and rate of movement. A building-scale exposure model needs these paths rather than a source-room concentration alone.<ref name="IFEG-2.5-6" /><ref name="VR-6.6">Van Rossum (2027), §6.6.</ref>
[[File:fse-smoke-inhalation-v1.svg|thumb|upright=1.5|alt=Smoke travels from a fire room through openings and a shaft to a remote occupant.|Smoke inhalation can occur far from the fire. Based on Gottuk and Lattimer (2002), p. 2-54 and Australian Building Codes Board et al. (2005), p. 2.5-6.]]

Particle deposition and external oxidation change the mixture during transport. Visibility can improve while carbon monoxide remains high, and external burning can oxidise some toxic gases while releasing additional heat. Receiver conditions cannot be inferred from appearance alone.<ref name="VR-6.1" /><ref name="Gottuk-Lattimer-2-55">Gottuk and Lattimer (2002), p. 2-55.</ref>

[[Fire statistics]] provide evidence about where fatalities and injuries occur and which products dominate. Purser notes differences between UK and US patterns, including more deaths remote from the room of origin in the US data. Building style and cultural context can influence such comparisons, so the datasets are not universal frequencies.<ref name="Purser-2-84" />

== Escape and incapacitation ==

Purser separates the developing fire hazard from the process by which occupants escape. Survival depends on both: detection and response must occur before exposure becomes incapacitating. A person who cannot see, breathe or remain conscious has reduced ability to use an otherwise available exit.<ref name="Purser-2-85" />

The first phase involves awareness and pre-movement behaviour, before the person is strongly affected by smoke and heat. The second involves exposure that impairs escape, and the third involves death. Toxicity is therefore most important during exposure and its consequences, not only at the final endpoint.<ref name="Purser-2-85" />

Visibility can decline within tens of seconds near a fire, while irritants make the eyes and lungs painful. This can lengthen the time spent in smoke and increase inhaled dose. Good escape guidance and early detection can change that sequence by reducing exposure time.<ref name="VR-6.1" /><ref name="Jin-2-43">Jin (2002), p. 2-43.</ref>

Incapacitation is not a binary condition with one universal concentration or time. Different people have different activity, breathing and susceptibility, and mixed smoke produces several effects at once. Assessments should use a suitable population and safety margin.<ref name="Purser-2-111" /><ref name="Purser-2-88" />

== Yield data and test conditions ==

A toxic-product yield expresses how much of a species is produced per unit fuel consumed. It depends on material and combustion mode, so a value from a well-ventilated test cannot automatically represent a vitiated fire. Full-scale mass loss, ventilation and dispersal history are also needed.<ref name="Purser-2-96" />

Small-scale tests can examine specified equivalence ratios and material compositions. Full-scale tests add enclosure and flow effects, while incident data provide real-world outcomes with less control. Each evidence type addresses a different part of the problem and should be used accordingly.<ref name="Purser-2-96" /><ref name="Purser-2-84" />
[[File:fse-smoke-inhalation-v3.svg|thumb|upright=1.5|alt=Constant early yields give FED 0.1 and vitiated yields give FED 1 after 200 seconds.|Incorrect yield history can underestimate smoke-inhalation hazard. Based on Purser (2002), pp. 2-96–2-97.]]

The 2005 guidelines identify carbon monoxide as the principal toxic species for many fires but caution that atypical materials require additional species. Smouldering polyurethane foam is their example of a source that can yield significant hydrogen cyanide. Source terms should therefore be based on the actual combustible and combustion mode.<ref name="IFEG-2.4-11" />

Source yield, receiver concentration and inhaled dose must remain distinct. Entrained air can dilute concentration while increasing total mass flow, and deposition can change particles without removing gases. A complete model follows each relevant component from source to receiver.<ref name="VR-5.3">Van Rossum (2027), §5.3.</ref><ref name="Mulholland-2-259" />

== Prevention and engineering assessment ==

Limiting ignition and early fire growth reduces effluent production and can preserve more time for detection and escape. Suppression can also shorten exposure, but its effect on combustion products must be checked because incomplete combustion and yields can change. Total mass burned remains part of the assessment.<ref name="VR-6.2">Van Rossum (2027), §6.2.</ref><ref name="Purser-2-97" />

Smoke management can extract, dilute, pressurise or contain contaminated gas. The 2005 guidelines identify these as broad approaches, and their effectiveness depends on maintaining the intended flow and pressure paths. Nominal fan capacity alone does not establish safe inhaled conditions.<ref name="IFEG-2.5-7">Australian Building Codes Board et al. (2005), p. 2.5-7.</ref><ref name="VR-6.8">Van Rossum (2027), §6.8.</ref>

Alarm and escape analysis should compare the time needed for response and movement with the time to incapacitation. This includes visibility, irritants and mobility, not only a lethal FED threshold. A scenario can fail because a person becomes unable to escape before conditions become lethal.<ref name="Purser-2-85" /><ref name="Purser-2-86" />

Sensitivity analysis should vary yield, ventilation, source strength, transport and occupant activity. These uncertainties affect both concentration and dose. Presenting a range and its controlling assumptions is more defensible than an unsupported single exposure time.<ref name="Purser-2-97" /><ref name="VR-1.7" />

== Limits and common misunderstandings ==

Smoke inhalation is not only carbon monoxide poisoning. Carbon monoxide is often central, but hydrogen cyanide, carbon dioxide, low oxygen, irritants and heat can all contribute. The complete atmosphere determines the effect.<ref name="Purser-2-85" /><ref name="Purser-2-109-interactions" />

Good visibility does not prove safe air. Gases can remain after particles deposit, and diluted smoke can still contain hazardous concentrations. Optical and toxic assessments must be separate.<ref name="VR-6.1" /><ref name="Gottuk-Lattimer-2-54" />

A lethal dose is not the only useful criterion. Incapacitation can occur earlier and prevent escape, leading to a later fatal exposure. Sublethal effects therefore deserve explicit attention in design.<ref name="Purser-2-85" /><ref name="Purser-2-86" />

there is no universal lethal smoke concentration for every person and fire. Fuel, combustion conditions, transport, breathing and individual susceptibility all matter. Numerical examples are evidence for their stated models and tests, not universal thresholds.<ref name="Purser-2-88" /><ref name="Purser-2-111" />

== See also ==

* [[Tenability criteria]]
* [[Oxygen depletion]]
* [[Haber's rule]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Jin, T. (2002). Visibility and human behavior in fire smoke. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Smoke, Toxicity & Tenability]]

Smoke

2026-11-02T17:58:42Z

Thomas: Improve Smoke: sourced explanations, calculations and internal links (Codex)

'''Smoke''' is a mixture of solid particles, liquid droplets and gases produced during combustion and thermal decomposition. In fire safety, the smoke volume also includes entrained ambient air, because its temperature and total volume determine smoke movement and exposure. This broader usage differs from definitions that reserve smoke for only the condensed-phase aerosol.<ref name="VR-6.1">Van Rossum (2027), §6.1.</ref><ref name="Mulholland-2-258">Mulholland (2002), p. 2-258.</ref>

Smoke can reduce visibility, deliver toxic and irritant products, carry unburnt fuel and transfer heat. Its appearance and behaviour vary with fuel, combustion mode, oxygen supply, mixing and time. White, black, hot or weakly visible smoke therefore cannot be interpreted by colour alone.<ref name="Mulholland-2-258" /><ref name="VR-6.1" />

The mixture is produced by flaming combustion, pyrolysis and smouldering, then transported by plume and building airflows. Entrainment dilutes concentration and temperature while increasing total mass flow. A small combustion source can consequently create a large smoke volume.<ref name="Mulholland-2-258" /><ref name="VR-5.3">Van Rossum (2027), §5.3.</ref>

== Components and formation ==

Solid particles include carbonaceous soot and other condensed material, while droplets can form when low-vapour-pressure products condense. Gases include carbon monoxide, carbon dioxide, water vapour, unburnt fuel and many other decomposition products. Their proportions depend on material and combustion conditions.<ref name="Mulholland-2-258" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

Flaming combustion produces smoke through a balance between growth processes in the fuel-rich flame and burnout with oxygen. Aromatic polymers such as polystyrene tend to produce more smoke than hydrocarbons with single carbon-carbon bonds in the cited comparison. Flaming smoke often contains substantial elemental graphitic carbon.<ref name="Mulholland-2-258" />

Pyrolysis occurs when an external heat source decomposes a fuel surface. Vapour can then condense into light-coloured droplets as it rises and cools. Smouldering is self-sustaining surface oxidation rather than forced pyrolysis, and also produces droplet-rich smoke with different particle properties.<ref name="Mulholland-2-258" /><ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref>

White smoke commonly contains fine droplets and light aerosols, including condensed water or pyrolysis products, while water vapour itself is invisible. Black smoke usually contains more soot. These are tendencies in the cited descriptions, not a reliable classification of every fire.<ref name="VR-6.1" /><ref name="Mulholland-2-258" />
[[File:fse-smoke-v1.svg|thumb|upright=1.5|alt=Smoke cloud containing soot, droplets, gases and entrained air with invisible water vapour noted.|Smoke is a mixture of particles, droplets, gases and entrained air. Based on Van Rossum (2027), §6.1 and Mulholland (2002), p. 2-258.]]

== Soot and smoke yield ==

[[Soot]] is the carbonaceous particulate component associated with incomplete combustion. It contributes to dark colour, optical extinction and flame radiation. Soot is therefore one component of smoke rather than a synonym for the entire smoke mixture.<ref name="VR-6.2">Van Rossum (2027), §6.2.</ref><ref name="Mulholland-2-258" />

[[Soot yield]] expresses the mass of soot produced per mass of fuel burned. It depends on fuel and combustion conditions, with more complete combustion generally producing less soot. Plastics tend to produce more than wood in Van Rossum's examples, while ethanol produces so little that the smoke can be difficult to see.<ref name="VR-6.2" />

Van Rossum summarises pre-flashover example soot yields of 0.015 kg/kg for wood, 0.23 kg/kg for polyurethane, 0.14 kg/kg for PVC and 0.16 kg/kg for polystyrene. The values describe the cited material and combustion conditions, including available oxygen. They are secondary data from the compilation he reports, rather than universal constants for those material names.<ref name="VR-yield-secondary">Van Rossum (2027), §6.2, summarising the compilation in Robbins and Wade (2008).</ref>

Suppressed or smouldering combustion can have a higher yield per kilogram while burning less fuel overall. Total soot production therefore depends on both yield and mass consumed. Comparing materials only by percentage can misstate the actual smoke source strength.<ref name="VR-6.2" />

== Visibility and optical properties ==

[[Visibility in smoke]] is the distance over which a person can perceive an object or sign. It depends on optical density, object contrast, illumination, smoke scattering and the observer. Irritants can further reduce effective visibility by causing eye pain and impaired vision.<ref name="VR-6.5">Van Rossum (2027), §6.5.</ref><ref name="Jin-2-43">Jin (2002), p. 2-43.</ref>

Particles reduce the luminous flux reaching the eye from an object and scatter background light into that line of sight. Both effects reduce contrast. Additional lighting can therefore fail to improve visibility when scattering overwhelms the contrast needed for recognition.<ref name="Jin-2-43" /><ref name="VR-6.5" />

[[Optical density]] expresses attenuation using a base-10 logarithm. For attenuation per unit path length, it differs numerically from the extinction coefficient, which uses a natural logarithm. Both describe the same transmission when their respective exponential expressions and units are used consistently.<ref name="Mulholland-2-263">Mulholland (2002), p. 2-263.</ref>

For approximately uniform smoke, Van Rossum gives practical visibility estimates of one divided by optical density for non-luminous objects and 2.5 divided by optical density for luminous objects. He cautions that these are rough rules. Different optical densities along the actual line of sight require integration and make visibility direction-dependent.<ref name="VR-6.5" />

Jin's experiments similarly find an approximately constant product of visibility and extinction coefficient for signs over selected ranges. The product depends on sign type, reflectance and illumination, and black smoke can give somewhat better visibility than white smoke at the same extinction coefficient. This reinforces that optical density alone does not define perception.<ref name="Jin-2-43" />

=== Keeping optical conventions consistent ===

For a uniform smoke path, transmission can be written using either a natural exponential or a power of ten. Mulholland's definitions give the following conversion. The path length is part of the attenuation calculation; the coefficients themselves are expressed per metre.<ref name="Mulholland-2-263" />
<math display="block">\frac{I}{I_0}=e^{-KL}=10^{-DL},\qquad K=\ln(10)D\approx2.303D</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>I/I_0</math> || Transmitted intensity divided by incident intensity || dimensionless
|-
| <math>L</math> || Optical path length || m
|-
| <math>K</math> || Natural-logarithm extinction coefficient || m⁻¹
|-
| <math>D</math> || Decimal optical density per unit length || m⁻¹
|}

Van Rossum's simplified calculation uses D = 3,300C<sub>s</sub>, where C<sub>s</sub> is soot concentration in kg/m³ and the coefficient is in m²/kg. His approximate visibility rules are 1/D for non-luminous objects and 2.5/D for luminous objects. Substituting K for D in these rules would introduce a factor-of-2.303 error.<ref name="VR-6.4">Van Rossum (2027), §6.4.</ref><ref name="VR-6.5" /><ref name="Mulholland-2-263" />

The shop example assumes 1 MW for 120 s, a heat of combustion of 20 MJ/kg and a soot yield of 0.1 kg/kg. This releases 120 MJ, consumes 6 kg of fuel and produces 0.6 kg of soot. Uniform distribution in the stated 450 m³ layer gives C<sub>s</sub> = 0.00133 kg/m³.<ref name="VR-6.5" />

The resulting D is 4.4 m⁻¹, equivalent to K = 10.1 m⁻¹. The simple visibility estimates are approximately 0.23 m for non-luminous objects and 0.57 m for luminous objects. These very short distances follow the assumed homogeneous layer and coefficient; they are not measurements of the shop.<ref name="VR-6.5" /><ref name="Mulholland-2-263" />

Real sightlines can cross regions of different concentration, and object illumination and contrast change detection. The example therefore explains the calculation chain from burning fuel to optical attenuation. It does not replace a visibility assessment that represents the actual smoke distribution, observer and target.<ref name="VR-6.5" /><ref name="Jin-2-42">Jin (2002), pp. 2-42–2-43.</ref>

== Toxicity and inhalation ==

[[Fire toxicity]] includes asphyxiation, irritation and other physiological effects caused by combustion products. Carbon monoxide, hydrogen cyanide, low oxygen, carbon dioxide and irritant compounds can all contribute. Their yields depend on the same combustion conditions that shape the aerosol.<ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref><ref name="Gottuk-Lattimer-2-54">Gottuk and Lattimer (2002), p. 2-54.</ref>

[[Smoke inhalation]] exposes the respiratory system to this mixture. Effects can include breathing difficulty, respiratory tract pain, confusion and loss of consciousness. Heat and eye irritation can further impair escape, so toxicity influences both survival and the ability to reach safety.<ref name="Purser-2-85" /><ref name="Purser-2-86">Purser (2002), p. 2-86.</ref>

[[Carbon monoxide]] is often the principal asphyxiant, but atypical materials require other species to be assessed. Smouldering polyurethane foam, for example, can yield significant hydrogen cyanide in the 2005 guidance. A smoke assessment based only on one gas can therefore miss the dominant hazard.<ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>

Dose depends on concentration, exposure time and breathing response. Visibility can be poor while toxic dose is small during a short escape, or good while carbon monoxide remains high after particles deposit. Visibility and inhalation hazard must therefore be evaluated separately.<ref name="VR-6.1" /><ref name="Purser-2-88">Purser (2002), p. 2-88.</ref>

== Smoke movement and dilution ==

[[Smoke movement]] results from buoyancy, expansion, wind, mechanical systems and pressure differences across openings. Hot smoke rises in a plume, entrains air and can accumulate as an upper layer. Later flow through vents and shafts can expose remote spaces.<ref name="VR-6.6">Van Rossum (2027), §6.6.</ref><ref name="IFEG-2.5-6">Australian Building Codes Board et al. (2005), p. 2.5-6.</ref>

Entrainment increases the total mass and volume of smoke while reducing concentration and temperature. This dilution does not necessarily make the smoke harmless, because a greater volume can spread toxic products and energy to more locations. Source strength and receiver exposure both matter.<ref name="VR-5.3" /><ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref>
[[File:fse-smoke-v2.svg|thumb|upright=1.5|alt=Air entrained into a plume increases volume while smoke travels to another room.|Entrainment dilutes smoke while increasing its volume and spread. Based on Van Rossum (2027), §5.3 and Australian Building Codes Board et al. (2005), p. 2.5-2.]]

Particle and gas transport can differ. Soot can coagulate, evaporate or deposit on surfaces, and additional droplets can form through condensation. Gases may then remain hazardous farther from the fire even when visibility improves.<ref name="Mulholland-2-259">Mulholland (2002), p. 2-259.</ref><ref name="VR-6.1" />

Unburnt pyrolysis gases add a combustion hazard to the mixture. If they mix with oxygen under suitable thermal or ignition conditions, they can ignite as a smoke explosion or backdraft. Smoke is therefore not only a passive consequence of fire; it can become fuel for a later event.<ref name="VR-6.1" /><ref name="VR-4.10">Van Rossum (2027), §4.10.</ref>

== Smoke control ==

[[Smoke control]] uses natural ventilation, zone pressurisation, extraction, dilution and containment to limit where smoke travels and accumulates. The 2005 guidelines identify these as the principal smoke-management approaches. Each changes concentration, pressure or the available flow path.<ref name="IFEG-2.5-7">Australian Building Codes Board et al. (2005), p. 2.5-7.</ref>

Extraction removes smoke and transported energy but requires a compatible make-up-air path. Excessive extraction at one outlet can cause plug holing, drawing clean air from below and wasting capacity. Outlet arrangement and layer depth therefore affect actual performance.<ref name="VR-6.8">Van Rossum (2027), §6.8.</ref>

Pressurisation aims to keep selected spaces clear by maintaining a pressure difference, while containment limits the region available to smoke. Dilution reduces concentration but increases the total air-smoke mixture. These approaches should be evaluated against the fire and building conditions rather than treated as interchangeable.<ref name="IFEG-2.5-7" />

Smoke control can also change combustion. Additional oxygen can support more complete burning and lower carbon monoxide yield, but it can also increase heat release and spread. The effect on the whole fire must be considered, not only the concentration at one receiver.<ref name="Gottuk-Lattimer-2-55">Gottuk and Lattimer (2002), p. 2-55.</ref><ref name="VR-6.6" />

== Measurement and modelling ==

Smoke production can be described by mass produced per mass of fuel burned, but this conversion factor depends on combustion mode and test scale. Mulholland reports values from 0.001 to 0.17 for flaming combustion and from 0.01 to 0.17 for pyrolysis and smouldering in the reviewed experiments. Reduced ventilation can strongly change these results.<ref name="Mulholland-2-259" />

Particle size distribution is another basic property. It influences light extinction, deposition and detectability, and often spans several orders of magnitude. A logarithmic size axis is therefore useful when comparing distributions.<ref name="Mulholland-2-259" /><ref name="Mulholland-2-260">Mulholland (2002), p. 2-260.</ref>

Concentration, particle size, optical density and toxic-gas content answer different questions. A measurement of one cannot be substituted for another without a model. Full exposure assessment needs the mixture composition and its time history at the receiver.<ref name="Mulholland-2-258" /><ref name="Purser-2-88" />

Zone and field models estimate smoke production and movement from fire, plume and ventilation inputs. Their layer and mixing assumptions are simplifications, and local optical and toxic conditions can differ from model averages. Results should be checked against the intended receiver and time.<ref name="VR-9.2">Van Rossum (2027), §9.2.</ref><ref name="IFEG-2.5-2" />
[[File:fse-smoke-v3.svg|thumb|upright=1.5|alt=Generic yield gives OD 4.4 and visibility 0.23/0.57 m; wood gives OD 0.66 and visibility 1.5 m.|Worked smoke example with two soot-yield assumptions. Based on Van Rossum (2027), §6.5.]]

== Limits and common misunderstandings ==

Smoke is not only soot. Droplets and gases can dominate visibility, toxicity and movement, and water vapour itself is invisible. Treating every visible cloud as only carbon particles excludes much of the actual mixture.<ref name="VR-6.1" /><ref name="Mulholland-2-258" />

Colour does not establish composition or hazard. White smoke can contain irritants and toxic gases, while weakly visible smoke can still contain carbon monoxide. A clear line of sight does not prove that inhalation is safe.<ref name="VR-6.1" /><ref name="Gottuk-Lattimer-2-54" />

Dilution does not eliminate the source. It reduces concentration while increasing total smoke volume, so the same or greater mass of toxic products can reach more people. The receiver's concentration and exposure time must be assessed.<ref name="VR-5.3" /><ref name="Purser-2-88" />

smoke is not only a marker of fire. Unburnt components can ignite, and hot smoke can spread fire by radiation and convection. Its role includes fuel transport and heat transfer as well as toxicity and obscuration.<ref name="VR-6.1" /><ref name="VR-4.10" />

The smoke source should be characterised before its transport is calculated. Fuel, combustion mode, mass-loss rate, soot yield and toxic-species yield provide different parts of that description. Missing one can lead to a smoke volume estimate that cannot support optical or toxic assessment.<ref name="Mulholland-2-259" /><ref name="IFEG-2.4-11" />

Plume entrainment then links the source with layer formation. It determines how much air joins the combustion products and therefore affects both concentration and volume. Treating smoke production as fuel mass alone would omit the process that creates most of the moving mixture.<ref name="IFEG-2.5-2" /><ref name="VR-5.3" />

A receiver-focused analysis follows the actual sightline and breathing location. Optical density can vary along the route, and particle deposition can change composition before the gas arrives. These local conditions are more useful for exposure assessment than an unqualified building-average smoke density.<ref name="VR-6.5" /><ref name="Mulholland-2-259" />

For control-system review, nominal airflow should be converted into an actual smoke balance. Make-up air, leakage, plug holing and pressure differences can alter the effective path. The result should be checked at occupied locations and during the period when the system is expected to operate.<ref name="VR-6.8" /><ref name="IFEG-2.5-7" />

The possibility of delayed combustion should also remain in the scenario. Unburnt gases can accumulate under oxygen restriction and ignite after mixing later, producing a smoke explosion or backdraft. A model that treats smoke only as an inert transport tracer would miss this hazard.<ref name="VR-4.10" /><ref name="VR-4.9">Van Rossum (2027), §4.9.</ref>

A complete report therefore separates production, entrainment, transport, deposition and reception. It identifies which components are evaluated for visibility, toxicity and heat transfer, and which can burn later. This allows the same smoke mixture to be assessed for several different outcomes without losing its physical meaning.<ref name="VR-6.1" /><ref name="Purser-2-85" />

Different smoke metrics should not be collapsed into one index. Mass production describes source strength, optical density describes attenuation, toxic yield describes species production and visibility describes perception. A defensible assessment selects the metrics required for the decision rather than treating smoke as universally heavy or light.<ref name="Mulholland-2-258" /><ref name="VR-6.4" /><ref name="Purser-2-88" />

The smoke's thermal role should also remain in the energy balance. Hot gases and particles emit radiation, while convection transports energy to boundaries and adjacent rooms. These pathways can expose people and fuel even where the visible plume has become diluted.<ref name="Tien-1-73">Tien, Lee, and Stretton (2002), p. 1-73.</ref><ref name="VR-5.3" />

== See also ==

* [[Smoke stratification]]
* [[Smoke detector]]
* [[Tenability criteria]]
* [[Smoke filling]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Jin, T. (2002). Visibility and human behavior in fire smoke. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Mulholland, G. W. (2002). Smoke production and properties. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Tien, C. L., Lee, K. Y., & Stretton, A. J. (2002). Radiation heat transfer. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Smoke, Toxicity & Tenability]]

Carbon monoxide

2026-11-02T17:58:36Z

Thomas: Improve Carbon monoxide: sourced explanations, calculations and internal links (Codex)

'''Carbon monoxide''' ('''CO''') is a toxic, combustible gas produced when carbon-containing fuel is not fully oxidised to carbon dioxide. It is one of the main toxic products of fire and can be generated in especially high amounts during smouldering and ventilation-limited flaming. Its hazard depends on concentration, exposure duration, breathing response and the presence of other fire products.<ref name="Gottuk-Lattimer-2-54">Gottuk and Lattimer (2002), p. 2-54.</ref><ref name="Purser-2-88">Purser (2002), pp. 2-88–2-89.</ref>

Carbon monoxide forms part of [[Incomplete combustion]], in which fuel carbon remains partially oxidised. Well-ventilated flaming fires generally produce less carbon monoxide than fuel-rich conditions, although yields still depend on fuel and combustion arrangement. Smouldering can also generate high levels despite its lower heat release rate.<ref name="Gottuk-Lattimer-2-54" /><ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref>

Carbon monoxide can expose people near the fire and after transport to other spaces. Gottuk and Lattimer discuss fatalities from smoke inhalation away from the fire origin, linking the hazard to building-wide transport. Combustion conditions in the source compartment influence the gases entering those flow paths.<ref name="Gottuk-Lattimer-2-54" />

== Formation during combustion ==

Complete oxidation of carbon-containing fuel produces carbon dioxide and water. Carbon monoxide appears when oxidation is incomplete, whether because oxygen is limited, mixing is poor, the reaction is quenched or the combustion mode favours surface oxidation. Actual yields vary with material and fire conditions.<ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref><ref name="Gottuk-Lattimer-2-54" />

Early overventilated compartment fires can approach open burning, with little carbon monoxide formation in the simplified description. As the plume enters the upper layer and openings restrict airflow, underventilated fuel-rich conditions develop. Products of incomplete combustion then become much more significant.<ref name="Gottuk-Lattimer-2-55">Gottuk and Lattimer (2002), p. 2-55.</ref>
[[File:fse-carbon-monoxide-v1.svg|thumb|upright=1.5|alt=Open burning with little CO compared with fuel-rich layer producing substantial CO.|Ventilation condition changes carbon monoxide production. Based on Gottuk and Lattimer (2002), pp. 2-54–2-55.]]

The [[Equivalence ratio]] compares the available fuel-oxidiser relationship with the stoichiometric requirement for complete combustion. It helps distinguish overventilated from underventilated conditions, but local and compartment values can differ. A single room-average ratio does not describe every flame and layer region.<ref name="Gottuk-Lattimer-2-56">Gottuk and Lattimer (2002), pp. 2-56–2-57.</ref><ref name="Gottuk-Lattimer-2-57">Gottuk and Lattimer (2002), p. 2-57.</ref>

Smouldering provides a different pathway. Oxygen reacts directly with a condensed fuel surface, producing mainly carbon monoxide and carbon dioxide in proportions that depend on fuel and airflow. Ohlemiller reports examples of 6% to 7% carbon monoxide by mole in one foam experiment and 10% to 22% for cellulosic insulation under varying airflow. These are specific test results, not universal yields.<ref name="Ohlemiller-2-202">Ohlemiller (2002), p. 2-202.</ref>

Carbon monoxide can subsequently oxidise to carbon dioxide. External burning of fuel-rich gases can therefore reduce the carbon monoxide and smoke leaving a compartment, while increasing heat release outside it. The location of combustion affects both toxicity and thermal exposure.<ref name="Gottuk-Lattimer-2-55" /><ref name="Drysdale-1-95" />

== Toxic action and exposure ==

Carbon monoxide reduces the blood's ability to carry and deliver oxygen to tissues. This creates asphyxia, with confusion and possible loss of consciousness. Incapacitation can occur before death and can prevent a person from escaping, making the sublethal effects central to fire safety.<ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref><ref name="Purser-2-109-interactions">Purser (2002), pp. 2-109–2-110.</ref>

[[Fire toxicity]] concerns the adverse effects of combustion products on people. Carbon monoxide is a major contributor, but the same smoke can also contain hydrogen cyanide, low oxygen, carbon dioxide and irritants. These products can have additive or interacting effects, so assessing carbon monoxide alone can underestimate the total hazard.<ref name="Gottuk-Lattimer-2-54" /><ref name="Purser-2-109-interactions" />

[[Hydrogen cyanide]] is particularly relevant to nitrogen-containing fuels and to some smouldering polyurethane foams. Its concentration-response relationship differs from carbon monoxide, with rapid incapacitation possible at high concentrations. Purser's comparison shows why one concentration-time rule cannot be applied to every toxic gas.<ref name="Purser-2-89">Purser (2002), p. 2-89.</ref><ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>

Carbon dioxide can increase ventilation and thereby the uptake of carbon monoxide and other inhaled products. It also has its own asphyxiant effects at elevated concentrations. Low oxygen adds another pathway to hypoxia, so the complete atmosphere matters.<ref name="Purser-2-109">Purser (2002), p. 2-109.</ref><ref name="Purser-2-109-interactions" />

== Concentration, time and dose ==

A concentration describes how much carbon monoxide is present in the gas at a particular time and place. A dose combines this exposure with time and breathing response. Toxic-effect prediction therefore requires a time history rather than a single peak concentration.<ref name="Purser-2-88" />

Gottuk and Lattimer state that concentrations as low as 4,000 ppm can be fatal in less than an hour, while full-scale compartment fires can reach several percent by volume. These observations demonstrate the potential severity but do not provide a universal lethal threshold for every person and exposure.<ref name="Gottuk-Lattimer-2-54" />

Purser's analysis of active monkeys gives approximately 26,600 ppm·min for 1,000 ppm, 28,097 ppm·min for 2,000 ppm, 26,868 ppm·min for 4,000 ppm and 26,086 ppm·min for 8,000 ppm as Ct products associated with incapacitation. The roughly constant Ct relationship applies to that model and endpoint, not to every human or fire atmosphere.<ref name="Purser-2-88" />

Longer exposures do not always follow a simple constant-concentration-times-time rule. Uptake depends on breathing rate and the difference between inhaled and body concentrations. Purser illustrates that the inhaled concentration needed for a lethal carboxyhemoglobin level at four hours differs from the proportion predicted by Haber's rule.<ref name="Purser-2-88" />

Activity changes breathing and therefore uptake. Carbon dioxide can also drive hyperventilation, increasing the dose of other inhaled products. Any dose assessment should consequently state the assumed person, activity and atmosphere rather than treating dose as only elapsed time.<ref name="Purser-2-109" /><ref name="Purser-2-88" />

== Fractional effective dose ==

[[Fractional effective dose|fractional effective dose]] (FED) is a modelling method that divides the dose received during each time interval by the dose predicted to cause a selected effect. The fractions are summed until they reach one, when the model predicts incapacitation or death. Different toxic gases and endpoints require their own relationships.<ref name="Purser-2-88" />

For carbon monoxide, the Ct product can be nearly constant over particular ranges, making the method comparatively direct. For carbon dioxide, hydrogen cyanide and low oxygen, concentration has a stronger influence on the time-effect relationship. Their fractional effective dose (FED) calculations therefore differ from a simple universal Ct constant.<ref name="Purser-2-88" /><ref name="Purser-2-89" />

Purser combines selected asphyxiant contributions using explicit assumptions about additivity and interaction. Direct carbon-dioxide incapacitation, immediate irritant effects and heat do not automatically belong in that same sum. A reference value of one describes the chosen model endpoint, while a design assessment may use a lower acceptance level for the population considered.<ref name="Purser-2-110">Purser (2002), p. 2-110.</ref><ref name="Purser-2-111">Purser (2002), pp. 2-111–2-112.</ref>

The method depends on the changing gas concentrations supplied by a fire model. In Purser's theoretical CFAST example, a fixed well-ventilated yield gives an effective dose of about 0.1 after 200 s, compared with about one when vitiated yields develop. This comparison concerns the stated compartment simulation and does not establish a general exposure time for room fires.<ref name="Purser-CFAST">Purser (2002), pp. 2-96–2-97.</ref>

=== A one-minute dose calculation ===

Purser presents a simplified carbon-monoxide contribution for short fire exposures. In the form below, it represents a person undertaking light activity, with a respiratory minute volume of 25 L/min and a reference incapacitating carboxyhaemoglobin level of 30%. That percentage expresses how much haemoglobin is bound to carbon monoxide.<ref name="Purser-2-102">Purser (2002), p. 2-102.</ref><ref name="Purser-CO-step">Purser (2002), pp. 2-110–2-111.</ref>

The concentration-dependent rate is multiplied by the exposure interval. Concentration must be entered in parts per million by volume and time in minutes; the coefficient incorporates those units and the selected breathing rate.<ref name="Purser-CO-step" />
<math display="block">\Delta F_{\mathrm{CO}}=\frac{8.2925\times10^{-4}C_{\mathrm{CO}}^{1.036}}{30}\,\Delta t</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\Delta F_{\mathrm{CO}}</math> || Carbon-monoxide dose fraction added during the interval || dimensionless
|-
| <math>C_{\mathrm{CO}}</math> || Inhaled carbon-monoxide concentration || ppm by volume
|-
| <math>\Delta t</math> || Exposure duration at that concentration || min
|}

The concentration of 2,000 ppm appears in Purser's mixed-gas example. Considering only its carbon-monoxide term for one minute gives a contribution of approximately 0.0727, or 0.073. This result does not include hydrogen cyanide, oxygen depletion or increased breathing caused by carbon dioxide.<ref name="Purser-CO-step" />

The number is a fraction of the model's reference dose, not a 7.3% probability of incapacitation. Contributions accumulate during the exposure, and the complete mixed-gas method includes interactions. A small isolated time-step value consequently cannot establish acceptable conditions for the remaining exposure.<ref name="Purser-2-110" /><ref name="Purser-2-111" />

The simplified uptake approximation is intended for short, relatively high-concentration exposures. Purser explains that longer exposures at lower concentrations depart from the near-linear uptake assumption as uptake and elimination approach equilibrium. Activity, body size and physiological characteristics also affect uptake, so one coefficient does not describe every person or exposure history.<ref name="Purser-2-102" />

== Transport and smoke inhalation ==

[[Smoke inhalation]] exposes a person to carbon monoxide together with particles, other gases and heat. It can cause respiratory pain, confusion and loss of consciousness, with effects determined by the complete mixture. Carbon monoxide is often the principal asphyxiant, but not the only hazard.<ref name="Purser-2-85" /><ref name="Purser-2-86">Purser (2002), p. 2-86.</ref>

Transport can separate carbon monoxide from some particles. Van Rossum notes that soot can settle while gases spread farther through a building, allowing high carbon monoxide concentrations even where visibility remains greater than 20 m. Good visibility therefore does not demonstrate a safe atmosphere.<ref name="VR-6.1">Van Rossum (2027), §6.1.</ref>

External burning can oxidise carbon monoxide before it reaches adjacent spaces, but it does not guarantee complete removal. Underventilated compartments and external burning both change with time, so concentrations at a remote receiver need a transport and combustion model.<ref name="Gottuk-Lattimer-2-55" /><ref name="Gottuk-Lattimer-2-54" />

The source room remains important even when victims are elsewhere. Production in the compartment controls the maximum input to the building, while openings and mixing determine dilution. Assessment should follow the gas from production through transport to inhalation.<ref name="Gottuk-Lattimer-2-54" />
[[File:fse-carbon-monoxide-v2.svg|thumb|upright=1.5|alt=CO moves from source room through openings to a remote person with separate dose clock.|Carbon monoxide exposure connects source, transport and receiver. Based on Gottuk and Lattimer (2002), p. 2-54 and Purser (2002), p. 2-88.]]

== Yields and measurement ==

A carbon monoxide yield expresses the mass of carbon monoxide produced per mass of fuel consumed. It must be measured under conditions that represent the intended combustion mode. Well-ventilated and vitiated yields can differ by more than an order of magnitude.<ref name="Purser-2-96">Purser (2002), p. 2-96.</ref><ref name="IFEG-2.4-11" />

Small-scale tests can provide yields for selected equivalence ratios and materials, but full-scale fires add changing ventilation, geometry and flow. Purser cautions that full-scale equivalence ratios and mass-loss histories are needed to use those data appropriately. Test results should not be applied as universal material constants.<ref name="Purser-2-96" />
[[File:fse-carbon-monoxide-v3.svg|thumb|upright=1.5|alt=After 200 seconds, FED is 0.1 for constant early yields and 1 for vitiated yields.|Yield history changes modelled incapacitation. Based on Purser (2002), pp. 2-96–2-97.]]

The 2005 guidelines identify carbon monoxide as the principal toxic species for many fires, while warning that atypical materials require other species such as hydrogen cyanide. They recommend using combustion-reaction analysis or suitable experimental data to determine source concentrations. This keeps the assessment tied to the actual fuel.<ref name="IFEG-2.4-11" />

Measurements near the fire do not automatically represent remote exposure. Deposition, mixing and external oxidation can change the atmosphere along its path. Source yield, concentration and inhaled dose are different quantities and should be reported separately.<ref name="Gottuk-Lattimer-2-54" /><ref name="VR-6.1" />

Gas concentrations also depend on the measurement basis. Removing water before analysis raises the reported dry-basis fraction relative to the wet combustion atmosphere. Gottuk and Lattimer relate them by multiplying the dry fraction by one minus the wet water-vapour fraction; mixing wet and dry results would create an artificial difference in reported production.<ref name="Gottuk-wet-dry">Gottuk and Lattimer (2002), pp. 2-56–2-57.</ref>

== Prevention and engineering assessment ==

Prevention begins with limiting ignition and fire growth, because a smaller fire produces less effluent. Adequate ventilation can reduce fuel-rich combustion, but added airflow can also increase fire growth and transport. System effects must therefore be evaluated together rather than assuming ventilation is always beneficial.<ref name="Gottuk-Lattimer-2-55" /><ref name="VR-6.6">Van Rossum (2027), §6.6.</ref>

Smoke-control measures can remove or contain contaminated gas, supporting extraction, dilution, pressurisation and containment. The 2005 guidelines identify these as broad smoke-management approaches. Their effectiveness depends on maintaining the intended pressure and flow paths during the fire.<ref name="IFEG-2.5-7">Australian Building Codes Board et al. (2005), p. 2.5-7.</ref>

Detection and alarm provide time for response before a toxic dose accumulates. Early action can change the exposure duration and the fire's later yields. The assessment should compare the time required for detection and escape with the time at which modelled incapacitation occurs.<ref name="Purser-2-85" /><ref name="Purser-2-97">Purser (2002), pp. 2-96–2-97.</ref>

Scenario selection should include developed and fuel-rich stages where relevant. A test based only on early well-ventilated combustion can miss the period producing most carbon monoxide. Sensitivity to yield, ventilation and occupant activity should be reported.<ref name="Purser-2-97" /><ref name="Gottuk-Lattimer-2-55" />

== Limits and common misunderstandings ==

Carbon monoxide is not visible evidence of fire. A clear atmosphere can still contain a hazardous concentration, particularly after particles have deposited or become diluted. Visibility and toxicity must be assessed separately.<ref name="VR-6.1" />

It is also not produced only by smouldering. Smouldering can generate high proportions, but ventilation-limited flaming is another major source. The combustion mode and oxygen supply determine the yield in both cases.<ref name="Gottuk-Lattimer-2-54" /><ref name="Ohlemiller-2-200" />

There is no single safe or lethal carbon monoxide concentration for every situation. Exposure duration, breathing rate, other gases and individual susceptibility affect the outcome. Numerical examples from animal models and fire tests must not be treated as universal human thresholds.<ref name="Purser-2-88" /><ref name="Purser-2-111" />

dilution does not necessarily remove risk. A larger smoke volume can contain lower concentrations while spreading toxic gas to more people. Assessment needs both the diluted concentration and the total transported mass over time.<ref name="Gottuk-Lattimer-2-54" /><ref name="VR-5.3">Van Rossum (2027), §5.3.</ref>

Exposure assessment should also distinguish concentration measured on a dry or wet gas basis and the corresponding mixture composition. Species production models use these definitions when converting yields into atmospheric fractions. A consistent basis is needed before concentrations from tests and models are compared.<ref name="Gottuk-Lattimer-2-56" />

The timing of external oxidation can change the apparent trend. Carbon monoxide produced inside may be measured outside before it has fully burned, or after oxidation has reduced it. Without the measurement location and travel time, the same concentration can support different interpretations of the fire.<ref name="Gottuk-Lattimer-2-55" /><ref name="Drysdale-1-95" />

Carbon monoxide's combustibility adds another scenario dimension. Fuel-rich smoke can provide a flammable atmosphere when oxygen is restored, while carbon monoxide oxidation contributes to heat release. This links toxic exposure with smoke explosion and external burning rather than treating them as unrelated outcomes.<ref name="VR-4.10">Van Rossum (2027), §4.10.</ref><ref name="Gottuk-Lattimer-2-55" />

Response measures should be evaluated for their effect on total production as well as dilution. Suppression can reduce mass loss and later effluent, but incomplete combustion can increase yield per kilogram. A lower concentration at one moment does not prove a lower accumulated dose without the full history.<ref name="VR-6.2">Van Rossum (2027), §6.2.</ref><ref name="Purser-2-97" />

For comparison between tests, material form and ignition method should be recorded alongside yield. Small samples can respond differently from composite furniture, and pilot arrangement can change early combustion. These details help explain why one material name can have different reported carbon monoxide yields.<ref name="Purser-2-96" /><ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref>

A traceable carbon monoxide assessment therefore links the fuel and combustion mode to a time-dependent source term. It then follows transport and oxidation to the receiver, where breathing and exposure duration determine dose. This structure prevents a source yield from being mistaken for an inhaled exposure.<ref name="Gottuk-Lattimer-2-54" /><ref name="Purser-2-88" />

== See also ==

* [[Smouldering]]
* [[Smoke]]
* [[Multi-sensor detector]]
* [[Haber's rule]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Smoke, Toxicity & Tenability]]

Carbon dioxide

2026-11-02T17:58:30Z

Thomas: Improve Carbon dioxide: sourced explanations, calculations and internal links (Codex)

'''Carbon dioxide''' ('''CO₂''') is a gas produced by complete oxidation of carbon-containing fuel and is a normal product of combustion. In fire atmospheres it contributes to gas expansion, heat capacity and radiation, while elevated concentrations can stimulate breathing and cause asphyxiation. Its significance therefore extends beyond being a passive end product.<ref name="Drysdale-1-92">Drysdale (2002), p. 1-92.</ref><ref name="Purser-2-108">Purser (2002), pp. 2-108–2-109.</ref>

Complete [[Combustion]] converts fuel carbon to carbon dioxide and hydrogen to water, subject to the actual reaction and combustion efficiency. Incomplete combustion instead produces carbon monoxide, soot and other partially oxidised species. The relative yields depend on fuel, oxygen supply, mixing and temperature.<ref name="Drysdale-1-92" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

Carbon dioxide is also used as an extinguishing agent in some [[Gaseous extinguishing system]] designs, where it restricts oxygen available to the fire. The same property that suppresses combustion can make the atmosphere hazardous to people at sufficient concentration. Application therefore requires distinct fire-suppression and occupancy assessments.<ref name="Grant-4-152">Grant (2002), p. 4-152.</ref><ref name="Purser-2-108" />

== Formation and fire chemistry ==

A balanced complete-combustion reaction specifies carbon dioxide and water among the stable products. Drysdale uses propane to show both the product quantities and the oxygen required for complete oxidation. The nitrogen in air accompanies these reactions and affects the gas mixture that must be heated.<ref name="Drysdale-1-92" />

The amount of carbon dioxide produced per unit fuel depends on fuel composition and the reaction pathway. Complete conversion is an ideal reference, while natural fires always include some partially oxidised products. Actual carbon dioxide yield therefore changes with material and combustion conditions.<ref name="Drysdale-1-95" /><ref name="Purser-2-96">Purser (2002), p. 2-96.</ref>

Well-ventilated conditions favour more complete oxidation and higher carbon dioxide yield relative to carbon monoxide. Fuel-rich conditions reduce complete oxidation and increase carbon monoxide and other products. External burning can later oxidise these products to carbon dioxide after they leave the compartment.<ref name="Gottuk-Lattimer-2-55">Gottuk and Lattimer (2002), p. 2-55.</ref><ref name="Gottuk-Lattimer-2-54">Gottuk and Lattimer (2002), p. 2-54.</ref>
[[File:fse-carbon-dioxide-v1.svg|thumb|upright=1.5|alt=Complete oxidation to CO₂ and water versus incomplete pathways to CO, soot and other products.|Complete and incomplete combustion products. Based on Drysdale (2002), pp. 1-92–1-95.]]

Smouldering also produces carbon dioxide alongside carbon monoxide through direct surface oxidation of char and other condensed fuel. The ratio between them varies with material and airflow. Carbon dioxide production is therefore not limited to flaming combustion.<ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref><ref name="Ohlemiller-2-202">Ohlemiller (2002), p. 2-202.</ref>

== Physical role in fire atmospheres ==

Carbon dioxide contributes to the amount and heat capacity of combustion products. Energy released by combustion heats carbon dioxide, water vapour, nitrogen and other gases, so their thermal capacities influence flame and smoke temperatures. Drysdale lists carbon dioxide heat capacity at constant pressure as 37.129 J/mol·K at 298 K and 54.308 J/mol·K at 1000 K.<ref name="Drysdale-1-92" />

At high temperatures, carbon dioxide can dissociate as part of chemical-equilibrium changes. These heat-absorbing processes help make actual flame temperatures lower than simple adiabatic estimates. The gas is therefore chemically as well as thermally relevant to fire calculations.<ref name="Drysdale-1-96">Drysdale (2002), p. 1-96.</ref>

Carbon dioxide also absorbs and emits thermal radiation in parts of the infrared spectrum. Tien and colleagues identify water vapour and carbon dioxide as important participating gases in the 1 to 100 micrometre range. This can affect radiative exchange between flames, smoke layers, boundaries and receiving objects.<ref name="Tien-1-73">Tien, Lee, and Stretton (2002), p. 1-73.</ref>

Gas expansion during heating adds to pressure-driven movement through openings. Carbon dioxide forms part of this expanding mixture, although the resulting flow depends on the total gas amount, temperature and enclosure. It should not be treated as an independent driver isolated from other combustion products.<ref name="VR-3.2">Van Rossum (2027), §3.2.</ref><ref name="VR-6.6">Van Rossum (2027), §6.6.</ref>

== Physiological effects ==

Elevated carbon dioxide causes hypercapnia, an increased concentration in the body that alters breathing and can lead to incapacitation. Purser describes gradually increasing effects from about 3% to 6%, with more severe consequences above 7% and a growing risk of unconsciousness from 7% to 10%. These are approximate source-specific exposure relationships.<ref name="Purser-2-108" />

Purser also reports likely loss of consciousness within two minutes at 10% carbon dioxide in humans. This value must not be converted into a universal threshold for every exposure, but it demonstrates the severity of short high-concentration exposure. Concentration and duration still need to be assessed together.<ref name="Purser-2-108" />

Carbon dioxide stimulates ventilation, increasing breathing rate and volume. This can increase the uptake of carbon monoxide, hydrogen cyanide and lung irritants. The gas therefore affects both the person directly and the dose received from other smoke components.<ref name="Purser-2-109">Purser (2002), p. 2-109.</ref><ref name="Purser-2-109-interactions">Purser (2002), pp. 2-109–2-110.</ref>
[[File:fse-carbon-dioxide-v2.svg|thumb|upright=1.5|alt=CO₂ increases breathing while CO, HCN, irritants and low oxygen enter the same person.|CO₂ affects breathing and the uptake of other smoke products. Based on Purser (2002), pp. 2-108–2-110.]]

[[Oxygen depletion]] adds a separate hypoxic pathway. Carbon dioxide can accumulate while oxygen availability falls, and each change affects the fire atmosphere. Assessing carbon dioxide alone would omit the effects of reduced oxygen and the other combustion products.<ref name="Gottuk-Lattimer-2-54" /><ref name="Purser-2-109-interactions" />

== Concentration and exposure time ==

Carbon dioxide does not follow Haber's simple constant-concentration-times-time rule. Purser contrasts approximate Ct products of 20%·min at 10% carbon dioxide and 175%·min at 5%, showing that concentration strongly affects time to incapacitation. A long low exposure and a short high exposure cannot be interchanged using one constant.<ref name="Purser-2-108" />

[[Fractional effective dose|fractional effective dose]] (FED) for carbon dioxide therefore uses a concentration-dependent incapacitation relationship. Fractional doses are accumulated through time until the selected model predicts incapacitation. The method requires a stable or increasing concentration history, or another appropriate treatment of changing conditions.<ref name="Purser-2-108" /><ref name="Purser-2-109" />

Purser's worked example uses 5% carbon dioxide for 20 minutes followed by 9% for 2 minutes. The calculation below gives an accumulated fraction of about 1.01 at 22 minutes, corresponding to the model's severe-incapacitation endpoint. This is a worked application of the stated relationship, not a general exposure limit.<ref name="Purser-2-109" />
[[File:fse-carbon-dioxide-v3.svg|thumb|upright=1.5|alt=Five percent CO₂ for 20 minutes then 9 percent for 2 minutes gives FED 1.01.|Worked carbon-dioxide exposure example with FED 1.01. Based on Purser (2002), p. 2-109.]]

Purser treats direct carbon-dioxide incapacitation separately from its enhancement of other-gas uptake. In his combined asphyxiant model, increased breathing modifies the carbon-monoxide and hydrogen-cyanide contributions, while oxygen depletion is evaluated through its own relationship. Adding a direct CO₂ dose indiscriminately to every other dose would not reproduce that model.<ref name="Purser-2-111">Purser (2002), pp. 2-111–2-112.</ref>

The timing of carbon dioxide exposure matters because fire growth changes both concentration and breathing demand. A person can initially inhale a dilute mixture and later encounter a much richer layer, while activity increases ventilation. Evaluating those periods separately is more defensible than averaging them into one exposure.<ref name="Purser-2-109" /><ref name="Purser-2-97">Purser (2002), pp. 2-96–2-97.</ref>

Different exposure metrics should remain attached to their purpose. Yield describes production, concentration describes the atmosphere at one place, and FED describes a modelled physiological outcome. Converting between them requires transport, breathing and dose-effect assumptions rather than a simple unit change.<ref name="Purser-2-88">Purser (2002), p. 2-88.</ref><ref name="Purser-2-108" />

Carbon dioxide measurements should also be interpreted with the oxygen measurement. Elevated carbon dioxide and low oxygen can occur together in a developed fire, and their physiological effects differ. Reporting only one concentration can make the atmosphere appear better characterised than it is.<ref name="Gottuk-Lattimer-2-54" /><ref name="Purser-2-109-interactions" />

For fire-suppression analysis, the relevant questions include initial concentration, retention time and leakage. A nominal agent quantity can fail to maintain the required atmosphere when openings and bypass flows continue. These same processes also influence the exposure of anyone remaining in or entering the protected space.<ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref><ref name="Ohlemiller-2-207">Ohlemiller (2002), p. 2-207.</ref>

Model review should test the effect of external oxidation. Fuel-rich gases can leave the source room and produce carbon dioxide outside, changing both the source-room measurement and the external hazard. Assigning all of that carbon dioxide to the original compartment would give an inconsistent mass balance.<ref name="Gottuk-Lattimer-2-55" /><ref name="Drysdale-1-95" />

A traceable report therefore identifies the combustion mode, source yield, transport path, receiver concentration and exposure duration. It also distinguishes suppression performance from human tenability. These details allow carbon dioxide to be assessed as a combustion product, radiant gas, asphyxiant and extinguishing agent without confusing their different criteria.<ref name="Purser-2-108" /><ref name="Grant-4-152" />

[[Fire toxicity]] includes both asphyxiant and irritant effects. Carbon dioxide contributes primarily as an asphyxiant and breathing stimulant, while other products can injure airways, impair oxygen transport or prevent oxygen use in tissues. The combined mixture determines the exposed person's response.<ref name="Purser-2-85">Purser (2002), pp. 2-85–2-86.</ref><ref name="Purser-2-109-interactions" />

Carbon monoxide reduces oxygen carriage, while hydrogen cyanide reduces the ability of tissues to use delivered oxygen. Carbon dioxide can increase the uptake of both and adds its own acidotic and asphyxiant effects. A hazard model based on one gas at a time can therefore underestimate the combined condition.<ref name="Purser-2-109-interactions" />

The complete exposure also includes heat and irritant smoke. These can impair vision and breathing and increase the time needed to escape. Longer exposure in a carbon dioxide-rich atmosphere then increases the accumulated dose.<ref name="Purser-2-85" /><ref name="Purser-2-86">Purser (2002), p. 2-86.</ref>

Post-exposure effects matter as well. Purser describes evidence that carbon dioxide can enhance acidosis and lung injury after severe exposures in rodents. Such findings reinforce that removal from the atmosphere does not necessarily end physiological effects.<ref name="Purser-2-109" />

=== Calculating the direct carbon-dioxide contribution ===

Purser gives a concentration-dependent estimate of time to incapacitation by carbon dioxide. Concentration is entered as the numerical percentage by volume, so 5% is entered as 5. Each exposure interval contributes its duration divided by the incapacitation time at that interval's concentration.<ref name="Purser-CO2-model">Purser (2002), pp. 2-108–2-109.</ref>
<math display="block">t_I(C)=\exp(6.1623-0.5189C),\qquad F_{\mathrm{CO_2}}=\sum_j\frac{\Delta t_j}{t_I(C_j)}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>C_j</math> || Carbon-dioxide concentration during interval j || % by volume
|-
| <math>t_I</math> || Modelled time to incapacitation at a fixed concentration || min
|-
| <math>\Delta t_j</math> || Duration of interval j || min
|-
| <math>F_{\mathrm{CO_2}}</math> || Accumulated direct carbon-dioxide dose fraction || dimensionless
|}

For 5% carbon dioxide, the relationship gives approximately 35.4 min; for 9%, it gives approximately 4.45 min. Retaining unrounded intermediate values, the two intervals contribute 20/35.4385 and 2/4.44687. Their sum is approximately 1.01, matching the example reported by Purser.<ref name="Purser-CO2-model" />

The model reaches its reference endpoint when the accumulated fraction reaches one. That value describes the selected physiological endpoint; it is not a probability of injury and does not mean that lower fractions have no effect. Breathing changes and interaction with other fire gases can occur before direct carbon-dioxide incapacitation.<ref name="Purser-2-108" /><ref name="Purser-2-109" />

Purser specifies stable or increasing concentrations for this treatment. A decreasing exposure can involve recovery and cannot automatically be represented by the same simple accumulation. The relationship also concerns direct carbon-dioxide effects, so the calculation does not assess the complete toxicity of a fire atmosphere.<ref name="Purser-CO2-model" />

== Use in fire suppression ==

Carbon dioxide can suppress fire by reducing oxygen available to the reaction zone. This is one of the traditional smothering mechanisms, distinct from cooling, fuel removal and chemical inhibition. Effective application requires the gas to reach and remain around the relevant fire region.<ref name="Grant-4-152" />

Deep-seated and porous fires require particular attention. In small-scale grain-silo tests described by Ohlemiller, carbon dioxide fed from the bottom was the most effective of the agents examined. That result belongs to the tested configuration and does not prove effectiveness for every enclosure or fire.<ref name="Ohlemiller-2-207" />

Hot fuel can reignite when oxygen returns before cooling is complete. Smothering therefore has to be maintained long enough to prevent renewed reaction, and concealed regions must actually receive the agent. Bypass channels can leave smouldering zones untreated.<ref name="Ohlemiller-2-206" /><ref name="Ohlemiller-2-207" />

Occupancy hazards remain even when suppression is successful. Elevated carbon dioxide can stimulate breathing and cause incapacitation, while oxygen depletion adds further risk. System evaluation must therefore distinguish the concentration required for suppression from conditions tolerable to people.<ref name="Purser-2-108" /><ref name="Purser-2-109-interactions" />

== Measurement and modelling ==

A carbon dioxide yield gives the mass produced per unit fuel consumed and depends on combustion mode. Well-ventilated and vitiated test conditions can produce different yields, so the intended fire stage must be represented. Generic complete-combustion values are not a substitute for those data.<ref name="Purser-2-96" />

Source yield is not the same as concentration at a receiver. Plume entrainment, vent flow, mixing and external oxidation change the atmosphere during transport. A model must connect the source with the exposed location and the exposure duration.<ref name="Gottuk-Lattimer-2-54" /><ref name="Gottuk-Lattimer-2-55" />

Gas measurements also need appropriate units. Volume fraction, molar fraction and mass concentration require consistent treatment with the gas mixture and model. Ct products in Purser's examples use percentages by volume and time, which should not be confused with mass-based yields.<ref name="Purser-2-88" /><ref name="Purser-2-108" />

Radiation and temperature models need corresponding gas properties. Heat capacity and emissivity vary with temperature and wavelength, and simplified constant values apply only to their stated range. Source data should not be extrapolated silently to unrelated conditions.<ref name="Drysdale-1-92" /><ref name="Tien-1-73" />

== Prevention and engineering use ==

Limiting ignition and fire growth reduces the total carbon dioxide produced along with other effluent. Smoke-control measures can then remove, dilute or contain the contaminated atmosphere. The resulting concentration and exposure duration at occupied locations must be evaluated.<ref name="IFEG-2.5-7">Australian Building Codes Board et al. (2005), p. 2.5-7.</ref><ref name="Gottuk-Lattimer-2-54" />

Ventilation can support more complete combustion and reduce carbon monoxide while increasing carbon dioxide production and total fire growth. This illustrates why a lower carbon monoxide hazard does not automatically make the overall atmosphere safe. Fire development and gas composition must be considered together.<ref name="Gottuk-Lattimer-2-55" /><ref name="Purser-2-108" />

For suppression design, agent distribution and retention are as important as the nominal quantity. Openings and bypass paths can change concentration over time and allow reignition. The model should include these dynamics rather than assuming a single uniform fill.<ref name="Ohlemiller-2-206" /><ref name="Ohlemiller-2-207" />

== Limits and common misunderstandings ==

Carbon dioxide is not harmless simply because it is a normal combustion product. High concentrations can cause rapid incapacitation, and moderate concentrations can increase uptake of other toxic products. Exposure conditions determine the hazard.<ref name="Purser-2-108" /><ref name="Purser-2-109-interactions" />

It is also not a direct measure of complete fire efficiency. Carbon dioxide forms in complete and incomplete combustion, and external oxidation can create it away from the original flame. Its presence alone does not establish that all fuel burned completely.<ref name="Drysdale-1-95" /><ref name="Gottuk-Lattimer-2-55" />

The gas is not merely an inert diluent in every fire model. It absorbs and emits radiation, affects heat capacity and stimulates breathing. These physical and physiological effects can be important alongside its quantity.<ref name="Tien-1-73" /><ref name="Drysdale-1-92" /><ref name="Purser-2-109" />

suppression with carbon dioxide does not guarantee permanent extinction or occupant safety. Reignition can follow oxygen readmission, and the resulting atmosphere can be dangerous. Both outcomes require separate evaluation.<ref name="Ohlemiller-2-206" /><ref name="Purser-2-108" />

This separation also helps prevent false reassurance. More complete oxidation can reduce carbon monoxide while producing carbon dioxide and heat, and successful smothering can create an atmosphere unsuitable for people. Each outcome needs its own evidence and acceptance conditions.<ref name="Gottuk-Lattimer-2-55" /><ref name="Purser-2-109-interactions" />

== See also ==

* [[Carbon monoxide]]
* [[Hydrogen cyanide]]
* [[Tenability criteria]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Grant, C. C. (2002). Halon design calculations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Purser, D. A. (2002). Toxicity assessment of combustion products. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Tien, C. L., Lee, K. Y., & Stretton, A. J. (2002). Radiation heat transfer. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Smoke, Toxicity & Tenability]]

Hot gas layer

2026-11-02T17:58:23Z

Thomas: Improve Hot gas layer: sourced explanations, calculations and internal links (Codex)

A '''hot gas layer''' is an upper region of heated combustion products and entrained air that forms when a fire plume collects beneath a ceiling or other boundary. It can sit above a cooler lower layer, creating a stratified compartment. The layer transports and stores energy and smoke while affecting radiation, vent flow and conditions throughout the enclosure.<ref name="VR-6.7">Van Rossum (2027), §6.7.</ref><ref name="Quintiere-3-162">Quintiere (2002), p. 3-162.</ref>

The layer is fed by plume entrainment and loses mass and energy through openings and boundary heat transfer. Its temperature, depth and composition therefore change with fire growth and ventilation. It is not simply a stationary cloud of products generated directly by the fuel.<ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref><ref name="Quintiere-3-163">Quintiere (2002), p. 3-163.</ref>

Hot gas layers are relevant to smoke filling, flashover, structural heating and tenability. They are also a central feature of two-zone fire models, which assign uniform properties to the upper and lower regions as an approximation.<ref name="Cadorin-Franssen-399">Cadorin and Franssen (2003), pp. 399–400.</ref><ref name="VR-9.1">Van Rossum (2027), §9.1.</ref>

== Formation by plume and ceiling jet ==

A fire plume rises because hot gases are less dense than surrounding air. Turbulence entrains additional air, increasing mass flow and diluting the rising combustion products. This process supplies a much larger smoke flow than fuel mass loss alone would produce.<ref name="VR-5.3">Van Rossum (2027), §5.3.</ref><ref name="IFEG-2.5-2" />

A [[Ceiling jet]] forms when the plume reaches the ceiling and turns horizontally. The jet spreads hot gases beneath the surface and transfers heat to it and to nearby devices. Its interaction with walls and openings helps establish the upper layer.<ref name="IFEG-2.5-2" /><ref name="VR-5.3" />
[[File:fse-hot-gas-layer-v1.svg|thumb|upright=1.5|alt=Plume and ceiling jet feed a hot upper layer above cooler air with wall and vent losses.|Formation of a hot gas layer in a two-zone compartment. Based on Quintiere (2002), pp. 3-162–3-163.]]

The upper layer grows as plume mass and energy enter it. In a two-zone representation, the plume pumps material from the lower zone into the upper zone. Vent flows and wall losses can remove mass and energy, so layer development depends on the net balance.<ref name="Quintiere-3-162" /><ref name="Quintiere-3-163" />

Free-plume relations no longer apply unchanged once the plume enters the hot layer. Ceiling-jet or zone methods are then required to describe transport and exposure. Treating the layer as an extension of a free plume would mix different regimes.<ref name="Heskestad-2-1">Heskestad (2002), p. 2-1.</ref>

== Temperature, density and composition ==

Layer temperature results from convective energy input, radiation, boundary losses and mixing with cooler gas. It is not equal to flame temperature. Entrained air lowers temperature while increasing the total mass and volume of smoke.<ref name="VR-5.3" /><ref name="IFEG-2.5-2" />

The hot layer is less dense than the cooler gas below, which supports stratification. Temperature and composition influence this density contrast, while pressure differences at openings drive exchange with adjacent spaces. The layer can therefore remain above the lower region while still flowing through vents.<ref name="VR-3.2">Van Rossum (2027), §3.2.</ref><ref name="IFEG-2.5-6">Australian Building Codes Board et al. (2005), p. 2.5-6.</ref>

Composition includes combustion products and entrained air. Soot, carbon monoxide, carbon dioxide, water vapour and unburnt pyrolysis products can be present, depending on fuel and combustion conditions. Their concentrations affect toxicity, visibility and radiation.<ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref><ref name="Tien-1-73">Tien, Lee, and Stretton (2002), p. 1-73.</ref>

Two-zone models assign uniform temperature and composition to each layer. Real layers have gradients and fluctuations, particularly near the plume and room edges. Model outputs therefore represent averages whose usefulness depends on geometry and mixing.<ref name="VR-9.2">Van Rossum (2027), §9.2.</ref><ref name="Quintiere-3-162" />

=== Converting layer mass to volume ===

Van Rossum approximates the density of air at about one atmosphere by dividing 353 by its absolute temperature. This provides a simple connection between the mass supplied by a plume model and the volume occupied by the layer. It treats the smoke mixture as air for the density calculation.<ref name="VR-9.3">Van Rossum (2027), §9.3.</ref>
<math display="block">\rho\approx\frac{353}{T},\qquad V=\frac{m}{\rho}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\rho</math> || Approximate gas density at one atmosphere || kg/m³
|-
| <math>T</math> || Absolute gas temperature || K
|-
| <math>V</math> || Layer volume || m³
|-
| <math>m</math> || Mass in the layer, including entrained air || kg
|}

At 20 °C, or 293.15 K, the approximation gives 1.20 kg/m³. At 200 °C, or 473.15 K, it gives 0.746 kg/m³. A given mass therefore occupies more volume when hot, even before additional entrained air is included.<ref name="VR-3.2" /><ref name="VR-9.3" />

For a rectangular room with a horizontal layer, depth is layer volume divided by floor area. Van Rossum's shop example has a 20 m by 15 m floor and a 4 m ceiling. A 1.5 m deep upper layer occupies 450 m³, leaving the idealised interface 2.5 m above the floor.<ref name="VR-6.5">Van Rossum (2027), §6.5.</ref>

The 2.5 m result follows from geometry; it is not a tenability limit or an evacuation-time result. The calculation does not specify layer temperature, toxic-gas concentrations or the time needed to accumulate that volume. Those quantities require the fire history, plume flow, exhaust and heat transfer.<ref name="VR-6.5" /><ref name="VR-7.7">Van Rossum (2027), §7.7.</ref><ref name="VR-9.3" />

The density approximation also has a defined scope. Large departures from atmospheric pressure or a composition unlike air require a more appropriate gas relation. In a changing fire, temperature and mass evolve together, so constant mass or constant density cannot be assumed without a corresponding model condition.<ref name="VR-3.2" /><ref name="Quintiere-3-163" />

== Layer interface and neutral plane ==

The layer interface is the conceptual boundary between upper hot smoke and the cooler lower region. In a stable two-zone model, limited mixing occurs across it except through defined flows. Its height changes as smoke enters and leaves the upper layer.<ref name="Cadorin-Franssen-399" /><ref name="Quintiere-3-163" />

The [[Neutral plane]] is instead the height around which pressure-driven flow through an opening changes direction. Hot gas can leave above it while cooler air enters below. The 2005 guidelines note that neutral-plane height is often near the smoke-layer interface but is not identical to it.<ref name="IFEG-2.5-6" />
[[File:fse-hot-gas-layer-v2.svg|thumb|upright=1.5|alt=Smoke interface and neutral plane at different heights with hot outflow and cool inflow.|Layer interface and neutral plane are related but not identical. Based on Australian Building Codes Board et al. (2005), p. 2.5-6.]]

This distinction prevents a smoke-concentration boundary from being used as a pressure boundary without checking. Their positions respond to different physical variables, although they influence one another. Opening flow should be evaluated using the appropriate pressure and density description.<ref name="IFEG-2.5-6" />

A descending interface can expose more of the room to smoke and increase the layer's contact with walls and contents. If it approaches the lower region or floor, a two-zone approximation can become less meaningful. OZone uses an interface-height criterion among its possible switch conditions.<ref name="Cadorin-Franssen-413">Cadorin and Franssen (2003), p. 413.</ref>

== Smoke filling and reservoirs ==

[[Smoke filling]] is the accumulation of smoke in an enclosure as plume input exceeds removal. The layer descends when more mass enters than leaves, while sufficient exhaust can stabilise or reverse that movement. Fire growth and vent operation therefore shape the time history.<ref name="VR-9.3" /><ref name="IFEG-2.5-2" />

A [[Smoke reservoir]] is a volume in which hot smoke collects, such as an upper region of a compartment or a larger atrium-like space. Its size affects how much smoke can accumulate before conditions at lower levels change. The plume and exhaust must still be analysed rather than assuming unlimited capacity.<ref name="VR-6.8">Van Rossum (2027), §6.8.</ref><ref name="IFEG-2.5-7">Australian Building Codes Board et al. (2005), p. 2.5-7.</ref>

Excessive extraction at one point can cause plug holing, where clean air from below the smoke layer is drawn through the outlet. This wastes part of the exhaust capacity and is easier with a thin layer. Van Rossum describes multiple smaller outlets, a thicker layer or altered flow direction as ways to address the effect.<ref name="VR-6.8" />
[[File:fse-hot-gas-layer-v3.svg|thumb|upright=1.5|alt=Left, exhaust removes hot layer; right, plug holing draws clean air from below.|Plug holing reduces effective smoke extraction. Based on Van Rossum (2027), §6.8.]]

Natural and mechanical exhaust also change the pressure field and make-up-air requirement. An exhaust rate without a compatible air-supply path cannot be evaluated properly as a smoke-layer balance. The complete enclosure and openings must be included.<ref name="VR-6.8" /><ref name="IFEG-2.5-7" />

== Radiation and flashover ==

The hot layer radiates to lower objects and room surfaces. Its temperature, emissivity, geometry and participating gases influence the heat flux received below. Heated walls and ceiling can add further radiation, strengthening compartment-wide feedback.<ref name="VR-5.4">Van Rossum (2027), §5.4.</ref><ref name="Tien-1-73" />

[[Flashover]] is associated with this widespread heating and subsequent ignition of combustible materials. Van Rossum uses an upper-layer temperature of 500 °C as one example criterion, corresponding to approximately 20 kW/m² in his stated calculation. Many materials pyrolyse rapidly under that exposure.<ref name="VR-4.7">Van Rossum (2027), §4.7.</ref>

Collected studies show broader criteria. Cadorin and Franssen report upper-layer temperatures of 450 to 800 °C and heat fluxes of 15 to 33 kW/m², with most temperatures between 600 and 700 °C. Their OZone default of 500 °C is an average-layer model value rather than a near-ceiling measurement.<ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

Flashover can change the layer representation itself. A two-zone stratified model can give way to a one-zone mixed model, but the transition does not make real properties perfectly uniform. The model criterion and its averaging basis must be reported.<ref name="Cadorin-Franssen-400">Cadorin and Franssen (2003), pp. 400–401.</ref><ref name="VR-9.1" />

== Tenability and exposure ==

[[Tenability criteria]] describe conditions used to assess whether people can remain or escape through a space. Hot-layer temperature, radiation, visibility and toxic gases all contribute. Exposure duration and whether people are below or within the smoke are also relevant.<ref name="VR-7.7" />

The height of the layer interface is only one part of this assessment. A person below the layer may still receive radiation from it, while local mixing can introduce smoke into the lower region. A clear geometric space beneath an idealised layer therefore does not establish acceptable exposure.<ref name="VR-7.7" /><ref name="VR-9.2" />

Radiation depends on both layer temperature and the properties of the emitting region. Van Rossum illustrates conservative calculations using unit emissivity and a full view of the hot layer. Those assumptions define an idealised exposure and do not give one temperature limit applicable to every enclosure.<ref name="VR-7.7" /><ref name="VR-5.4" />

When the smoke becomes mixed throughout the occupied region, visibility and inhaled-gas exposure become especially relevant. Criteria selected for a stratified two-layer situation cannot automatically represent that mixed atmosphere. The applicable assessment method defines the exposure quantities and their acceptance conditions.<ref name="VR-7.7" />

== Structural and boundary exposure ==

The layer heats ceilings, walls and structural members through convection and radiation. Conduction then distributes energy through those solids, affecting unexposed surfaces and material properties. Layer temperature alone does not determine the member's response.<ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref><ref name="Cadorin-Franssen-400" />

Boundary losses also affect the fire. Energy entering the construction reduces the energy remaining in the gas, while hot boundaries can later radiate back to the compartment. This two-way exchange belongs in the layer energy balance.<ref name="VR-5.1">Van Rossum (2027), §5.1.</ref><ref name="Cadorin-Franssen-400" />

Openings at different heights expose different layer regions to adjacent spaces. Outflow can remove hot smoke, while inflow can supply cooler air and alter stratification. The layer therefore connects local compartment heating with building-wide smoke and heat spread.<ref name="IFEG-2.5-6" /><ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>

== Modelling and uncertainty ==

Two-zone models calculate average layer properties using conservation of mass and energy. Submodels provide plume input, vent exchange, combustion and wall losses. This structure makes the causes of layer growth and cooling explicit.<ref name="Quintiere-3-162" /><ref name="Quintiere-3-163" />

Dynamic models update these properties as fire power and openings change, while stationary models evaluate selected conditions. A stationary result can be useful for a particular assessment time but does not show how the layer formed. The choice should match the required decision.<ref name="VR-9.3" />

Common limitations include uniform layers, negligible plume volume and transport time, simple geometry and restricted treatment of wind or mechanical flow. These assumptions can be poor in large, cluttered or strongly ventilated enclosures. Model review should include them alongside input uncertainty.<ref name="Quintiere-3-163" /><ref name="VR-9.2" />

Results should not be given more precision than the fire and layer data justify. Heat release rate, emissivity, interface height and vent coefficients can all be uncertain. Sensitivity analysis and safe-direction rounding help keep those limitations visible.<ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

A layer balance begins with the plume input and ends with accumulation and outflow. Fuel mass, entrained air, vent transport and boundary energy losses must remain consistent with the chosen zone structure. This is a useful check when an estimated layer grows without a corresponding smoke source.<ref name="Quintiere-3-163" /><ref name="IFEG-2.5-2" />

Layer-average properties should be distinguished from local measurements. Gas near the ceiling, plume centreline or an opening can differ from the average assigned to a two-zone model. Using one local reading as the whole-layer value can distort radiation and vent-flow calculations.<ref name="VR-9.2" /><ref name="Cadorin-Franssen-412" />

The distinction between a measured ceiling temperature and a modelled layer-average temperature also affects radiation estimates. A local hot region near the plume can differ from the rest of the upper layer. Using it as a uniform layer temperature changes the represented emitting region and thermal exposure.<ref name="Quintiere-3-162" /><ref name="VR-9.2" />

Plug holing illustrates why outlet position and layer depth matter. If clean air reaches the exhaust from below, part of the system's capacity is spent without removing the intended smoke volume. A review should therefore check the flow field as well as the fan's nominal volumetric rating.<ref name="VR-6.8" />

Neutral-plane analysis adds a separate pressure check. Outflow above and inflow below the neutral plane can exchange mass without changing the room's total opening area. Confusing this plane with the smoke interface can lead to an incorrect explanation of the flow direction and layer development.<ref name="IFEG-2.5-6" />

Structural assessment needs the complete layer history rather than only its hottest average. Early stratification, flashover and later cooling produce different boundary exposures, and conduction continues after gas temperature declines. These stages should remain linked in a [[Compartment fire]] analysis.<ref name="Rockett-Milke-1-29" /><ref name="Cadorin-Franssen-400" />

Model outputs can be tested for sensitivity to heat release rate, interface height, vent coefficient and emissivity. These inputs affect both the layer itself and the criteria evaluated against it. A narrow result should not be presented without showing how those choices influence it.<ref name="VR-1.7" /><ref name="Quintiere-3-163" />

tenability and structural criteria should not be mixed. A layer condition used to assess escape is not automatically a structural failure criterion, and a flashover indicator is not automatically a safe-escape threshold. Each comparison needs its own stated purpose, exposure duration and jurisdiction.<ref name="VR-7.7" /><ref name="NUREG-1805-F45">U.S. Nuclear Regulatory Commission (2005), p. F-45.</ref>

Measurements used for comparison should share the same averaging basis. A thermocouple near the ceiling, an optical layer measurement and a model-layer average can respond to different aspects of the hot region. Reporting their locations and response characteristics is necessary before declaring agreement or disagreement.<ref name="Cadorin-Franssen-412" /><ref name="VR-9.2" />

A traceable layer result therefore includes the fire source, plume model, zone definition, opening history and selected criterion. It also states whether properties are local or averaged and which stage is being evaluated. These details allow the hot gas layer to be used consistently across smoke, structural and tenability assessments.<ref name="Quintiere-3-163" /><ref name="VR-9.3" /><ref name="VR-7.7" />

== See also ==

* [[Buoyancy]]
* [[Ideal gas law]]
* [[Rollover]]
* [[Smoke barrier]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Compartment fire modeling. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Tien, C. L., Lee, K. Y., & Stretton, A. J. (2002). Radiation heat transfer. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* U.S. Nuclear Regulatory Commission. (2005). ''Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program'' (NUREG-1805).
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Enclosure Fires]]

Flashover

2026-11-02T17:58:17Z

Thomas: Improve Flashover: sourced explanations, calculations and internal links (Codex)

'''Flashover''' is the rapid transition in which combustible materials throughout an enclosure ignite or become involved, changing a local fire into a fully developed compartment fire. It is associated with accelerating heat feedback, especially radiation from the hot gas layer and heated boundaries. The transition changes both the scale of burning and the conditions throughout the enclosure.<ref name="VR-4.7">Van Rossum (2027), §4.7.</ref><ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

Before flashover, the fire is generally local and fuel controlled. Afterwards, most or all combustible surfaces can be involved and ventilation commonly restricts combustion. This change can produce abundant pyrolysis gases, external flaming and much higher exposure of boundaries and occupants.<ref name="VR-4.7" /><ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>

Flashover is not defined by one universal temperature or heat release rate. Criteria based on upper-layer temperature, received heat flux, lower-zone temperature and fire power describe different measurements and models. Their source and location must accompany any threshold used in an assessment.<ref name="Cadorin-Franssen-412" /><ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref>

== Local fire to whole-compartment involvement ==

An early compartment fire can involve one object or a limited number of objects. Heat release depends largely on fuel-gas production while sufficient oxygen remains available. Hot gases rise in a plume and collect near the ceiling, forming an upper layer.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref><ref name="Quintiere-3-162">Quintiere (2002a), p. 3-162.</ref>

As that layer and surrounding surfaces become hotter, they radiate energy to contents below. Convective heating and direct flame contact can add to this exposure. Additional objects then begin to pyrolyse and ignite, increasing heat release and reinforcing the heating process.<ref name="VR-4.3">Van Rossum (2027), §4.3.</ref><ref name="Cadorin-Franssen-412" />

This feedback makes flashover a transition rather than merely one more object igniting. The enclosure becomes the driver of widespread involvement, and a local-fire description no longer represents the dominant conditions. The whole fuel inventory and its exposure become relevant.<ref name="VR-4.7" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>
[[File:fse-flashover-v1.svg|thumb|upright=1.5|alt=Local fire under a hot layer compared with widespread fire and external flames after flashover.|Flashover changes local burning into developed compartment fire. Based on Van Rossum (2027), §4.7 and §4.11.]]

[[Fire development stages]] commonly describe this as the change from growth to fully developed fire. The labels are useful for modelling, but the physical transition can be gradual in some scenarios and more abrupt in others. Ignition of every item at exactly the same instant is not required for engineering use of the concept.<ref name="VR-4.11" /><ref name="Cadorin-Franssen-412" />

== Hot gas layer and radiative feedback ==

The [[Hot gas layer]] accumulates combustion products and entrained air transported by the plume. Its temperature and depth influence the radiation received by the floor and lower objects. Heated walls and ceiling add further emission and change the net energy balance.<ref name="VR-6.7">Van Rossum (2027), §6.7.</ref><ref name="VR-5.4">Van Rossum (2027), §5.4.</ref>

Van Rossum uses an upper-layer temperature of 500 °C as one criterion, corresponding to radiation of approximately 20 kW/m² in his calculation. Many materials pyrolyse rapidly at that exposure. The example links layer temperature with floor-received heat flux rather than treating temperature as an isolated number.<ref name="VR-4.7" />

A second criterion in the same source concerns lower-zone temperatures of about 300 to 350 °C. At those conditions, many combustible materials in the lower layer can become hot enough to ignite. This describes a different measurement location from the upper-layer criterion.<ref name="VR-4.7" />

Radiation depends on more than gas temperature. Emissivity, view between surfaces, participating gases and receiver properties affect net exchange. The book's example assumes a view relationship in which upper-layer radiation also reaches floor materials, so the same temperature need not produce the same exposure in every geometry.<ref name="VR-4.7" /><ref name="VR-5.4" />

=== Relating temperature to radiant exposure ===

The Stefan–Boltzmann relation explains why radiant heating rises rapidly with temperature. For an ideal black emitting region and a black receiving surface with an unobstructed full view, net radiation is the difference between their fourth-power emissions. Temperatures in this equation are absolute temperatures in kelvin.<ref name="VR-5.4" />
<math display="block">\dot q^{\prime\prime}_{\mathrm{net}}=\sigma\left(T_h^4-T_s^4\right)</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot q^{\prime\prime}_{\mathrm{net}}</math> || Net radiant heat flux received || W/m²
|-
| <math>\sigma</math> || Stefan–Boltzmann constant, 5.67 × 10⁻⁸ || W/(m²·K⁴)
|-
| <math>T_h</math> || Absolute temperature of the hot emitting region || K
|-
| <math>T_s</math> || Absolute temperature of the receiving surface || K
|}

Using the 500 °C layer example and a 20 °C receiving surface gives 773.15 K and 293.15 K. Substitution gives approximately 19,800 W/m², or 19.8 kW/m². This explains the approximate 20 kW/m² association used in Van Rossum's introductory discussion.<ref name="VR-4.7" /><ref name="VR-5.4" />

The result depends on the idealised emitting and receiving conditions. A real smoke layer need not behave as a blackbody, and an object may see only part of it. Flames and heated walls can also contribute radiation, while convection adds a separate heat-transfer mechanism.<ref name="VR-5.4" /><ref name="VR-4.7" />

Consequently, the calculation does not establish that every room flashes over at 500 °C. Ignition also depends on the receiving materials and their preceding thermal exposure. The numerical example links temperature to an ideal radiant flux; a flashover criterion additionally defines which transition is being represented and where the temperature is measured.<ref name="VR-4.7" /><ref name="Cadorin-Franssen-412" />

== Flashover criteria ==

[[Flashover criteria]] are measurable conditions used to identify the transition in a test or model. They can include layer temperature, heat flux to fuel, lower-zone temperature and heat release rate. A criterion is a practical indicator of a complex process, not a separate law governing every compartment.<ref name="VR-4.7" /><ref name="Cadorin-Franssen-412" />

Cadorin and Franssen report upper-layer temperatures of 450 to 800 °C across collected studies, with most between 600 and 700 °C, and heat fluxes between 15 and 33 kW/m². They also note that 600 °C and about 20 kW/m² are commonly used. These ranges demonstrate uncertainty and differences between experimental definitions.<ref name="Cadorin-Franssen-412" />
[[File:fse-flashover-v2.svg|thumb|upright=1.5|alt=Temperature range 450 to 800 °C and heat-flux range 15 to 33 kW/m², with common values marked.|Collected flashover criteria and common model values. Based on Cadorin and Franssen (2003), p. 412.]]

Their OZone model uses 500 °C as its default average upper-layer criterion. The authors explain that temperatures near the ceiling can be higher than the volume-averaged layer temperature used by a two-zone model. Comparing a ceiling measurement directly with that average would mix different quantities.<ref name="Cadorin-Franssen-412" />

Heat-release criteria require equal caution. Babrauskas gives roughly 1.5 to 1.75 MW as the range where flashover can be reached for room fires ventilated through one normal-sized door. This example is tied to the test configuration and should not be treated as a universal fire-power threshold.<ref name="Babrauskas-3-1" />

== Fire growth and heat release ==

Heat release rate influences how quickly the plume and upper layer develop. Increasing power can raise gas temperature and radiative feedback, which then accelerates additional ignition. Fire growth and enclosure heating therefore form a coupled process.<ref name="Heskestad-2-2">Heskestad (2002), p. 2-2.</ref><ref name="VR-4.3" />

Design fires sometimes represent growth with a t-squared curve followed by fully developed burning and decay. These simplified curves are modelling choices for evaluation, not predictions of when flashover must occur. Incubation, object-to-object spread and changing combustion efficiency can alter the real sequence.<ref name="IFEG-1.2-29">Australian Building Codes Board et al. (2005), pp. 1.2-29–1.2-30.</ref><ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>

Fuel arrangement affects the transition. Thin or easily ignited objects can become involved earlier, while thick objects can absorb energy internally. Separation and orientation change received radiation and convective exposure, so identical total fire load can produce different development.<ref name="Kanury-2-231">Kanury (2002), pp. 2-231–2-232.</ref><ref name="Quintiere-2-247">Quintiere (2002b), p. 2-247.</ref>

Suppression during growth can prevent the developed stage. Van Rossum notes that active systems commonly intervene before flashover and can interrupt increasing heat release. Flashover is therefore not an inevitable stage of every compartment fire.<ref name="VR-4.11" />

== Rollover and backdraft ==

[[Rollover]] is a separate enclosure-fire term and should not be used interchangeably with flashover. Flashover describes widespread involvement of combustible materials, whereas the present article reserves backdraft for rapid ignition of accumulated combustible gases after oxygen enters. These labels address different mechanisms.<ref name="VR-4.7" /><ref name="VR-4.9">Van Rossum (2027), §4.9.</ref>

[[Backdraft]] requires a fuel-rich atmosphere created under oxygen restriction and a subsequent ventilation and mixing event. Flashover instead concerns the transition to widespread fuel involvement through enclosure heating. One can influence the conditions for the other, but their definitions remain distinct.<ref name="VR-4.9" /><ref name="NUREG-1805-15-4">U.S. Nuclear Regulatory Commission (2005), pp. 15-3–15-4.</ref>

A fully developed fire can have abundant pyrolysis gases and external burning, which makes these distinctions especially important. External flames alone do not identify whether the enclosure underwent flashover, backdraft or another process. The preceding history is needed.<ref name="VR-4.11" /><ref name="Drysdale-1-95" />

== Post-flashover conditions ==

A [[Post-flashover fire]] involves the whole compartment environment and is often ventilation controlled. Limited air supply can restrict internal combustion while pyrolysis continues. Unburnt gases can then burn outside openings after mixing with fresh air.<ref name="VR-4.8" /><ref name="VR-4.11" />

External flaming shifts part of the heat release to facades, adjacent spaces and neighbouring objects. It also means that heat release measured inside the compartment need not equal total heat generated by fuel originating there. System boundaries must be stated in the analysis.<ref name="Drysdale-1-95" />
[[File:fse-flashover-v3.svg|thumb|upright=1.5|alt=Pyrolysis gases leave a hot room and burn outside after mixing with fresh air.|Post-flashover combustion can occur inside and outside the room. Based on Van Rossum (2027), §4.11 and Drysdale (2002), p. 1-95.]]

Gas conditions can become more uniform, motivating one-zone rather than two-zone models. OZone switches between these representations while conserving mass and energy. The switch is a modelling approximation and does not mean that real compartment properties become perfectly uniform.<ref name="Cadorin-Franssen-399">Cadorin and Franssen (2003), pp. 399–400.</ref><ref name="Cadorin-Franssen-400">Cadorin and Franssen (2003), pp. 400–401.</ref>

High gas and surface temperatures can threaten structural elements and separating constructions. Sustained exposure after the transition can be more important for structural assessment than the short growth period. Fire resistance therefore needs the post-flashover temperature-time history.<ref name="Cadorin-Franssen-395">Cadorin and Franssen (2003), pp. 395–396.</ref><ref name="NUREG-1805-F45">U.S. Nuclear Regulatory Commission (2005), p. F-45.</ref>

== Modelling and testing ==

Zone models represent early development with hot and cool layers and developed fire with one mixed zone. Their results depend on the chosen flashover or switch criterion. Different criteria can change when the model transitions and what exposure it predicts.<ref name="Cadorin-Franssen-400" /><ref name="Cadorin-Franssen-412" />

Room-fire tests include enclosure effects that open-burning calorimetry does not capture. Hot-layer radiation and ventilation can change heat release rate significantly. Test enclosure size, openings and fuel arrangement must therefore accompany any reported flashover observation.<ref name="Babrauskas-3-1" /><ref name="Babrauskas-3-2">Babrauskas (2002), p. 3-2.</ref>

The [[Room corner test]] provides a standardised enclosure arrangement for evaluating fire development. Results from such tests belong to their method and cannot be transferred to every room without assessing scale, ventilation and fuel configuration. Flashover criteria should be identified within the test report.<ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

Glazing and openings can change during the transition. The 2005 International Fire Engineering Guidelines allow time of glass breakage to be estimated from fire severity or, in a simplified method, linked to flashover. Breakage affects both spread and ventilation, so it should not be treated as an isolated visual observation.<ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>

== Limits and common misunderstandings ==

Flashover is not a synonym for ignition. Ignition marks the start of self-sustaining combustion, while flashover is a later enclosure-scale transition. A room can have a sustained local fire for a substantial period without reaching flashover.<ref name="Kanury-2-229">Kanury (2002), p. 2-229.</ref><ref name="VR-4.7" />

It is also not the same as a backdraft or smoke explosion. Those events involve rapid combustion of a combustible gas atmosphere, while flashover concerns widespread involvement of fuel through heating. Their timing and required conditions differ.<ref name="VR-4.9" /><ref name="VR-4.10">Van Rossum (2027), §4.10.</ref>

No single temperature defines flashover in every enclosure. Average layer temperature, ceiling temperature, lower-zone temperature and received heat flux are different measurements. Reported thresholds must retain their source and measurement location.<ref name="Cadorin-Franssen-412" /><ref name="VR-4.7" />

flashover is not inevitable. Fuel depletion, suppression, insufficient heat feedback or unsuitable geometry can prevent it. Design scenarios should demonstrate why the transition is expected rather than inserting it automatically.<ref name="VR-4.11" /><ref name="IFEG-1.2-29" />

A criterion map can clarify what a model or test actually measures. Upper-layer average temperature, near-ceiling temperature, lower-zone temperature, received heat flux and total heat release rate occupy different places in the analysis. Treating them as interchangeable thresholds would confuse the evidence for the transition.<ref name="Cadorin-Franssen-412" /><ref name="Babrauskas-3-1" />

The averaging distinction is particularly relevant to two-zone models. Their upper-layer value is an average over the whole layer, not the hottest gas immediately beneath the ceiling. A criterion taken from a ceiling measurement should therefore be evaluated before being applied to that average.<ref name="Cadorin-Franssen-412" /><ref name="VR-9.2">Van Rossum (2027), §9.2.</ref>

Heat-flux criteria also depend on the receiver. View factor, surface orientation, emissivity and the temperature of surrounding surfaces affect net radiation at fuel. Two rooms with the same upper-layer temperature can therefore produce different ignition responses at their contents.<ref name="VR-5.4" /><ref name="Tien-1-75">Tien, Lee, and Stretton (2002), p. 1-75.</ref>

Fire-power criteria belong to their ventilation arrangement. Babrauskas's approximate 1.5 to 1.75 MW example concerns room flashover with one normal-sized door. Larger or smaller openings can change oxygen supply and external burning, so the same power has different implications elsewhere.<ref name="Babrauskas-3-1" /><ref name="Drysdale-1-95" />

Test selection should reflect the stage being examined. Open-burning data can describe early item behaviour without room feedback, while room tests are needed when layer radiation and ventilation alter heat release. Using only open data for a developed [[Compartment fire]] would omit a defining part of the problem.<ref name="Babrauskas-3-1" /><ref name="Babrauskas-3-3" />

Post-flashover analysis should state where combustion occurs. Fuel volatiles can burn inside, outside or in both regions, and external flames can expose facades and neighbouring objects. The model's heat-release boundary must include these locations consistently with the scenario.<ref name="Drysdale-1-95" /><ref name="VR-4.11" />

Opening changes can link several stages. Glass failure can create a new vent and flame path, alter oxygen supply and mark a change in external exposure. Using flashover as a simplified proxy for breakage is a modelling choice from the 2005 guidelines, not a universal physical equivalence.<ref name="IFEG-1.6-7" />

A final sensitivity review can vary layer criterion, fire growth, ventilation and fuel arrangement. This reveals whether the predicted transition is controlled by one assumption and whether the selected model remains valid after it occurs. The resulting time range is more informative than an unjustified single flashover time.<ref name="Cadorin-Franssen-412" /><ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

The review should also state whether flashover is an input or an output. A model can be told to switch at a selected criterion, while another analysis estimates when that criterion is reached. Confusing these approaches can make a chosen transition look like an independent prediction.<ref name="Cadorin-Franssen-400" /><ref name="Cadorin-Franssen-412" />

Evidence before and after the transition should remain separated. Pre-flashover plume and layer assumptions support local-fire analysis, while post-flashover conditions support developed exposure and external burning. Combining data from both without identifying the transition creates an inconsistent fire history.<ref name="VR-4.8" /><ref name="VR-4.11" />

A clear report therefore gives the selected criterion, its measurement basis and the resulting post-flashover treatment. It also states whether the criterion was varied and what happened to the outcome. This allows flashover to be assessed as an uncertain physical transition rather than an automatic stage label.<ref name="Cadorin-Franssen-412" /><ref name="VR-1.7" />

== See also ==

* [[Thermal radiation]]
* [[Fire spread]]
* [[Fire dynamics]]
* [[Glass breakage in fire]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002a). Compartment fire modeling. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002b). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Tien, C. L., Lee, K. Y., & Stretton, A. J. (2002). Radiation heat transfer. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* U.S. Nuclear Regulatory Commission. (2005). ''Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program'' (NUREG-1805).
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Enclosure Fires]]

Fire development stages

2026-11-02T17:58:11Z

Thomas: Improve Fire development stages: sourced explanations, calculations and internal links (Codex)

'''Fire development stages''' are the phases used to describe how a fire grows, reaches developed burning and declines. A common compartment-fire sequence distinguishes growth, fully developed fire and decay. The sequence helps organise changing heat release, smoke and ventilation, but it is not a compulsory path for every fire.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref><ref name="IFEG-1.2-29">Australian Building Codes Board et al. (2005), pp. 1.2-29–1.2-30.</ref>

The stages are linked by transitions rather than fixed durations. Ignition can be followed by smouldering or flaming, growth can stop before flashover, and developed burning can be limited by fuel or oxygen. Suppression and fuel depletion can produce several forms of decay.<ref name="VR-4.11" /><ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>

Using stages allows different analyses to focus on the relevant period. Detection and escape often depend on early development, whereas structural exposure and firefighting may be dominated by fully developed conditions. A complete assessment nevertheless needs the whole time history.<ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref><ref name="NUREG-1805-F45">U.S. Nuclear Regulatory Commission (2005), p. F-45.</ref>

== Initiation and early combustion ==

A scenario begins with an ignition source and a susceptible fuel arrangement. Gas mixtures can ignite through a pilot, liquids can produce an ignitable vapour layer, and solids can require heating and pyrolysis. The resulting combustion can be flaming, smouldering or another mode.<ref name="Kanury-2-230">Kanury (2002), p. 2-230.</ref><ref name="IFEG-2.4-4">Australian Building Codes Board et al. (2005), p. 2.4-4.</ref>

[[Smouldering]] is slow, flameless surface oxidation in a condensed fuel. It can persist for long periods with limited external signs and can produce toxic products. It may remain the dominant mode or later transition to flaming when gases, heat and oxygen conditions coincide.<ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref><ref name="Ohlemiller-2-208">Ohlemiller (2002), p. 2-208.</ref>

Early development can include an incubation or establishment phase with slow burning before a simpler growth curve applies. The 2005 International Fire Engineering Guidelines state that this duration cannot be determined reliably and is often omitted in design fires. That simplification is usually conservative because it advances modelled growth.<ref name="IFEG-2.4-11" />

The first visible flame does not prove persistent fire. Transient ignition can disappear when external heating is removed, while persistent combustion needs continuing fuel production and heat feedback. This distinction affects whether a scenario develops beyond the initiating event.<ref name="Kanury-2-230" />

== Growth and fuel-controlled burning ==

Growth involves increasing heat release, burning area or involvement of additional objects. Heat from flames and hot gases preheats new fuel, while plume transport spreads smoke and energy through the enclosure. Early spread can therefore change both fire size and the location of exposure.<ref name="Quintiere-2-246">Quintiere (2002b), p. 2-246.</ref><ref name="VR-4.3">Van Rossum (2027), §4.3.</ref>
[[File:fse-fire-development-stages-v1.svg|thumb|upright=1.5|alt=Fire stages with local growth, widespread developed burning and fuel-depletion decay.|Fire development stages and their typical conditions. Based on Van Rossum (2027), §4.11.]]

A [[Fuel-controlled fire]] has sufficient oxygen for current combustion, so fuel-gas production controls heat release. Early local fires commonly have this form because the surrounding enclosure still contains ample oxygen. Fuel type, geometry and heat feedback then dominate development.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref>

A [[t-squared fire]] represents growth as proportional to time squared. Common categories use times to 1 MW of 75 seconds for ultrafast, 150 for fast, 300 for medium and 600 for slow growth. These categories provide a simple design-fire family rather than a prediction of natural fire timing.<ref name="VR-4.5">Van Rossum (2027), §4.5.</ref><ref name="IFEG-2.4-11" />
[[File:fse-fire-development-stages-v2.svg|thumb|upright=1.5|alt=Ultrafast 75, fast 150, medium 300 and slow 600 seconds to 1 MW.|T-squared growth categories by time to 1 MW. Based on Van Rossum (2027), §4.5.]]

Actual growth can depart from quadratic behaviour. Object-to-object delays, changing combustion efficiency and ignition of different materials can produce steps or plateaus. A simplified curve should be justified by test data, scenario evidence or a deliberately conservative choice.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="IFEG-2.4-11" />

=== Reading a quadratic growth curve ===

Van Rossum describes growth categories using the time to reach 1 MW. With time measured from the selected start of quadratic growth, power follows the square of the elapsed-time ratio. Writing the reference power explicitly avoids confusing megawatts with kilowatts.<ref name="VR-4.5" />
<math display="block">\dot Q(t)=\dot Q_{\mathrm{ref}}\left(\frac{t}{t_\alpha}\right)^2,\qquad \dot Q_{\mathrm{ref}}=1\ \mathrm{MW}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot Q(t)</math> || Heat release rate at time t || MW
|-
| <math>\dot Q_{\mathrm{ref}}</math> || Reference heat release rate || MW
|-
| <math>t</math> || Elapsed time from the growth-curve origin || s
|-
| <math>t_\alpha</math> || Time to reach the reference power || s
|}

The source gives growth times of 75 s, 150 s, 300 s and 600 s for ultra-fast, fast, medium and slow growth respectively. At 150 s, the medium curve has reached 1 × (150/300)² = 0.25 MW. The fast curve has reached 1 MW at the same elapsed time.<ref name="VR-4.5" />

Energy is the area under the power curve. Integrating uninterrupted quadratic growth from its origin gives one third of the final power multiplied by the elapsed time. For the medium curve up to 300 s, this is 1 MW × 300 s ÷ 3 = 100 MJ.<ref name="VR-4.5" /><ref name="VR-9.3">Van Rossum (2027), §9.3.</ref>
<math display="block">E(t)=\int_0^t \dot Q(\tau)\,d\tau=\frac{\dot Q(t)t}{3}</math>

Here E is energy in megajoules when power is in megawatts and time is in seconds; τ denotes the integration variable. Multiplying the final 1 MW by all 300 s would instead assume the final power existed throughout growth. That constant-power assumption would describe a different fire history.<ref name="VR-9.3" />

The curve's origin need not coincide with first ignition. An establishment period can precede sustained growth, and suppression, fuel exhaustion or restricted oxygen can interrupt it. The formula therefore applies only to the selected growth interval; it does not prescribe the duration of every development stage.<ref name="VR-4.5" /><ref name="VR-4.11" />

== Hot-layer development and flashover ==

During growth, the plume carries hot gases to the ceiling and feeds an upper layer. The layer deepens and warms, exchanging radiation with lower contents and energy with boundaries. This creates a stratified compartment with hotter gas above cooler gas.<ref name="VR-6.7">Van Rossum (2027), §6.7.</ref><ref name="Quintiere-3-162">Quintiere (2002a), p. 3-162.</ref>

Radiation from the hot layer and heated surfaces can preheat many objects simultaneously. Their subsequent pyrolysis and ignition increase heat release and reinforce the feedback. This is one mechanism leading towards widespread compartment involvement.<ref name="VR-4.3" /><ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

[[Flashover]] marks the rapid transition to this widespread involvement. It is associated with upper-layer temperature and heat-flux criteria, but the source ranges are broad and measurement locations differ. A single temperature or fire power should not be used as a universal transition point.<ref name="VR-4.7">Van Rossum (2027), §4.7.</ref><ref name="Cadorin-Franssen-412" />

Flashover is not inevitable. Active suppression can interrupt growth, and insufficient heat feedback or fuel depletion can prevent the developed stage. The scenario must establish whether the required enclosure and fuel conditions exist.<ref name="VR-4.11" /><ref name="IFEG-1.2-29" />

== Fully developed and post-flashover fire ==

A [[Post-flashover fire]] has widespread fuel involvement and is commonly ventilation controlled. Abundant pyrolysis gases can be produced while openings restrict oxygen, causing incomplete combustion inside. External flames can then burn these gases after they mix with fresh air.<ref name="VR-4.8" /><ref name="VR-4.11" />

This stage changes the relevant system boundary. Heat released inside the compartment can differ from total heat generated by its fuel, and external surfaces can receive substantial exposure. Internal temperatures and structural heating can remain high for a sustained period.<ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref><ref name="NUREG-1805-F45" />

One-zone models often represent developed conditions as a uniform hot compartment, while two-zone models represent earlier stratification. The switch is a simplification of changing physical conditions. Real properties can remain non-uniform even when a one-zone approximation is useful.<ref name="Cadorin-Franssen-400">Cadorin and Franssen (2003), pp. 400–401.</ref><ref name="VR-9.1">Van Rossum (2027), §9.1.</ref>

Fully developed burning does not have to remain at one constant power. Vent changes, fuel distribution and external combustion can produce varying heat release. A steady design plateau is therefore a modelling choice rather than a universal characteristic.<ref name="VR-4.8" /><ref name="Babrauskas-3-1" />

== Decay and suppression ==

Decay can start because available fuel becomes depleted or because suppression reduces heat release. Other changes, such as restricted oxygen or altered boundaries, can also weaken combustion. The scenario should identify which mechanism is responsible.<ref name="VR-4.11" />

Fuel depletion can be spatially uneven. Some objects can burn out while others ignite later, creating several local peaks within overall decay. Treating the whole compartment as one uniformly depleted fuel package can miss this sequence.<ref name="IFEG-2.6-12">Australian Building Codes Board et al. (2005), p. 2.6-12.</ref><ref name="Quintiere-2-246" />

Suppression can cool fuel, limit oxygen or interrupt flame chemistry. Early intervention can prevent developed burning altogether, while later intervention can shorten the developed stage. Effectiveness depends on reaching the relevant reaction and fuel regions.<ref name="Grant-4-152">Grant (2002), p. 4-152.</ref><ref name="VR-4.11" />

Hot materials and smouldering fuel can remain after visible flame declines. Oxygen readmission can then cause reignition, and stored heat can continue to expose structures and occupants. Decay is therefore a stage of changing hazard, not an immediate return to safe conditions.<ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref><ref name="Gray-2-212">Gray (2002), p. 2-212.</ref>

== Compartment fires and design scenarios ==

A [[Compartment fire]] supplies the physical setting in which these stages interact. Fuel, plume, layers, openings and boundaries change together, so a stage label must be supported by modelled or observed conditions. The same label can mean different model assumptions in different methods.<ref name="Quintiere-3-162" /><ref name="Cadorin-Franssen-400" />

Schematic design fires often show growth, developed heat release and decay as a simplified curve. The 2005 guidelines identify these as conservative representations for engineering evaluation. They are not intended to reproduce every irregular natural fire.<ref name="IFEG-1.2-29" />

Smouldering design fires need a separate treatment because they may never enter developed flaming. Their source strength and transition timing can be uncertain, and many scenarios have no smouldering phase. Inserting every stage by default would therefore be inappropriate.<ref name="IFEG-1.2-29" /><ref name="IFEG-2.4-11" />

For large enclosures, spatial offsets can represent spread between regions instead of simultaneous full-area involvement. The overall curve then emerges from regional development stages. This avoids unrealistic early occupation of the entire floor.<ref name="IFEG-2.6-12" />
[[File:fse-fire-development-stages-v3.svg|thumb|upright=1.5|alt=Connected rooms and objects in growth, developed and decay stages simultaneously.|Fire stages can vary across objects and rooms. Based on Australian Building Codes Board et al. (2005), pp. 1.6-3 and 2.6-12.]]

== Investigation and evidence ==

[[Fire investigation]] uses stage evidence to reconstruct development. Burn patterns, damaged objects, opening states and the sequence of detected events can help distinguish local growth from developed burning. No single observation proves an entire timeline without its context.<ref name="Kanury-2-229">Kanury (2002), p. 2-229.</ref><ref name="NUREG-1805-F36">U.S. Nuclear Regulatory Commission (2005), p. F-36.</ref>

Later objects can become new ignition sources, so the first burning item found is not necessarily the original igniter. External flaming can likewise be a result of developed internal combustion rather than the initial event. Source and target roles change as stages progress.<ref name="NUREG-1805-F36" /><ref name="Drysdale-1-95" />

Smouldering can leave deep-seated evidence while producing little immediate flame. Central charring in a self-heating body can suggest internal runaway, but other source and preheating evidence still needs evaluation. Stage reconstruction should remain open to alternative sequences.<ref name="Gray-2-212" />

Time estimates require particular caution. Smouldering-to-flaming transitions have widely varying reported durations, and self-heating time depends strongly on size and criticality. A precise timeline should not be inferred from stage names alone.<ref name="Ohlemiller-2-208" /><ref name="Gray-2-213">Gray (2002), p. 2-213.</ref>

== Limits and common misunderstandings ==

The stages are not equal intervals and do not have standard durations. A short fire can move quickly through growth, while another can remain in early combustion for a long time. Source and scenario determine each transition.<ref name="IFEG-2.4-11" /><ref name="Ohlemiller-2-208" />

Flashover is not the beginning of fire, and decay is not the immediate end of hazard. The first stage begins with initial combustion, and residual heat and smouldering can persist through decay. These boundaries must be described by conditions, not labels alone.<ref name="VR-4.11" /><ref name="Ohlemiller-2-206" />

A design curve is not a measurement. It is a selected representation of development intended for analysis. Test data can support it, but the curve still embodies choices about growth, developed burning and decay.<ref name="IFEG-1.2-29" /><ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

one stage need not occur everywhere simultaneously. Different objects and rooms can be in different stages, especially in large or connected spaces. The overall assessment should preserve this spatial variation.<ref name="IFEG-2.6-12" /><ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref>

Growth-category times should not be mistaken for stage durations. The 75, 150, 300 and 600 second values in the t-squared family describe time to 1 MW, not time to flashover, developed burning or extinction. A scenario still needs a later-stage model and a fuel or suppression outcome.<ref name="VR-4.5" /><ref name="IFEG-2.4-11" />

Early detection depends on the same development history. A slow establishment phase can delay detectable smoke or heat, while a faster growth curve can bring them forward. Omitting that phase changes the predicted response time and should be acknowledged when the result supports alarm or evacuation decisions.<ref name="IFEG-2.4-11" /><ref name="IFEG-2.5-2" />

The transition from fuel control to ventilation control is another scenario-specific event. It depends on oxygen demand and opening flow rather than on a fixed point in every fire. A stage model should show when and why this limitation begins, especially if unburnt gases and external flaming become important.<ref name="VR-4.8" /><ref name="Drysdale-1-95" />

Spatial development complicates stage labels further. One object can be in decay while another begins to pyrolyse, and one room can be fully developed while the next has only local smoke. A building-wide timeline should therefore be assembled from object and compartment sequences rather than from one global stage label.<ref name="IFEG-2.6-12" /><ref name="IFEG-1.6-3" />

Test data can anchor parts of this timeline. Open calorimetry can describe an item's heat release, while room tests add layer and ventilation effects. Choosing data from the wrong arrangement can shift both the predicted growth and the onset of developed burning.<ref name="Babrauskas-3-1" /><ref name="Babrauskas-3-3" />

Incident reconstruction benefits from the same separation. Alarm times, visible flame reports, window failure and external flaming can be compared with candidate stages, but each observation needs its physical meaning. External flames, for example, can indicate developed internal combustion rather than initial ignition.<ref name="Drysdale-1-95" /><ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>

Evidence should also be assigned to the correct spatial region. A room can show developed burning while an adjacent corridor has only smoke transport, and these observations should not be merged into one compartment stage. Mapping evidence to objects and spaces helps preserve the actual sequence.<ref name="IFEG-1.6-3" /><ref name="IFEG-2.6-12" />

Model stages should be compared with evidence at the same times. A predicted layer average, heat release rate or opening state can be checked against measurements only when their definitions match. This avoids declaring a model correct because two different quantities happen to have similar values.<ref name="Cadorin-Franssen-412" /><ref name="Babrauskas-3-1" />

The final timeline should distinguish observed transitions from modelling choices. A flashover criterion, for example, can be selected to switch model zones even when the exact physical transition is uncertain. Recording that distinction prevents a numerical switch from being presented as a directly observed event.<ref name="Cadorin-Franssen-400" /><ref name="Cadorin-Franssen-412" />

Residual conditions belong in the final stage assessment. Stored heat can sustain boundary exposure, and hot porous fuel can react again after oxygen returns. The end of a design heat-release curve is therefore not automatically the end of the safety analysis.<ref name="Ohlemiller-2-206" /><ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref>

Where the sequence is uncertain, alternatives can be compared rather than forcing one timeline. Different incubation durations, growth rates, opening times and decay assumptions reveal which conclusions remain stable. This approach also shows which additional observation would most improve the reconstruction.<ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

Stage analysis is most useful when it preserves these distinct questions and the transitions between them. It allows early, developed and residual hazards to be assessed with appropriate data, instead of treating one design point as the entire fire. That makes the sequence and its limitations clear to the reader.<ref name="VR-4.11" /><ref name="IFEG-1.2-29" />

== See also ==

* [[Smouldering-to-flaming transition]]
* [[Design fire]]
* [[Heat release rate]]
* [[Fire load]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Grant, C. C. (2002). Halon design calculations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002a). Compartment fire modeling. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002b). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* U.S. Nuclear Regulatory Commission. (2005). ''Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program'' (NUREG-1805).
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Enclosure Fires]]

Compartment fire

2026-11-02T17:58:04Z

Thomas: Improve Compartment fire: sourced explanations, calculations and internal links (Codex)

A '''compartment fire''' is a fire whose development is influenced by an enclosure, its boundaries and its openings. Fuel, combustion and heat release interact with hot gas layers, ventilation and heated surfaces. These interactions distinguish compartment behaviour from an otherwise similar fire in the open.<ref name="Quintiere-3-162">Quintiere (2002), p. 3-162.</ref><ref name="VR-4.8">Van Rossum (2027), §4.8.</ref>

The compartment can amplify heat feedback by retaining hot gases and radiation. It can also restrict oxygen, causing incomplete combustion and fuel-gas accumulation. Fire development therefore depends on the room as well as the fuel package.<ref name="VR-4.3">Van Rossum (2027), §4.3.</ref><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

Compartment-fire analysis supports estimates of smoke conditions, flashover, structural exposure and spread to adjacent spaces. It requires a time-dependent description of the fire source, plume, openings and boundary heat transfer. The enclosure can therefore be as influential as the initial fuel package in determining when conditions become hazardous.<ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref><ref name="IFEG-1.6-7">Australian Building Codes Board et al. (2005), p. 1.6-7.</ref>

== Fire source, plume and enclosure ==

The fire source supplies energy, fuel gases and combustion products. Its heat release rate depends on material decomposition, mass loss and combustion efficiency. A fuel inventory alone does not specify this source because heat release rate varies with ignition, spread and ventilation.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="VR-4.5">Van Rossum (2027), §4.5.</ref>
[[File:fse-compartment-fire-v1.svg|thumb|upright=1.5|alt=Fire plume feeds an upper layer while vents and walls exchange mass and energy.|Compartment fire as a coupled mass and energy system. Based on Quintiere (2002), pp. 3-162–3-163.]]

A buoyant plume rises from the source and entrains room air. The plume increases in mass flow while becoming more diluted, then transports mass and energy towards the ceiling. Its behaviour depends on heat release, source geometry and restrictions such as walls.<ref name="Heskestad-2-1">Heskestad (2002), p. 2-1.</ref><ref name="IFEG-2.5-2" />

At the ceiling, the flow turns into a ceiling jet and begins to form an upper layer. The enclosure thus changes a vertical plume into horizontal smoke movement and boundary heating. Free-plume relationships no longer apply unchanged once the plume enters this layer.<ref name="Heskestad-2-1" /><ref name="VR-5.3">Van Rossum (2027), §5.3.</ref>

Walls, floor and ceiling receive energy by convection and radiation and conduct part of it away. These losses influence gas temperature while heating the construction. Boundary conditions therefore connect compartment fire dynamics with structural and separating performance.<ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref><ref name="Cadorin-Franssen-400">Cadorin and Franssen (2003), pp. 400–401.</ref>

== Fire development stages ==

[[Fire development stages]] commonly include growth, fully developed burning and decay. They provide a useful sequence for describing changing fire power and enclosure conditions, but not every fire passes through every stage. Suppression, fuel depletion or unsuitable heat feedback can end development earlier.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>

During early growth, the fire is often local and fuel controlled. Sufficient oxygen is available, so heat release depends mainly on fuel-gas production and spread. Hot gases accumulate above a cooler lower layer, producing a stratified enclosure.<ref name="VR-4.8" /><ref name="Cadorin-Franssen-399">Cadorin and Franssen (2003), p. 399.</ref>

As additional objects ignite, heat release and upper-layer temperature can increase. Radiation from hot gases and heated boundaries preheats more fuel, producing stronger feedback. This can lead to flashover, although it is not inevitable.<ref name="VR-4.3" /><ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

Decay follows fuel depletion or suppression and can include a prolonged period of hot surfaces and smouldering. The end of open flaming does not immediately remove heat or reignition hazards. Compartment conditions therefore remain important after peak power.<ref name="VR-4.11" /><ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref>

== Hot gas layer and stratification ==

The [[Hot gas layer]] is the upper region of heated smoke and entrained air fed by the plume. A two-zone model represents it as having uniform temperature and composition above a cooler lower zone. These uniform properties are modelling assumptions rather than exact room measurements.<ref name="Quintiere-3-162" /><ref name="VR-9.1">Van Rossum (2027), §9.1.</ref>

The layer affects occupants and objects through hot gases, reduced visibility, toxicity and radiation. It also exchanges heat with walls and ceiling and supplies gas to openings. Layer depth, temperature and composition therefore influence several fire-safety outcomes simultaneously.<ref name="VR-6.7">Van Rossum (2027), §6.7.</ref><ref name="IFEG-2.5-2" />

A stable interface can separate upper and lower regions in the model. Real interfaces can be disturbed by mixing, obstacles, vent flows and plume pulsations. Strong mixing can instead produce approximately homogeneous conditions that are better represented by one zone.<ref name="VR-9.2">Van Rossum (2027), §9.2.</ref><ref name="Cadorin-Franssen-400" />

The plume acts as a pump transferring mass from lower to upper zone. Conservation of mass and energy tracks this input alongside vent flow, fuel supply and boundary losses. This system view prevents the layer from being treated as an independent smoke reservoir.<ref name="Quintiere-3-162" /><ref name="Quintiere-3-163">Quintiere (2002), p. 3-163.</ref>

== Fuel and ventilation control ==

A fuel-controlled fire has enough oxygen for its current fuel-gas production, so fuel properties and exposed area dominate heat release. Early local fires commonly have this form. The same applies to outdoor fires in the source's basic description because oxygen is not restricted by an enclosure.<ref name="VR-4.8" />

A [[Ventilation-controlled fire]] is limited by oxygen availability. Restricted openings can prevent enough fresh air entering and enough smoke leaving, so heat release depends on ventilation flow rather than fuel inventory alone. Unburnt pyrolysis gases can then accumulate.<ref name="VR-4.8" />

The transition between these forms depends on fire size and opening conditions. A growing fire can move from fuel control to ventilation control as its oxygen demand increases. Door and window changes can reverse or alter this balance during the incident.<ref name="VR-4.8" /><ref name="IFEG-1.6-7" />
[[File:fse-compartment-fire-v2.svg|thumb|upright=1.5|alt=Open room with sufficient oxygen compared with restricted room and unburnt gases outside.|Fuel-controlled and ventilation-controlled fires. Based on Van Rossum (2027), §4.8.]]

Some volatile gases can leave the compartment and burn outside when they meet fresh air. This external flaming shifts heat release and exposure beyond the enclosure. Total heat generated by the original fuel therefore need not equal heat released within the room.<ref name="Drysdale-1-95" />

=== An opening-based power estimate ===

For a ventilation-controlled fire, Drysdale estimates the incoming air mass flow from the effective opening area and height. If all oxygen in that air is consumed inside, the internal heat release follows from the energy released per unit mass of air. This is a restricted natural-ventilation approximation, not a general prediction for arbitrary openings or mechanical systems.<ref name="Drysdale-1-95" />
<math display="block">\dot m_a\approx0.52A_v\sqrt{h_v},\qquad \dot Q_{\mathrm{inside}}\approx\dot m_a H_a</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot m_a</math> || Incoming air mass flow || kg/s
|-
| <math>A_v</math> || Effective ventilation opening area || m²
|-
| <math>h_v</math> || Opening height || m
|-
| <math>H_a</math> || Heat released per mass of air consumed; approximately 3,000 || kJ/kg
|-
| <math>\dot Q_{\mathrm{inside}}</math> || Estimated heat release inside the compartment || kW
|}

Babrauskas describes a room-fire test doorway 0.8 m wide and 2.0 m high. Using that geometry as an illustration gives an opening area of 1.6 m². The air-flow approximation gives 0.52 × 1.6 × √2 = 1.18 kg/s, and the corresponding internal power is approximately 3.53 MW.<ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref><ref name="Drysdale-1-95" />

The calculation assumes enough fuel is available to consume the incoming oxygen. It can overestimate a fuel-controlled fire, where excess air passes through without supporting additional combustion. It also leaves out heat released by fuel gases burning beyond the compartment opening.<ref name="Drysdale-1-95" />

This 3.53 MW result is not the power required for flashover. Flashover concerns enclosure-wide heating and ignition, whereas the calculation estimates a ventilation-limited burning rate. Boundary heat losses, fuel placement and thermal feedback remain necessary to describe the transition and the gas temperature.<ref name="Drysdale-1-95" /><ref name="VR-4.7">Van Rossum (2027), §4.7.</ref><ref name="Quintiere-3-163" />

== Flashover and post-flashover fire ==

[[Flashover]] is the rapid transition towards ignition of combustible materials throughout the compartment. Radiation from the upper layer and heated boundaries can drive widespread pyrolysis and ignition. The enclosure then moves from local to fully developed involvement.<ref name="VR-4.7" />

The transition is associated with criteria such as upper-layer temperature and received heat flux, but no single universal threshold exists. Cadorin and Franssen report broad experimental ranges and distinguish near-ceiling measurements from layer averages. Model criteria must be interpreted accordingly.<ref name="Cadorin-Franssen-412" />

A [[Post-flashover fire]] commonly involves abundant pyrolysis gases and ventilation-limited combustion. External flaming can be prominent, and boundaries experience sustained high temperatures. This stage is particularly relevant to structural fire resistance and fire service exposure.<ref name="VR-4.11" /><ref name="NUREG-1805-F45">U.S. Nuclear Regulatory Commission (2005), p. F-45.</ref>
[[File:fse-compartment-fire-v3.svg|thumb|upright=1.5|alt=Stratified local fire develops into a hot compartment with flames leaving openings.|Local and developed compartment-fire representations. Based on Cadorin and Franssen (2003), pp. 399–401 and Van Rossum (2027), §4.11.]]

One-zone models approximate this developed state as a uniform hot compartment, while two-zone models represent earlier stratification. Switching between them is a modelling choice that should conserve mass and energy. Real rooms do not necessarily become perfectly mixed at the same instant.<ref name="Cadorin-Franssen-400" /><ref name="VR-9.1" />

== Compartmentation and spread ==

[[Fire compartmentation]] uses enclosing constructions to limit fire and smoke spread between spaces. Its performance depends on barrier integrity, stability, conduction and openings. A compartment fire tests all of these functions through heat, pressure and combustion products.<ref name="IFEG-1.6-7" />

Conduction can expose combustibles on the unexposed side without visible barrier failure. Cracks and failed firestopping can allow flames and hot gases through, while collapse creates larger openings. These routes require separate timing and assessment.<ref name="IFEG-1.6-7" />

Openings also control the fire within the original compartment. Doors and windows change oxygen supply, pressure and external flaming, so their state affects both development and spread. Evacuation and fire service actions can therefore alter the fire scenario.<ref name="VR-4.8" /><ref name="IFEG-1.6-7" />

Adjacent spaces can become new compartments with their own plumes and layers. The time of spread determines when their design fires begin and when evacuation or intervention conditions change. Compartment analysis is thus part of a building-wide sequence rather than a single-room calculation.<ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref>

== Fire dynamics and modelling ==

[[Fire dynamics]] supplies the physical framework for compartment analysis. Fuel chemistry and decomposition provide the source, heat transfer provides feedback, and buoyancy and pressure drive transport. A compartment model combines these rather than treating any one as the complete fire.<ref name="Drysdale-1-90">Drysdale (2002), p. 1-90.</ref><ref name="VR-1.6">Van Rossum (2027), §1.6.</ref>

Zone models divide the enclosure into uniform regions and apply conservation laws to each. Submodels describe plume entrainment, combustion, vents and wall heat transfer. They can efficiently estimate average conditions when the assumed zones and geometry remain appropriate.<ref name="Quintiere-3-162" />

Many zone models neglect plume volume and transport time, treat contents heat capacity as negligible and use simplified pressure and friction assumptions. These choices can matter in large, cluttered or rapidly changing compartments. The user must assess their effect rather than treating model output as direct observation.<ref name="Quintiere-3-163" />

OZone combines two-zone and one-zone representations with coupled wall calculations and several combustion options. It illustrates how a model can cover localised and developed fires, but its default criteria are informative rather than universal. Application still requires scenario-specific inputs and review.<ref name="Cadorin-Franssen-399" /><ref name="Cadorin-Franssen-412" />

Conservation provides a first review of any compartment model. Fuel and entrained air entering the system should be balanced by accumulation and outflow, while combustion energy should appear in gases, boundaries, radiation or other modelled losses. An impossible inventory can indicate an inappropriate vent or plume assumption.<ref name="Quintiere-3-163" />

Model selection should follow the physical state. Two zones can represent a stratified local fire, while one zone can represent a more uniform developed fire. Switching because a criterion is convenient rather than physically appropriate can change layer temperature and exposure without a valid reason.<ref name="Cadorin-Franssen-400" /><ref name="VR-9.1" />

Opening data require care because geometric and effective flow areas differ. Van Rossum describes contraction and obstacles reducing the effective opening through which gas passes. Using the measured open area without the relevant coefficient can therefore overestimate the available ventilation path.<ref name="VR-6.8">Van Rossum (2027), §6.8.</ref>

Fire-source data should be matched to the enclosure question. Open-burning tests omit room feedback, while room tests include it and can produce different heat release. A compartment model should not silently use one as though it were the other.<ref name="Babrauskas-3-1" /><ref name="Babrauskas-3-2">Babrauskas (2002), p. 3-2.</ref>

Sensitivity analysis can test heat release rate, opening size, layer criterion and boundary properties. These inputs affect both the timing of developed conditions and the resulting exposure. A conclusion that reverses after a plausible change should be reported with that dependence.<ref name="VR-1.7">Van Rossum (2027), §1.7.</ref><ref name="Cadorin-Franssen-412" />

The output should then be compared with the appropriate performance measure. Smoke-layer height and composition support tenability assessment, gas and wall temperatures support structural assessment, and spread timing supports compartmentation review. These outputs should not be substituted for one another.<ref name="IFEG-1.6-3" /><ref name="IFEG-2.5-2" />

Validation is strongest when the comparison uses the same physical arrangement and measured quantity. A near-ceiling temperature is not directly comparable with a layer average, and an open-calorimeter curve is not directly comparable with a room-fire curve. Matching these definitions is part of model evaluation.<ref name="Cadorin-Franssen-412" /><ref name="Babrauskas-3-1" />

Smoke assessments use compartment models to estimate layer height, temperature, composition and vent flow. Detector and sprinkler studies use plume and ceiling-jet exposure, while structural studies use gas and boundary temperatures. These outputs serve different decisions and require suitable time resolution.<ref name="IFEG-2.5-2" /><ref name="Cadorin-Franssen-395">Cadorin and Franssen (2003), pp. 395–396.</ref>

Evacuation analysis compares changing compartment conditions with the time occupants need to respond and escape. Structural analysis may instead focus on sustained developed exposure. A single design time or peak value cannot represent every purpose without checking its relevance.<ref name="IFEG-1.6-3" /><ref name="NUREG-1805-F45" />

Comparisons with tests can reveal missing physics or inappropriate data. Cadorin and Franssen compare OZone with full-scale tests to evaluate its compartment model, while noting the assumptions behind its submodels. Validation is therefore tied to scenario and submodel quality.<ref name="Cadorin-Franssen-395" />

== Limits and common misunderstandings ==

A compartment fire is not just a larger open fire placed indoors. The enclosure changes heat retention, oxygen supply and the location of combustion. The same fuel can consequently produce different heat release and exposure histories.<ref name="Babrauskas-3-1" /><ref name="VR-4.8" />

A hot upper layer is not perfectly uniform in reality. Temperature and composition vary between plume and room edges, and interfaces can mix. Uniform zones are useful approximations whose suitability depends on the compartment.<ref name="VR-9.2" />

Flashover is not guaranteed to occur, and a fully developed fire is not always fuel limited. Fuel can be abundant while oxygen controls heat release. Describing the fire only by inventory misses this distinction.<ref name="VR-4.11" /><ref name="VR-4.8" />

external flames do not mean the original compartment fire has ended. They can be part of its developed stage, fed by gases produced inside. The whole connected system must be assessed.<ref name="Drysdale-1-95" /><ref name="VR-4.11" />

Documentation should make the model boundaries visible. The fire source, gas zones, vents and wall surfaces each have inputs and outputs, and external combustion may require another region. Identifying those boundaries prevents internal heat release, total fuel energy and adjacent-space exposure from being combined incorrectly.<ref name="Drysdale-1-95" /><ref name="Quintiere-3-163" />

== See also ==

* [[Fuel-controlled fire]]
* [[Fire-induced pressure]]
* [[Zone model]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Compartment fire modeling. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* U.S. Nuclear Regulatory Commission. (2005). ''Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program'' (NUREG-1805).
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Enclosure Fires]]

Backdraft

2026-11-02T17:57:58Z

Thomas: Improve Backdraft: sourced explanations, calculations and internal links (Codex)

A '''backdraft''' is the rapid or explosive ignition of accumulated combustible pyrolysis gases when oxygen suddenly enters an oxygen-limited enclosure. The event requires a sufficient fuel-gas inventory and an ignitable condition, followed by ventilation and mixing that create a combustible mixture. Hot expanding gases can be expelled through the new opening as a fireball.<ref name="VR-4.9">Van Rossum (2027), §4.9.</ref><ref name="NUREG-1805-F7">U.S. Nuclear Regulatory Commission (2005), p. F-7.</ref>

Backdraft develops from the history of the enclosure rather than from the opening alone. A fire first consumes oxygen and produces combustible gases faster than they can burn. Opening a door, window or other vent then changes the atmosphere and allows the delayed reaction to propagate.<ref name="VR-4.9" /><ref name="NUREG-1805-15-4">U.S. Nuclear Regulatory Commission (2005), pp. 15-3–15-4.</ref>

The phenomenon is distinct from ordinary fire growth after ventilation. It involves rapid combustion of gases that accumulated before the venting event. Its timing depends on gas temperature, composition, mixing and the location of an effective ignition source.<ref name="NUREG-1805-15-4" />

== Conditions that accumulate fuel gas ==

Pyrolysis and incomplete combustion produce combustible gases and aerosols. In an enclosure with restricted oxygen, not all of these products can burn at the location where they are produced. They can therefore accumulate in a hot smoke layer while pyrolysis continues.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref><ref name="NUREG-1805-15-4" />
[[File:fse-backdraft-v1.svg|thumb|upright=1.5|alt=Oxygen-limited room accumulates fuel gas, a door opens and mixed gases ignite explosively.|Backdraft follows accumulation and a ventilation change. Based on Van Rossum (2027), §4.9 and U.S. Nuclear Regulatory Commission (2005), p. F-7.]]

The fire consumes oxygen as it burns. Limited air inflow and restricted smoke outflow then lower the oxygen concentration, suppressing further gas-phase combustion without necessarily stopping decomposition. Fuel-rich conditions can consequently develop even while substantial chemical energy remains in the enclosure.<ref name="VR-4.8" /><ref name="VR-3.1">Van Rossum (2027), §3.1.</ref>

Heat retention is another part of the setup. Hot gases and heated surfaces continue to support decomposition, while the oxygen-poor atmosphere prevents complete oxidation. The result is a combination of elevated temperature and unburnt fuel that can become hazardous when air is introduced.<ref name="VR-4.9" />

A sufficiently large gas inventory is needed for a severe event. A small amount of unburnt vapour can ignite without producing the same fireball or pressure effect. The enclosure volume, fuel production history and duration of restricted ventilation therefore matter.<ref name="NUREG-1805-F7" /><ref name="VR-4.9" />

== Ventilation-controlled fire ==

A [[Ventilation-controlled fire]] is limited by oxygen availability rather than only by fuel-gas production. Openings restrict the supply of fresh air, so heat release rate becomes coupled with the flow through them. Excess pyrolysis gases can remain unburnt and move to other parts of the enclosure or outside.<ref name="VR-4.8" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

This condition differs from a fuel-controlled fire, where sufficient oxygen is available and the rate of fuel-gas production controls development. Early local fires are commonly fuel controlled, while fully developed compartment fires are often ventilation controlled. The transition depends on enclosure and opening conditions.<ref name="VR-4.8" />

Ventilation control does not mean combustion stops everywhere. Flames can persist where oxygen remains available, while other regions produce unburnt gases. Some of those gases may burn externally after mixing with air, and some can accumulate for a later backdraft.<ref name="Drysdale-1-95" /><ref name="VR-4.9" />

The location of the reaction is therefore important. Fuel can be pyrolysed in one part of the enclosure, transported in smoke and ignited elsewhere after mixing. A backdraft assessment must follow both gas production and gas movement rather than focusing only on the original flame.<ref name="VR-3.1" /><ref name="NUREG-1805-15-4" />

== Opening and mixing ==

Sudden opening introduces oxygen-rich air into the enclosure. Where this air mixes with fuel-rich smoke in suitable proportions, a premixed combustible region can form. An ignition source within that region can then initiate rapid flame propagation.<ref name="NUREG-1805-F7" />

If the gas layer is already at its ignition condition, ignition can occur immediately when oxygen arrives. NUREG-1805 also describes delayed cases, particularly with a cooler gas layer. Fresh air then needs time to mix with the fuel-rich layer and reach a hot fire source before ignition occurs.<ref name="NUREG-1805-15-4" />
[[File:fse-backdraft-v2.svg|thumb|upright=1.5|alt=Hot layer ignites immediately; cooler layer ignites only after air mixes back to fire.|Immediate and delayed backdraft pathways. Based on U.S. Nuclear Regulatory Commission (2005), pp. 15-3–15-4.]]

This delay means that no fireball at the moment of opening does not prove the atmosphere is safe. Mixing and transport can create the required conditions later. The flame itself can become the ignition source once the mixture reaches it.<ref name="NUREG-1805-15-4" />

The resulting event has characteristics of a premixed fuel-air deflagration. Flame travels through the combustible region rather than spreading only across the surface of the original fuel. Heat expansion can then drive burning gases out through the opening.<ref name="NUREG-1805-15-4" /><ref name="NUREG-1805-F7" />

Opening shape and location influence the flow path and where mixing occurs. Multiple openings can create throughflow, while a single opening can support exchange at different heights. The detailed result depends on pressure, density and vent geometry rather than on the simple fact that a door was opened.<ref name="IFEG-2.5-6">Australian Building Codes Board et al. (2005), p. 2.5-6.</ref><ref name="VR-6.8">Van Rossum (2027), §6.8.</ref>

=== Why ignition can be delayed ===

The air entering an opening does not instantly make the whole enclosure a uniform mixture. It mixes progressively with accumulated fuel gases, while hot and cooler regions remain distinct. A combustible region may therefore form locally before the average compartment composition would suggest the same condition.<ref name="VR-4.9" /><ref name="NUREG-15-4">U.S. Nuclear Regulatory Commission (2005), p. 15-4.</ref>

NUREG-1805 describes both immediate and delayed ignition after fresh air enters. Where the gases are sufficiently hot, the incoming air and fuel mixture may ignite during mixing. With cooler gases, ignition can occur later when the combustible mixture reaches the remaining fire.<ref name="NUREG-15-4" />

This sequence explains why the opening event and the rapid burning event need not coincide. It also explains why low visible flame activity before opening is inconclusive. Oxygen starvation can reduce flaming while heat continues to generate combustible decomposition products.<ref name="VR-4.8" /><ref name="VR-4.9" />

Three aspects of the history therefore distinguish the mechanism: fuel accumulation under restricted ventilation, admission and mixing of fresh air, and subsequent ignition. A single room temperature or smoke colour does not describe all three. The introductory sources give a mechanism, rather than a universal numerical threshold that predicts the event from one measurement.<ref name="VR-4.9" /><ref name="NUREG-15-4" />

== Backdraft and smoke explosion ==

A [[Smoke explosion]] is rapid combustion of an already premixed combustible smoke atmosphere. NUREG-1805 describes smouldering fires that can produce enough unburnt fuel and carbon monoxide for such a mixture, followed by autoignition or ignition by another source. The defining feature is the prepared mixture rather than the sudden introduction of oxygen.<ref name="NUREG-1805-15-4" /><ref name="VR-4.10">Van Rossum (2027), §4.10.</ref>

Backdraft instead emphasises oxygen entering and creating the ignitable mixture after a period of restriction. The two phenomena can involve similar gases and rapid deflagration, but their sequence and mixing mechanism differ. Confusing them can hide the role of ventilation timing.<ref name="NUREG-1805-15-4" />
[[File:fse-backdraft-v3.svg|thumb|upright=1.5|alt=Comparison of ventilation-triggered backdraft, premixed smoke explosion and radiative flashover.|Backdraft, smoke explosion and flashover have different sequences. Based on Van Rossum (2027), §4.7, §4.9 and §4.10.]]

Smoke explosion also requires the mixture to lie within its flammable range and to encounter autoignition conditions or another source. Van Rossum identifies lower and upper explosion limits as relevant composition boundaries. These limits are properties of the mixture under its conditions, not universal smoke concentrations.<ref name="VR-4.10" /><ref name="Beyler-2-172">Beyler (2002), p. 2-172.</ref>

Smouldering-to-flaming transition can be one initiating route for rapid gas-phase combustion, but it is not synonymous with backdraft. A local smouldering region can ignite gases without the enclosure-scale oxygen inrush that characterises backdraft.<ref name="Ohlemiller-2-208">Ohlemiller (2002), p. 2-208.</ref><ref name="NUREG-1805-F7" />

Flames outside an opening have several possible origins. Flame extension can occur when the flame from the original fuel is longer than the available interior space. External burning can also occur when oxygen-starved fuel gases leave the room and encounter air outside.<ref name="Gottuk-layer">Gottuk and Lattimer (2002), p. 2-55.</ref>

Gottuk and Lattimer explain that flame extension is possible under either well-ventilated or under-ventilated conditions, whereas their external-burning mechanism requires an under-ventilated source. Neither description alone implies the sudden premixed combustion associated with backdraft. The location of visible flame is therefore less informative than the fuel, ventilation and ignition history.<ref name="Gottuk-layer" />

== Backdraft and flashover ==

[[Flashover]] is the rapid transition towards ignition of combustible materials throughout a compartment, strongly associated with radiative heating and rising enclosure temperature. Backdraft is instead rapid ignition of accumulated combustible gases after oxygen enters. Their initiating conditions and the material being ignited differ.<ref name="VR-4.7">Van Rossum (2027), §4.7.</ref><ref name="VR-4.9" />

A flashover can contribute to conditions that favour backdraft by increasing pyrolysis and ventilation limitation. Fully developed fires often have abundant fuel gases and restricted oxygen, and external burning can occur. The terms nevertheless remain separate descriptions of enclosure behaviour.<ref name="VR-4.8" /><ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>

Gas-layer burning, discussed under [[Rollover]], can occur at the interface between an upper layer and incoming air. Gottuk and Lattimer distinguish such burning from flames extending through an opening. Observing flames in either location does not, by itself, establish the accumulation, mixing and ignition sequence of a backdraft.<ref name="Gottuk-layer" />

These distinctions matter in assessment. Flashover criteria focus on compartment temperature and heat flux, smoke-explosion assessment focuses on a premixed atmosphere, and backdraft assessment adds the ventilation change and delayed mixing. A single label cannot replace all three analyses.<ref name="VR-4.7" /><ref name="VR-4.10" /><ref name="NUREG-1805-15-4" />

== Firefighting and ventilation ==

[[Firefighting]] changes both heat and airflow. Opening access routes, applying suppression and removing smoke can alter the oxygen and mixing conditions in the enclosure. These actions need to be evaluated against the possibility of accumulated fuel gas and delayed ignition.<ref name="VR-4.9" /><ref name="NUREG-1805-F7" />

[[Positive pressure ventilation]] uses mechanical fans to blow fresh air into an enclosure, creating a pressure difference that drives existing air and combustion products towards an exit. NUREG-1805 describes its use to influence ventilation and burning activity during firefighting. It directly changes the variable that triggers backdraft in the source definitions.<ref name="NUREG-1805-F46">U.S. Nuclear Regulatory Commission (2005), p. F-46.</ref>

The definition alone does not establish that positive pressure ventilation is safe or unsafe in a particular scenario. Its effect depends on where air is directed, how it mixes with fuel-rich gas and whether an ignition source is present. The source provides a mechanism, not a universal tactical rule.<ref name="NUREG-1805-F46" /><ref name="NUREG-1805-15-4" />

Suppression can also cool fuel and reduce further pyrolysis, while oxygen removal can temporarily suppress reaction. Hot fuel-rich material can nevertheless reignite when air returns. The atmosphere and the fuel bed therefore both need assessment before an enclosure is considered stable.<ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref><ref name="Gray-2-212">Gray (2002), p. 2-212.</ref>

== Assessment and uncertainty ==

A backdraft assessment should reconstruct the ventilation and combustion history. Relevant evidence includes enclosure volume, fuel type, heat retention, opening states and the duration of oxygen restriction. These determine whether a significant combustible inventory could accumulate.<ref name="VR-4.9" /><ref name="NUREG-1805-F7" />

Gas composition and temperature must then be considered with mixing. A fuel-rich layer can be outside the flammable range before opening and move into it only in part of the enclosure. The relevant mixture is local and time-dependent, not necessarily uniform throughout the room.<ref name="NUREG-1805-15-4" /><ref name="Beyler-2-172" />

Ignition timing remains uncertain because the mixture and source must coincide. Immediate ignition can occur in a hot layer, while a cooler layer can require transport back to the fire. A model that assumes instantaneous uniform mixing would miss the delayed case.<ref name="NUREG-1805-15-4" />

The same uncertainty prevents a universal backdraft temperature, oxygen concentration or opening time. Source definitions identify necessary elements but do not supply one threshold for every enclosure. Scenario-specific analysis is required, and unsupported numerical triggers should not be invented.<ref name="VR-4.9" /><ref name="NUREG-1805-F7" />

== Common misunderstandings ==

Backdraft is not any increase in fire size after a door opens. Ordinary ventilation-driven growth can follow improved oxygen supply without rapid combustion of a pre-existing accumulated gas charge. The accumulated inventory and rapid deflagration distinguish backdraft.<ref name="VR-4.9" /><ref name="NUREG-1805-15-4" />

It is also not simply an external flame from a ventilation-controlled fire. External flaming can burn continuously as gases leave an enclosure and mix with air. Backdraft involves rapid ignition after a ventilation change and can expel burning gases as a fireball.<ref name="Drysdale-1-95" /><ref name="NUREG-1805-F7" />

Lack of flame immediately after opening does not exclude a delayed event. Mixing can take time, and ignition can occur when the prepared region reaches a hot source. Observation needs to include the period after the opening as well as the moment itself.<ref name="NUREG-1805-15-4" />

smoke and pyrolysis gases are not harmless merely because oxygen concentration is low. Low oxygen can suppress combustion while combustible gases continue to accumulate. Restoring oxygen can create the conditions for rapid reaction.<ref name="VR-4.8" /><ref name="VR-4.9" />

The location of the ignition source determines which part of the mixed region reacts first. A glowing ember can ignite a suitable local mixture even when the wider enclosure remains too fuel-rich or too lean to propagate flame. Assessment therefore needs local composition and source evidence, not only an average room concentration.<ref name="NUREG-1805-F7" /><ref name="Beyler-2-172" />

Before opening, the atmosphere can be fuel rich because oxygen has been depleted. After opening, some regions can remain fuel rich while others enter the flammable range and still others become diluted. The backdraft region is the part where fuel, oxygen and ignition conditions coincide.<ref name="NUREG-1805-15-4" />

External flaming provides a useful contrast. It occurs when gases leaving the compartment burn after contacting outside air, whereas backdraft involves rapid combustion associated with the new ventilation and mixing event. The timing and duration of the flame behaviour help distinguish a continuing external fire from a discrete backdraft.<ref name="Drysdale-1-95" /><ref name="NUREG-1805-15-4" />

A review of opening states should include their sequence as well as their sizes. One opening can start exchange, and another can establish throughflow that changes transport and mixing. Recording when each opening changed allows these effects to be compared with the observed ignition time.<ref name="IFEG-2.5-6" /><ref name="VR-6.8" />

Firefighting assessments should likewise separate the intended purpose of ventilation from its possible effect on a prepared atmosphere. Positive pressure ventilation is defined by its pressure and flow arrangement, but the resulting mixture still has to be evaluated. The sources do not support a universal rule that one ventilation method always prevents or always causes backdraft.<ref name="NUREG-1805-F46" /><ref name="NUREG-1805-15-4" />

The NUREG-1805 examples come from a US nuclear fire-analysis document, but the described mechanisms are physical rather than plant-specific requirements. They do not provide a numerical backdraft prediction method for every building. Their appropriate use is to define the phenomenon and identify the required conditions, not to invent a universal operational threshold.<ref name="NUREG-1805-F7" /><ref name="NUREG-1805-15-4" />

A defensible report therefore distinguishes established facts from unresolved conditions. It identifies the fuel-gas source, oxygen restriction, opening event, mixing path and ignition evidence separately. Where any of these is unknown, the backdraft explanation remains a hypothesis requiring further evidence rather than a certain reconstruction.<ref name="Kanury-2-229">Kanury (2002), p. 2-229.</ref><ref name="VR-4.9" />

== See also ==

* [[Smouldering-to-flaming transition]]
* [[Flammability limits]]
* [[Equivalence ratio]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Beyler, C. L. (2002). Flammability limits of premixed and diffusion flames. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gottuk, D. T., & Lattimer, B. Y. (2002). Effect of combustion conditions on species production. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Gray, B. (2002). Spontaneous combustion and self-heating. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Kanury, A. M. (2002). Flaming ignition of solid fuels. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* U.S. Nuclear Regulatory Commission. (2005). ''Fire dynamics tools: Quantitative fire hazard analysis methods for the U.S. nuclear regulatory commission fire protection inspection program'' (NUREG-1805).
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Enclosure Fires]]

Heat release rate

2026-11-02T17:57:52Z

Thomas: Improve Heat release rate: sourced explanations, calculations and internal links (Codex)

'''Heat release rate''' ('''HRR''') is the rate at which combustion reactions produce heat. It expresses fire power, usually in kilowatts or megawatts, and describes how quickly energy is released rather than how much energy is stored in the fuel. Babrauskas identifies it as the essential quantitative characteristic of fire size.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="VR-4.5">Van Rossum (2027), §4.5.</ref>

Heat release rate changes as ignition, spread, ventilation and fuel depletion alter combustion. It influences flame height, plume flow, gas temperature and the exposure of people and structures. It therefore provides a central input to many fire-dynamics and design calculations.<ref name="Heskestad-2-1">Heskestad (2002), p. 2-1.</ref><ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref>

The quantity is related to mass loss rate and effective heat of combustion, but these need not have a constant relationship. Material decomposition, incomplete combustion and enclosure feedback can change both the rate and the energy released per unit mass.<ref name="Babrauskas-3-1" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

== Power, energy and burning rate ==

Power is energy produced per unit time, with one watt equal to one joule per second. Heat release rate can be integrated over a period to estimate energy released during that period, provided the full time history is known. A peak value alone does not specify total energy.<ref name="VR-4.5" />
[[File:fse-heat-release-rate-v1.svg|thumb|upright=1.5|alt=Heat-release curve with peak power and shaded energy area over time.|Heat release rate is power; energy is its time integral. Based on Van Rossum (2027), §4.5.]]

[[Fire load]] instead describes the chemical energy potentially available from combustible material. A high fire load can sustain a long fire but does not establish its instantaneous power. Heat release rate and fire load answer different questions and use different units.<ref name="VR-4.4">Van Rossum (2027), §4.4.</ref>

[[Burning rate]] is sometimes used informally for heat release rate, but Babrauskas recommends using that term nonquantitatively. Mass loss rate is measured in kilograms per second, while heat release rate is measured in kilowatts. Keeping the terms separate avoids confusing fuel consumption with energy production.<ref name="Babrauskas-3-1" />

[[Heat of combustion]] is the heat released by complete oxidation of a unit quantity of fuel to stable products. Effective heat of combustion accounts for actual burning conditions and can differ from the bomb-calorimeter value. Incomplete combustion means that not all available chemical energy is released.<ref name="Drysdale-1-92">Drysdale (2002), pp. 1-92–1-93.</ref><ref name="Drysdale-1-95" />

Babrauskas illustrates this variability with Western red cedar tested at 65 kW/m². Effective heat of combustion was roughly 12 MJ/kg during the first part of the test and increased to around 30 MJ/kg during the charring period. A single constant conversion would not represent that whole test.<ref name="Babrauskas-3-1" />

=== Relating mass, power and energy ===

Effective heat of combustion converts the rate of fuel consumption into released power. Unlike the theoretical heat of complete combustion, it represents the energy actually released per unit mass under the specified burning conditions. The following form uses megajoules per kilogram, so its power output is in megawatts.<ref name="Babrauskas-3-1" />
<math display="block">\dot Q=\dot m_f\Delta H_{c,\mathrm{eff}},\qquad E(t)=\int_0^t \dot Q(\tau)\,d\tau</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot Q</math> || Heat release rate || MW = MJ/s
|-
| <math>\dot m_f</math> || Fuel mass-loss rate || kg/s
|-
| <math>\Delta H_{c,\mathrm{eff}}</math> || Effective heat of combustion || MJ/kg
|-
| <math>E</math> || Energy released over the interval || MJ
|-
| <math>t,\tau</math> || Time and integration variable || s
|}

For constant power, the integral becomes power multiplied by duration. Van Rossum's smoke example assumes 1 MW for 120 s and an effective heat of combustion of 20 MJ/kg. The released energy is therefore 120 MJ, the corresponding mass-loss rate is 0.050 kg/s, and the consumed fuel mass is 6.0 kg.<ref name="VR-6.5">Van Rossum (2027), §6.5.</ref>

The same peak power could occur in a short pulse or remain approximately steady for much longer. Those histories would release different total energies even though their maximum heat release rates matched. A measured curve preserves this distinction; quoting only its peak discards the duration information.<ref name="Babrauskas-3-1" /><ref name="VR-4.5" />

The conversion assumes that the selected effective heat of combustion applies throughout the interval. If charring, oxygen supply or the composition of the released volatiles changes, the conversion may also change. An energy integral of measured power remains meaningful even when a single mass-loss conversion factor is inadequate.<ref name="Babrauskas-3-1" /><ref name="Drysdale-1-95" />

The consumed 6.0 kg is also different from the initial fuel inventory. More fuel may remain unburnt, and the example does not specify the eventual fire duration. The calculation follows one stated interval rather than predicting a complete fire from its peak power.<ref name="VR-4.4" /><ref name="VR-6.5" />

== Heat release rate per unit area ==

[[Heat release rate per unit area]] expresses power divided by burning area, commonly in kilowatts per square metre. It describes intensity over the selected area, while total heat release rate describes the whole fire. The area definition must be stated because fuel surface, flame footprint and compartment floor area are not interchangeable.<ref name="VR-4.6">Van Rossum (2027), §4.6.</ref>

A small fire can have high local intensity and low total power, while a larger fire can distribute lower intensity over a greater area. Total heat release rate increases when either area or intensity increases. This relationship helps connect object-scale measurements with design-fire size.<ref name="VR-4.6" />

Van Rossum gives an illustrative developed-building-fire value of 250 kW/m² for a non-storage building. He also gives an average living-room sofa at about 2.5 MW and a car peak of 8.5 MW. These are anchors from the source, not universal values for every sofa, car or occupancy.<ref name="VR-4.5" />

Fire area can change as flame spreads. If intensity remains broadly similar, a larger pyrolysing area can increase total power and strengthen feedback. This is one reason early object-to-object spread matters in fire development.<ref name="Quintiere-2-246">Quintiere (2002), p. 2-246.</ref>

== Growth and design fires ==

A [[Design fire]] specifies a simplified heat-release history or related fire inputs for analysis. It may include growth, developed burning and decay, or a smouldering scenario without a developed flame stage. The curve should represent a defined scenario and purpose.<ref name="IFEG-1.2-29">Australian Building Codes Board et al. (2005), pp. 1.2-29–1.2-30.</ref>

A [[t-squared fire]] uses quadratic growth, in which heat release rate increases in proportion to the square of elapsed time. Common categories are labelled by the time taken to reach 1 MW: 75 seconds for ultrafast, 150 seconds for fast, 300 seconds for medium and 600 seconds for slow growth in the cited guidance.<ref name="VR-4.5" /><ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>
[[File:fse-heat-release-rate-v3.svg|thumb|upright=1.5|alt=Times to 1 MW: ultrafast 75, fast 150, medium 300 and slow 600 seconds.|Characteristic t-squared growth times to 1 MW. Based on Van Rossum (2027), §4.5.]]

These categories are modelling choices rather than predictions of every real fire. Experiments can show an incubation or establishment phase before quadratic growth, and its duration cannot be determined reliably in the 2005 guidelines. Omitting that phase is identified there as a usually conservative design assumption.<ref name="IFEG-2.4-11" />

Developed burning can be fuel controlled or ventilation controlled. In the first case, fuel-gas production limits power while oxygen is sufficient. In the second, restricted oxygen supply limits combustion and can leave unburnt pyrolysis gases to burn elsewhere.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref>

Decay can follow fuel depletion or intervention. A design curve may select a decay rate for simplicity, but real decline can be irregular and include smouldering or external burning. Total energy and residual hazard should be assessed over the whole relevant history.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref><ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref>

== Oxygen-consumption measurement ==

The [[Oxygen consumption principle]] estimates heat release rate from the oxygen consumed during combustion. Many fuels release approximately similar energy per unit mass of oxygen consumed, allowing measurement of oxygen depletion to be converted into heat release. Carbon monoxide production can require a correction for incomplete combustion.<ref name="Drysdale-1-96">Drysdale (2002), pp. 1-95–1-96.</ref>

Drysdale gives a conversion factor of 13.1 kJ per gram of oxygen consumed for the method. This is different from heat of combustion per gram of fuel. The distinction allows diverse fuels to be compared through their oxygen use rather than their individual mass loss alone.<ref name="Drysdale-1-93">Drysdale (2002), p. 1-93.</ref><ref name="Drysdale-1-96" />
[[File:fse-heat-release-rate-v2.svg|thumb|upright=1.5|alt=Fire exhaust flowing to oxygen measurement and heat-release calculation with CO correction.|Oxygen-consumption calorimetry estimates heat release from oxygen use. Based on Drysdale (2002), pp. 1-95–1-96.]]

Open-burning calorimeters measure items without a surrounding test room. Room-fire tests instead include hot-layer and surface feedback and possible ventilation limitation. At low heat release rates these can agree, but developed room fires can differ substantially from open burning.<ref name="Babrauskas-3-1" />

Bench-scale instruments such as the cone calorimeter expose a small specimen to controlled radiant heat. They provide material-response curves but do not automatically reproduce full object geometry or enclosure effects. Intermediate and full-scale tests help address those differences when required.<ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

== Enclosure effects ==

A hot upper layer and heated room surfaces can increase radiant feedback to fuel and raise heat release rate above an open-burning value. Ventilation can simultaneously restrict oxygen and move unburnt gases to other locations. Room effects therefore depend on both thermal feedback and air supply.<ref name="Babrauskas-3-1" /><ref name="Drysdale-1-95" />

Babrauskas reports room augmentation around 20% for some upholstered chairs in fires up to 1 MW, but stronger and less predictable effects for mattresses. Liquid pools require a specific pool model rather than a simple correction. These examples demonstrate that product configuration affects the result.<ref name="Babrauskas-3-2">Babrauskas (2002), p. 3-2.</ref>

Room-fire results cannot be extrapolated directly to rooms with larger ventilation. Open-burning data can be more suitable for well-ventilated enclosures, provided fuel geometry and exposure remain comparable. The source and intended application must be matched explicitly.<ref name="Babrauskas-3-2" />

Heat released inside a compartment is not necessarily all heat generated by fuel originating there. Some volatile gases can escape and burn outside, changing both the measured internal power and the external hazard. System boundaries must therefore be stated when reporting heat release rate.<ref name="Drysdale-1-95" />

== Use in fire models ==

Plume models use heat release rate, often its convective part, to estimate entrainment, temperature and mass flow. Heskestad notes that convective flux is rarely less than 60% to 70% of total heat release in the fire types discussed. The radiative remainder acts in other directions.<ref name="Heskestad-2-2">Heskestad (2002), p. 2-2.</ref><ref name="IFEG-2.5-2" />

Smoke and detection calculations use the resulting transport to estimate when combustion products reach a layer or device. Structural calculations use the fire's heat-release history to determine boundary and member exposure. These applications need consistent timing and fire-area assumptions.<ref name="IFEG-2.5-2" /><ref name="IFEG-2.6-2">Australian Building Codes Board et al. (2005), p. 2.6-2.</ref>

A design heat-release curve can come from an appropriate test, statistical evidence or a simplified growth model. Full-scale data are valuable when they describe the actual fuel source, but even then enclosure and installation differences need review. Similar object names are not sufficient evidence of identical behaviour.<ref name="Babrauskas-3-3" />

For large spaces, spatial development can be represented by dividing the area into regions with ignition time offsets. Summing these regional heat-release histories avoids assuming simultaneous combustion of the entire floor. The offsets must still be supported by spread analysis.<ref name="IFEG-2.6-12">Australian Building Codes Board et al. (2005), p. 2.6-12.</ref>

== Interpretation and uncertainty ==

Peak heat release rate is not total fire energy, average power or fire duration. A short high peak and a long lower plateau can produce very different thermal exposures. The complete curve and the assessment period must be considered.<ref name="VR-4.5" /><ref name="VR-5.1">Van Rossum (2027), §5.1.</ref>

Combustion efficiency adds further uncertainty. Heskestad reports values close to unity for some pool fires but much lower values for polystyrene and a fully involved stack of wood pallets in the cited tests. Total heat release should not automatically be equated with theoretical complete-combustion power.<ref name="Heskestad-2-2" />

Heat release rate per unit area also needs a clear area. Multiplying an intensity by a floor area when the original measurement used burning surface area creates an inconsistent result. Units alone do not catch that definitional error.<ref name="VR-4.6" />

Rounding should reflect uncertain fuel and exposure inputs. Van Rossum recommends two or at most three significant figures for many fire-engineering outcomes and safe-direction rounding for time comparisons. Excess decimal places can suggest confidence that the underlying fire data do not support.<ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

== Interpreting test curves ==

A heat-release result should state whether it was measured or assumed. A calorimeter produces a measurement under its test conditions, while a design curve represents an analytical choice. Presenting both as an observed fire history would conceal that distinction.<ref name="Babrauskas-3-1" /><ref name="IFEG-1.2-29" />

The system boundary should also be explicit. Results can describe one item, all combustion inside a room, or all reactions caused by fuel originating there. External flaming means these totals need not be identical. A boundary description prevents internal and total fire power from being mixed.<ref name="Drysdale-1-95" />

Time averaging requires similar care. An instantaneous peak, an average over one test interval and an average over the entire fire answer different questions. Comparing them without a common interval can create a false ranking between tests or design scenarios.<ref name="VR-4.5" /><ref name="Babrauskas-3-3" />

For per-unit-area results, the reference area belongs beside every value. A table should not switch between fuel surface and floor area without renaming the quantity. This preserves the distinction between local intensity and compartment-wide energy production.<ref name="VR-4.6" />

Complete-oxidation calculations provide a useful upper reference but not an automatic measurement. Combustion efficiency and effective heat of combustion should be identified if mass loss is converted into power. Where these vary, the conversion needs a time-dependent treatment or direct heat-release measurement.<ref name="Babrauskas-3-1" /><ref name="Heskestad-2-2" />

Convective and radiative portions should likewise be identified when they are used differently. Plume calculations commonly use the convective portion, while target radiation requires the radiative portion. Applying total heat release to both without a stated split can double-count or misassign the energy.<ref name="Heskestad-2-2" /><ref name="VR-9.3">Van Rossum (2027), §9.3.</ref>

The frequently used 70% convective share is a modelling approximation rather than a universal property. Heskestad gives a broader 60% to 70% range for several fire types, and Van Rossum cautions against using the simple split in post-flashover conditions. The selected fraction should therefore be justified for the fire stage.<ref name="Heskestad-2-2" /><ref name="VR-9.3" />

Integrating a heat-release curve gives energy released over its stated interval. This can be compared with fire load to check whether the scenario consumes more or less energy than the inventory contains. Such a check can expose an inconsistent duration or an unreasonably high assumed power.<ref name="VR-4.4" /><ref name="VR-4.5" />

A peak value can occur at a different time from maximum smoke production or maximum target exposure. Entrainment, thermal storage and changing view factors influence those later outcomes. Heat release rate should therefore be carried through the model as a time-dependent input rather than replaced prematurely by its maximum.<ref name="IFEG-2.5-2" /><ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref>

a traceable report includes the heat-release curve, area definition, combustion-efficiency basis, enclosure and ventilation. It also records whether values are peak, averaged or integrated. These details allow heat release rate to be reused without losing the conditions that give it meaning. This is essential for comparison.<ref name="Babrauskas-3-3" /><ref name="VR-1.7" />

== See also ==

* [[Fire dynamics]]
* [[Fuel-controlled fire]]
* [[Car park fire]]
* [[Effective heat of combustion]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Fire Dynamics]]

Fire plume

2026-11-02T17:57:46Z

Thomas: Improve Fire plume: sourced explanations, calculations and internal links (Codex)

A '''fire plume''' is the buoyant flow of combustion products, entrained air and any flames above a localised fire. It rises because hot gases are less dense than the surrounding air, and it transports heat and smoke into the upper part of an enclosure or the outdoor atmosphere. Most fire plumes are turbulent except when the source is very small.<ref name="Heskestad-2-1">Heskestad (2002), p. 2-1.</ref><ref name="VR-6.7">Van Rossum (2027), §6.7.</ref>

The plume links fuel combustion with smoke filling, detector response, structural heating and venting. Its properties depend on heat release rate, fire geometry, air entrainment and surrounding boundaries. A free axisymmetric plume is only one configuration among several encountered in buildings.<ref name="Heskestad-2-1" /><ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref>

A plume is not simply the visible flame. The visible reacting region can occupy only its lower part, while the broader buoyant flow continues upwards with diluted combustion products and entrained air. Temperature, velocity and composition all change with height.<ref name="Heskestad-2-2">Heskestad (2002), p. 2-2.</ref>

== Buoyancy and plume formation ==

[[Buoyancy]] results from density differences between hot fire gases and cooler surrounding air. At approximately constant pressure, heating reduces gas density and produces an upward force. This force drives the rising plume and draws cooler air into the fire region.<ref name="VR-3.2">Van Rossum (2027), §3.2.</ref><ref name="VR-5.3">Van Rossum (2027), §5.3.</ref>

The combustion source can be solid, liquid or gaseous. Heat feedback releases volatiles from solids and evaporates liquids, while pressurised gas can supply fuel directly. High-pressure releases can add source momentum, changing the simple buoyancy-driven picture.<ref name="Heskestad-2-1" />

The rising flow includes both combustion products and surrounding air. Turbulent motion mixes these streams and produces a highly convoluted instantaneous boundary. A time-averaged description is therefore often more useful than treating the edge as a smooth fixed surface.<ref name="Heskestad-2-1" />

Buoyancy is a driving force, while convection is heat transfer associated with the moving gas. The plume uses both: buoyant motion creates convective transport of energy and combustion products. Wind and mechanical systems can alter or oppose that movement.<ref name="VR-5.3" /><ref name="VR-6.6">Van Rossum (2027), §6.6.</ref>

== Entrainment and dilution ==

[[Entrainment]] is the inflow of surrounding air into the plume. It increases the total mass flow as the plume rises and dilutes its temperature and combustion-product concentrations. The plume consequently becomes broader and contains a greater proportion of air.<ref name="VR-5.3" /><ref name="Heskestad-2-1" />

The 2005 International Fire Engineering Guidelines note that entrained air usually greatly exceeds burned-fuel mass flow. Some smoke-development methods therefore neglect the fuel mass term in comparison. Heat release from the fuel still drives the flow and cannot be neglected as an energy input.<ref name="IFEG-2.5-2" />

Entrainment explains why a small combustion source can generate a large smoke flow. Smoke filling is not determined only by the mass of fuel burned. Plume height, heat release rate and the perimeter available for air entrainment all influence the delivered volume.<ref name="VR-5.3" /><ref name="IFEG-2.5-2" />

Air entering from all sides supports an axisymmetric model. Walls, corners and other restrictions reduce the available entrainment perimeter and change the plume shape. Applying a free-plume relationship without adjusting for these conditions can misestimate mass flow.<ref name="IFEG-2.5-2" /><ref name="VR-6.7" />

== Flame region and mean flame height ==

The lower part of a plume can contain a diffusion flame in which fuel vapour and oxygen mix and react. Lower luminosity often appears comparatively steady, while the upper flame is intermittent. Vortex structures can form near the base and move upwards.<ref name="Heskestad-2-2" />

[[Flame height]] describes the vertical extent of this reacting region. Heskestad presents an objective mean height based on intermittency: the level where flame is present half the time. This definition gives consistent measurements and is reasonably consistent with, although slightly lower than, averages made by human observation.<ref name="Heskestad-2-2" />

Centreline temperature can remain nearly constant in the lower flame and then decay as reactions trail off and entrained air cools the flow. Velocity tends to reach a maximum near or slightly below mean flame height and then declines. These profiles make a single plume temperature or velocity unrepresentative of all heights.<ref name="Heskestad-2-2" />
[[File:fse-fire-plume-v1.svg|thumb|upright=1.5|alt=Plume with lower flame, intermittent region and diluted upper flow marked at mean flame height.|Temperature and velocity change through a fire plume. Based on Heskestad (2002), p. 2-2.]]

Mean flame height is also used to distinguish the reacting region from the overlying approximately inert plume. Its value depends on heat release rate and source diameter or related scaling, rather than being a fixed multiple for every fire. Different source regimes can produce different flame behaviour.<ref name="Heskestad-2-2" /><ref name="Heskestad-2-3">Heskestad (2002), p. 2-3.</ref>

=== Estimating mean flame height ===

Van Rossum presents the empirical mean-flame-height relation below. It combines total heat release rate with the equivalent circular diameter of the fire. The coefficient applies when power is entered in kilowatts and both lengths are expressed in metres.<ref name="VR-6.7" />
<math display="block">L=0.235\dot Q^{2/5}-1.02D,\qquad D=\sqrt{\frac{4A}{\pi}}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>L</math> || Mean flame height above the fuel surface || m
|-
| <math>\dot Q</math> || Total heat release rate || kW
|-
| <math>D</math> || Equivalent circular source diameter || m
|-
| <math>A</math> || Horizontal fire-source area || m²
|}

For illustration, Van Rossum's 1 MW fire-area example gives a burning area of 4 m². Treating that area as circular gives D = 2.26 m. Entering 1,000 kW in the relation gives a mean flame height of approximately 1.42 m.<ref name="VR-4.6">Van Rossum (2027), §4.6.</ref><ref name="VR-6.7" />

This is the mean height of the reacting region, not the total height reached by hot smoke. The plume continues above the flame, and instantaneous flame tips fluctuate around the statistical height. Heskestad defines the mean flame height by the level at which flame is present half the time.<ref name="Heskestad-2-1" />

In this example the estimated flame is shorter than the equivalent source diameter. It therefore falls on the broad-fire side of Van Rossum's approximate Heskestad-versus-Thomas model-selection convention. This comparison selects a suitable description of entrainment; it does not turn either model into a universal expression for every fire geometry.<ref name="VR-6.7" />

The free-plume treatment concerns buoyancy-dominated turbulent flow into an approximately uniform surrounding atmosphere. A high-momentum jet, a nearby wall or an existing upper smoke layer changes those conditions. The equation consequently cannot establish ceiling exposure or smoke-layer behaviour without the corresponding flow model.<ref name="Heskestad-2-1" /><ref name="Heskestad-2-2" />

== Heskestad and Thomas plume models ==

The [[Heskestad plume]] model uses heat release rate, source geometry and a virtual origin to estimate plume properties. The virtual origin is a calculated point on the plume axis that can lie above or below the fuel surface. It allows the model to represent the effective source location for entrainment.<ref name="VR-6.7" /><ref name="Heskestad-2-1" />

Heskestad's relations address flame height, plume temperature, velocity, virtual origin and entrainment. Their application assumes an axisymmetric turbulent plume in otherwise uncontaminated, uniform air unless a specific stratified treatment is included. The relations cease to apply where the plume enters a smoke layer.<ref name="Heskestad-2-1" />

The [[Thomas plume]] relates mass flow primarily to fire-source perimeter and rise height. Van Rossum explains that this makes the estimate comparatively simple and, within its stated basis, less directly dependent on fire power than other models. Perimeter and height still have to be defined consistently with the scenario.<ref name="VR-6.7" />

Van Rossum describes a rough selection in which Heskestad is more suitable for relatively small fires and Thomas for relatively large fires, based on the relationship between mean flame length and hydraulic fire diameter. This is a model-selection convention from the cited Dutch guidance, not a universal physical boundary.<ref name="VR-6.7" />
[[File:fse-fire-plume-v3.svg|thumb|upright=1.5|alt=Heskestad inputs of power and virtual origin compared with Thomas perimeter and height.|Heskestad and Thomas plume models use different input emphases. Based on Van Rossum (2027), §6.7 and Heskestad (2002), p. 2-1.]]

== Ceiling jets and upper layers ==

A [[Ceiling jet]] forms when the rising plume reaches a ceiling and turns horizontally. Hot gases then spread beneath the surface and transfer heat to it and to nearby devices. This changes both the flow direction and the relevant heat-transfer problem.<ref name="VR-5.3" /><ref name="IFEG-2.5-2" />

The jet interacts with walls, openings and the developing upper layer. It can feed a hot gas layer above a cooler lower layer, creating thermal stratification. Plume entrainment then becomes a mass and energy source for that layer.<ref name="VR-6.7" /><ref name="Quintiere-3-162">Quintiere (2002), p. 3-162.</ref>

Free-plume relations should not simply be continued into this layer. Heskestad explicitly limits them at elevations where the plume enters smoke. A zone or ceiling-jet treatment is needed instead, depending on the required result.<ref name="Heskestad-2-1" />

Upper-layer smoke includes substantial entrained air as well as combustion products. Its temperature, volume and composition therefore reflect the whole plume history rather than only fuel chemistry. This influences smoke filling and the conditions at vents.<ref name="IFEG-2.5-2" /><ref name="VR-6.7" />

== Line plumes and boundary effects ==

A [[Line plume]] idealises a source distributed along a length rather than around a single central axis. Van Rossum discusses this geometry for smoke spilling from an adjacent space beneath a ceiling edge. That spill configuration entrains air differently from an isolated circular source, so a free axisymmetric plume relation cannot represent it without modification.<ref name="VR-6.7" />

Walls reduce the region from which air can be entrained. A plume immediately against a wall or in a corner therefore has different mass flow from a free plume. Simple half- or quarter-air approximations can illustrate the restriction, but the actual geometry and burner arrangement matter.<ref name="VR-6.7" />
[[File:fse-fire-plume-v2.svg|thumb|upright=1.5|alt=Free plume with all-side air and wall or corner plumes with restricted air paths.|Boundary position changes plume entrainment. Based on Van Rossum (2027), §6.7.]]

Van Rossum also describes the mirror-fire approach for particular wall and corner configurations. A wall-attached half-round burner can be represented as half of an equivalent full plume with doubled heat release, while a corner arrangement uses a corresponding fourfold source concept. These are model-specific constructions, not instructions for every fire.<ref name="VR-6.7" />

== Heat release and plume properties ==

Heat release rate drives plume buoyancy and energy transport. Heskestad divides total heat release into convective and radiative parts, with convective flux carried by the plume and radiation emitted in other directions. In the discussed sources, convective flux is rarely less than 60% to 70% of the total.<ref name="Heskestad-2-2" />

The often-used 70% convection and 30% radiation split is an approximation. Actual proportions vary with fuel, scale and combustion conditions, and the split becomes less reliable in developed compartment fires. A model should state the value used and its limitations.<ref name="VR-4.3">Van Rossum (2027), §4.3.</ref><ref name="VR-9.3">Van Rossum (2027), §9.3.</ref>

Combustion efficiency also affects the energy input. Theoretical complete-combustion power based on mass loss and heat of combustion can overestimate actual heat release when incomplete products remain. Heskestad cites efficiencies from near unity for some pools to substantially lower values for polystyrene and wood-pallet stacks.<ref name="Heskestad-2-2" />

Fire area and intensity influence both flame height and entrainment geometry. A small intense source and a larger distributed source with the same total power can produce different plume shapes and air entrainment. Total megawatts alone do not define the plume.<ref name="VR-4.6" /><ref name="Heskestad-2-3" />

Experimental evaluation can use collection hoods, temperature and velocity measurements, and observations of flame intermittency. Each technique addresses a different plume property. A flame-height observation should not be substituted for mass entrainment, and a centreline temperature should not be presented as the whole plume average.<ref name="Heskestad-2-2" />

Heskestad's mean flame height based on 50% intermittency illustrates the value of an explicit measurement definition. It reduces reliance on subjective selection of a visible edge, although it remains slightly lower than the human-eye average in the cited comparisons. The method and averaging basis should accompany the value.<ref name="Heskestad-2-2" />

Mass-flow measurements require a clear boundary as well. Zukoski's collection-hood approach described by Van Rossum balances exhaust extraction with plume flow entering a maintained smoke layer. That arrangement provides a different measurement from a point velocity reading within an unconfined plume.<ref name="VR-6.7" />

Model evaluation should then compare like with like. Source diameter, heat-release partition, virtual origin, measurement height and wall position can all change the result. Agreement in one configuration does not validate unrestricted use in another.<ref name="Heskestad-2-1" /><ref name="VR-6.7" />

A plume result should finally be checked against conservation and physical plausibility. Mass flow should be consistent with the chosen entrainment path and layer accumulation, while convective energy should remain consistent with the heat-release input. These checks can reveal an inappropriate model before its output is used for design.<ref name="Quintiere-3-163">Quintiere (2002), p. 3-163.</ref><ref name="IFEG-2.5-2" />

Plume models estimate smoke production and mass flow for smoke-management design. They support estimates of layer filling, vent flow and the dilution of combustion products. Their inputs must match the fire location and the height at which the result is needed.<ref name="IFEG-2.5-2" />

Detection analysis uses plume and ceiling-jet transport to estimate when heat or smoke reaches a device. Structural analysis uses the same flow to determine convective heating of ceilings and members. Radiative exposure requires a separate treatment rather than being inferred from convective plume power alone.<ref name="IFEG-2.5-2" /><ref name="VR-5.4">Van Rossum (2027), §5.4.</ref>

Zone models use the plume as a pump carrying mass from a lower zone to an upper zone. Quintiere notes that many such models neglect plume volume and transport time relative to the layers. These assumptions simplify the equations but can matter in large spaces or rapidly changing fires.<ref name="Quintiere-3-163" />

Stationary models evaluate plume properties at a selected time, while dynamic models update them as heat release changes. A stationary choice can be conservative in some assessments, but it does not show the sequence by which those conditions were reached.<ref name="VR-9.3" />

== Limits and uncertainty ==

A plume is not a fixed chimney of combustion products. Its boundary, temperature and composition fluctuate with turbulence, source behaviour and surroundings. Time-averaged properties should be identified as such rather than interpreted as instantaneous uniform values.<ref name="Heskestad-2-1" />

Free-plume assumptions fail or need modification near walls, ceilings, smoke layers and obstructions. Different models address different configurations, and choosing one by name alone is not enough. Geometry and application range must be checked.<ref name="Heskestad-2-1" /><ref name="VR-6.7" />

Dilution does not necessarily make smoke harmless. Entrained air lowers concentration and temperature but increases total mass flow, so substantial energy and combustion products can still be transported. Hazard depends on the resulting conditions and exposure time at the receiver.<ref name="VR-5.3" /><ref name="IFEG-2.5-2" />

Height is another required reference. Plume properties above a fuel surface, at mean flame height and at the underside of a smoke layer describe different stages of transport. Reporting only a vertical distance without its reference point can make otherwise correct model results impossible to compare.<ref name="Heskestad-2-2" /><ref name="VR-6.7" />

== See also ==

* [[Convection]]
* [[Fire dynamics]]
* [[Diffusion flame]]
* [[Smoke filling]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002). Compartment fire modeling. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Fire Dynamics]]

Fire load

2026-11-02T17:57:39Z

Thomas: Improve Fire load: sourced explanations, calculations and internal links (Codex)

'''Fire load''' is the total chemical energy that would be released if all combustible material in a defined place burned completely. It is commonly expressed in megajoules and can also be related to floor area as fire-load density. The quantity describes potential energy, not the heat release rate at a particular moment.<ref name="VR-4.4">Van Rossum (2027), §4.4.</ref><ref name="IFEG-2.4-2">Australian Building Codes Board et al. (2005), pp. 2.4-2–2.4-3.</ref>

Fire load includes the energy content of the fuel inventory rather than only its mass or volume. Materials with different heats of combustion can therefore produce very different fire loads from the same mass. The physical arrangement and combustion conditions later determine how much of that potential energy is actually released and at what rate.<ref name="Drysdale-1-92">Drysdale (2002), p. 1-92.</ref><ref name="VR-4.5">Van Rossum (2027), §4.5.</ref>

This makes fire load useful for estimating possible fire duration, total thermal exposure and design-fire context. It does not by itself predict ignition, flame spread, peak power or the temperature history of a compartment.<ref name="IFEG-2.4-2" /><ref name="Cadorin-Franssen-396">Cadorin and Franssen (2003), p. 396.</ref>

== Energy content and inventory ==

A fire-load assessment begins by identifying combustible materials and their quantities. Mass, volume or item count can be converted into energy using an appropriate calorific value. Every material needs its own basis, because a table can express energy per kilogram, per item or per square metre.<ref name="VR-4.4" />

[[Heat of combustion]] is the heat released by complete oxidation of a unit quantity of fuel to stable end products. Net heat of combustion treats product water as vapour and is identified by Drysdale as the value to use in fire calculations. Its measurement basis and initial conditions must accompany the data.<ref name="Drysdale-1-93">Drysdale (2002), p. 1-93.</ref>

Values illustrate the range between materials. Drysdale's table lists propane at 46.45 kJ/g, cellulose at 16.09 kJ/g and polyethylene at 43.28 kJ/g. Equal masses therefore do not represent equal chemical energy, and actual fires can release less than these complete-oxidation values.<ref name="Drysdale-1-93" /><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

Van Rossum gives object-based examples including 1,884 MJ for a three-seat sofa and 6,000 to 12,000 MJ for a car. He also lists beech wood at 18 MJ/kg and diesel oil at 42 MJ/kg. These examples are source values for inventory, not measurements of heat release rate or fire severity in a particular room.<ref name="VR-4.4" />
[[File:fse-fire-load-v3.svg|thumb|upright=1.5|alt=Sofa 1,884 MJ and car energy range 6,000 to 12,000 MJ.|Example chemical energy contents of a sofa and a car. Based on Van Rossum (2027), §4.4.]]

== Variable and permanent fire load ==

Variable fire load consists of combustible contents and furnishings that can change with building use. Furniture, stored goods and other inventory fall into this group. Their quantity and arrangement can vary over the life of a compartment.<ref name="VR-4.4" />

Permanent fire load consists of combustible construction components. It is associated with the building itself rather than its changing contents. Timber elements and combustible finishes can therefore require a separate inventory from furniture and stored products.<ref name="VR-4.4" />

The distinction improves traceability but does not imply different combustion chemistry. Both groups contribute potential energy, and both need material-specific calorific values. Their treatment in a design fire can differ because contents and construction ignite and burn in different arrangements.<ref name="VR-4.4" /><ref name="IFEG-2.4-2" />
[[File:fse-fire-load-v1.svg|thumb|upright=1.5|alt=Room contents and construction separated into variable and permanent fire-load groups.|Variable and permanent contributions to fire load. Based on Van Rossum (2027), §4.4.]]

A complete inventory identifies what is included and excluded. Omitting concealed materials, linings or protected contents can change the estimate, while counting the same object as both contents and construction double-counts it. The system boundary should match the fire scenario.<ref name="IFEG-2.4-2" />

== Fire-load density ==

[[Fire load density]] relates energy to a reference area, commonly the internal floor area of a compartment. It is often expressed in megajoules per square metre. This normalisation supports comparison between compartments and provides an input to some structural and parametric fire methods.<ref name="IFEG-2.4-2" /><ref name="Cadorin-Franssen-396" />

Density is not a substitute for total energy. A small compartment with high density can contain less total energy than a large compartment with lower density. The required output determines whether total fire load, density or both should be reported.<ref name="IFEG-2.4-2" />
[[File:fse-fire-load-v2.svg|thumb|upright=1.5|alt=Two rooms with different areas illustrating total energy and energy per square metre.|Total fire load and fire-load density answer different questions. Based on Australian Building Codes Board et al. (2005), pp. 2.4-2–2.4-3.]]

The reference area must be consistent. Floor area, internal surface area and burning area answer different questions. Fire-load density per floor area should not be combined with heat release rate per unit burning area as though they were the same quantity.<ref name="VR-4.6">Van Rossum (2027), §4.6.</ref><ref name="IFEG-2.4-2" />

Van Rossum gives example densities of 750 to 1,000 MJ/m² for an assembly occupancy, 1,800 MJ/m² for a library and 950 MJ/m² for a residential occupancy in his source table. These values belong to the cited method and occupancy descriptions and should not replace a project-specific inventory where one is required.<ref name="VR-4.4" />

== Moisture, protection and incomplete combustion ==

Moisture changes effective energy content because heat is required to evaporate water. Van Rossum notes that some values already relate to equilibrium moisture or are tabulated as net values with this correction included. Applying another correction without checking the basis can subtract the energy twice.<ref name="VR-4.4" /><ref name="IFEG-2.4-2" />

Protected contents may not burn completely. Combustible material inside a steel cabinet or other fire-resistant container can have a lower effective fire load than the same material in the open. The reduction depends on fire temperature and duration, container integrity and the nature of the contents.<ref name="IFEG-2.4-2" />

The 2005 guidelines caution that these effects are difficult to quantify unless the container has been tested for fire resistance. Assuming full protection or zero contribution without such evidence would be unsupported. The protected and unprotected inventories should be distinguished in the assessment.<ref name="IFEG-2.4-2" />

Incomplete combustion also means that total theoretical energy is rarely all released in a real fire. Partially oxidised products and unburnt material retain chemical energy. Combustion efficiency changes with material and conditions, so actual energy release must be evaluated separately from the inventory.<ref name="Drysdale-1-95" /><ref name="Heskestad-2-2">Heskestad (2002), p. 2-2.</ref>

== Fire load and heat release rate ==

[[Heat release rate]] is the power produced by combustion at a particular time. Fire load is energy available over the whole scenario. Power integrated over time gives energy released, but a constant power cannot be assumed without a justified design-fire model.<ref name="VR-4.5" /><ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref>

A high fire load can coexist with low power when the fuel is difficult to decompose or oxygen is limited. A small fuel package can also produce high power briefly before being depleted. Peak heat release rate and total energy must therefore be assessed independently.<ref name="VR-4.4" /><ref name="VR-4.8">Van Rossum (2027), §4.8.</ref>

Mass loss rate provides one link between them, but effective heat of combustion can vary during a test. Babrauskas demonstrates this with cedar, where the effective value changed substantially between early burning and charring. A constant conversion is not always valid.<ref name="Babrauskas-3-1" />

Fire duration can be estimated by dividing energy release by an assumed heat release rate only when that rate is suitably defined. Ventilation-controlled fires can extend burning beyond a simple fuel-controlled estimate, while suppression can shorten it. Any duration result therefore depends on the selected combustion model.<ref name="VR-4.8" /><ref name="Cadorin-Franssen-400">Cadorin and Franssen (2003), pp. 400–401.</ref>

== Use in design fires ==

A [[Design fire]] needs both an energy-related context and a time-dependent description. Fire load informs what fuel is present and how long it might support burning, while a heat-release curve specifies how combustion develops. Using only one of these leaves part of the scenario undefined.<ref name="IFEG-1.2-29">Australian Building Codes Board et al. (2005), pp. 1.2-29–1.2-30.</ref><ref name="IFEG-2.4-2" />

Fire-load density can support the choice of design parameters in structural and compartment models. Cadorin and Franssen define characteristic and design fire-load densities as inputs to OZone, with the heat release rate treated separately. This illustrates the different roles of energy inventory and power in one model.<ref name="Cadorin-Franssen-396" />

Spatial arrangement also matters. Fuel distributed among several objects can ignite sequentially, producing a different curve from the same total mass arranged as one package. Protected, fixed and transient inventories should therefore be located as well as counted.<ref name="IFEG-2.6-12">Australian Building Codes Board et al. (2005), p. 2.6-12.</ref>

Surveys of similar buildings can provide statistical fire-load densities when direct inventory is impractical. The 2005 guidelines recommend comparable use and size, sufficient buildings to address variability and, preferably, similar social and economic conditions. Published data still require appropriate sampling and evaluation.<ref name="IFEG-2.4-3">Australian Building Codes Board et al. (2005), p. 2.4-3.</ref>

These exposure methods should be reviewed against the inventory boundary. An equivalent duration based on all theoretical fuel energy can overstate what is available if protected contents do not burn, while an incomplete inventory can understate it. The calculation should show which material contributions and combustion efficiencies were accepted.<ref name="IFEG-2.4-2" /><ref name="Drysdale-1-95" />

Ventilation can alter both the rate and location of energy release. Oxygen-limited compartments can release unburnt volatiles that burn outside, shifting some thermal exposure away from the original fire load inventory. A duration or equivalence calculation must state whether it includes that external combustion.<ref name="VR-4.8" /><ref name="Drysdale-1-95" />

The inventory can also change during a project or building lifecycle. Transient storage, new furnishings and alterations to combustible construction can invalidate an earlier total. A fire-load assessment should therefore identify its date and intended operating condition rather than being treated as a permanent property of the room.<ref name="IFEG-2.4-3" /><ref name="VR-4.4" />

Review by another analyst is easier when each conversion and assumption remains visible. The source of every calorific value, the treatment of moisture, the protected-fuel allowance and the reference area should be reproducible. This allows uncertainty in the inventory to be carried into later fire-duration and structural calculations.<ref name="IFEG-2.4-2" /><ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

[[Time equivalence]] relates the thermal effect of a real or parametric fire to an equivalent exposure under a standard fire curve. Fire load helps determine the energy available for that comparison, but it does not define the equivalence alone. Ventilation, boundaries and heat-release history also shape thermal severity.<ref name="Cadorin-Franssen-396" /><ref name="VR-4.4" />

A [[Parametric fire curve]] represents gas temperature against time using compartment and fire parameters. Fire-load density can be one of those inputs, alongside openings and boundary properties. The resulting curve differs from a simple total-energy calculation because it describes how the environment changes.<ref name="Cadorin-Franssen-395">Cadorin and Franssen (2003), pp. 395–396.</ref>

These methods are used in structural fire engineering to estimate member exposure and fire resistance. The total energy affects potential duration, while the curve determines heating rate and peak conditions. A high fire load can therefore be consistent with different structural exposures.<ref name="Cadorin-Franssen-429">Cadorin et al. (2003), pp. 429–430.</ref>

Model scope remains important. Parametric and zone approaches make assumptions about compartment shape, combustion and ventilation. Applying them outside those conditions can produce a temperature history that looks precise but lacks a valid physical basis.<ref name="VR-9.2">Van Rossum (2027), §9.2.</ref><ref name="Cadorin-Franssen-395" />

== Inventory methods and worked interpretation ==

A transparent inventory uses a table of material, quantity, calorific value and resulting energy. Values with different units are converted before being summed, and permanent and variable contributions are identified. The final total is then related to a clearly stated reference area if density is needed.<ref name="VR-4.4" /><ref name="IFEG-2.4-2" />

Van Rossum's warehouse example uses a storage volume of 3,500 m³, an effective storage density of 135 kg/m³ and a calorific value of 23 MJ/kg. These inputs describe the stored inventory. The calculation below follows their conversion into energy and wood-equivalent mass.<ref name="VR-4.4" />

Wood-equivalent units provide another way to express energy, but they do not mean that the actual inventory is wood. The conversion basis must be stated, and normal SI energy units remain clearer for subsequent heat-release and duration calculations.<ref name="VR-4.4" />

=== Calculating the inventory ===

For several materials, each mass is multiplied by its net heat of combustion and the resulting energies are added. A volume-based inventory first converts stored volume to mass using the appropriate bulk density. Fire-load density then divides the total energy by the selected floor area.<ref name="VR-4.4" /><ref name="IFEG-2.4-2" />
<math display="block">E=\sum_i m_i H_i,\qquad m=\rho_b V,\qquad q_f=\frac{E}{A_f}</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>E</math> || Total potential chemical energy || MJ
|-
| <math>m_i</math> || Mass of material i || kg
|-
| <math>H_i</math> || Net heat of combustion of material i || MJ/kg
|-
| <math>\rho_b</math> || Bulk density of the stored inventory || kg/m³
|-
| <math>V</math> || Occupied storage volume || m³
|-
| <math>A_f</math> || Reference floor area || m²
|-
| <math>q_f</math> || Fire-load density || MJ/m²
|}

Using the warehouse quantities above, the fuel mass is 3,500 × 135 = 472,500 kg. Multiplication by 23 MJ/kg gives 10,867,500 MJ, or approximately 1.09 × 10<sup>7</sup> MJ. Dividing by the reference wood value of 19 MJ/kg gives about 5.72 × 10<sup>5</sup> kg of wood equivalent.<ref name="VR-4.4" />

Bulk density includes the way the inventory occupies its storage volume. Substituting a solid material density for the stated storage density would describe a different inventory. Equally, the storage volume is not a floor area: a fire-load density cannot be obtained from this example without a separate area input.<ref name="VR-4.4" /><ref name="IFEG-2.4-2" />

This arithmetic represents complete combustion of the included fuel. It does not decide whether protected material becomes involved or whether all chemical energy is released inside the compartment. Those changes belong to the fire scenario and combustion model, rather than to an unexplained alteration of the calorific value.<ref name="Drysdale-1-95" /><ref name="IFEG-2.4-2" />

== Limits and common misunderstandings ==

Fire load is not the mass of combustible material. Mass must be combined with energy content, and different units require conversion. Two inventories with the same mass can contain different chemical energy.<ref name="Drysdale-1-93" />

It is also not heat release rate per unit area. Fire-load density concerns energy over a reference area, while heat-release intensity concerns power over a defined burning area. Similar unit forms do not make the concepts interchangeable.<ref name="VR-4.6" /><ref name="IFEG-2.4-2" />

Total theoretical energy is not a prediction of energy actually released. Moisture, incomplete combustion, container protection and suppression can reduce it, and external burning can change where it is released. The scenario boundary must be stated.<ref name="Drysdale-1-95" /><ref name="IFEG-2.4-2" />

a larger fire load does not guarantee a higher peak temperature or faster evacuation risk. Ignition, heat release rate, spread, ventilation and occupant response determine those outcomes. Fire load is one part of the wider fire-dynamics description.<ref name="VR-4.5" /><ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref>

Where the total drives a safety decision, alternative inventories can show its influence. Variable contents, moisture and protected fractions can be varied within defensible ranges rather than assigned false certainty. The resulting change in duration or exposure reveals whether a more detailed survey is needed.<ref name="IFEG-2.4-3" /><ref name="VR-1.7" />

== See also ==

* [[Fire dynamics]]
* [[Combustibility]]
* [[Mass timber]]
* [[Sprinkler hazard classification]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Cadorin, J.-F., Pintea, D., Dotreppe, J.-C., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 2: Methodology and application. ''Fire Safety Journal, 38'', 429–451.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Fire Dynamics]]

Fire dynamics

2026-11-02T17:56:07Z

Thomas: Improve Fire dynamics: sourced explanations, calculations and internal links (Codex)

'''Fire dynamics''' is the study of how fires start, develop, move and decline through interactions between fuel, combustion, heat transfer and fluid flow. It connects material response with flames, plumes, smoke and enclosure conditions. The resulting fire behaviour is time-dependent and cannot usually be inferred from fuel quantity or ignition source alone.<ref name="VR-1.6">Van Rossum (2027), §1.6.</ref><ref name="Heskestad-2-1">Heskestad (2002), p. 2-1.</ref>

The subject links chemical energy release with physical transport. Combustion produces heat and products, buoyancy moves hot gases, and heat transfer changes both the original fuel and surrounding objects. These feedbacks can accelerate growth, restrict it or lead to extinction.<ref name="Drysdale-1-90">Drysdale (2002), p. 1-90.</ref><ref name="VR-4.3">Van Rossum (2027), §4.3.</ref>
[[File:fse-fire-dynamics-v1.svg|thumb|upright=1.5|alt=Feedback among heat release, fuel decomposition, heat transfer and plume flow.|Fire dynamics is a coupled feedback system. Based on Van Rossum (2027), §4.3 and Heskestad (2002), p. 2-1.]]

Fire dynamics supports design-fire selection, smoke and structural analysis, detection, suppression and evacuation assessment. Each application needs a defined scenario and timescale, with material data and boundary conditions that match the building or object being studied.<ref name="IFEG-2.4-4">Australian Building Codes Board et al. (2005), p. 2.4-4.</ref><ref name="IFEG-2.5-2">Australian Building Codes Board et al. (2005), p. 2.5-2.</ref>

== Fuel, energy and heat release ==

Fuel contains chemical energy, but this energy is not released instantly or completely in every fire. Solids often require pyrolysis, liquids require evaporation and the resulting gases must mix with oxygen. Decomposition and burning rates therefore connect the fuel inventory with observable fire development.<ref name="VR-3.1">Van Rossum (2027), §3.1.</ref><ref name="VR-4.1">Van Rossum (2027), §4.1.</ref>

[[Fire load]] describes the chemical energy potentially available from combustible material. It differs from [[Heat release rate]], which describes the power produced by combustion at a particular time. A large fire load can coexist with low heat release rate when decomposition or oxygen supply is limited.<ref name="VR-4.4">Van Rossum (2027), §4.4.</ref><ref name="VR-4.5">Van Rossum (2027), §4.5.</ref>

Heat release rate is commonly expressed in kilowatts or megawatts. It is related to mass loss rate and effective heat of combustion, but that relationship need not remain constant as a material moves through different burning stages. Effective heat of combustion and combustion efficiency can vary with fuel and conditions.<ref name="Babrauskas-3-1">Babrauskas (2002), p. 3-1.</ref><ref name="Heskestad-2-2">Heskestad (2002), p. 2-2.</ref>

A [[Design fire]] simplifies this behaviour for a particular engineering assessment. It may specify heat release rate against time, fire area, combustion products or other inputs. The simplification is intended to represent selected scenarios, not to reproduce every natural fire.<ref name="IFEG-1.2-29">Australian Building Codes Board et al. (2005), pp. 1.2-29–1.2-30.</ref>

== Heat transfer and feedback ==

[[Heat transfer]] links the fire with its fuel and surroundings. Radiation and convection heat new material, while conduction moves energy into solids. The heated material then evaporates or decomposes, supplying additional gaseous fuel to the fire.<ref name="VR-5.1">Van Rossum (2027), §5.1.</ref><ref name="Beyler-Hirschler-1-110">Beyler and Hirschler (2002), p. 1-110.</ref>

This feedback determines whether a fire sustains itself. Heat production must exceed losses sufficiently to maintain reaction and fuel production. When losses dominate, ignition can fail or an existing flame can extinguish even though fuel and oxygen remain.<ref name="Drysdale-1-97">Drysdale (2002), p. 1-97.</ref>

Orientation and geometry change the feedback. Upward flame spread can preheat fuel above the burning region, while enclosed spaces retain energy in hot gases and surfaces. These arrangements can accelerate growth without any change in the fuel's basic chemical composition.<ref name="VR-4.3" />

Fire growth also changes the exposure itself. More burning area can increase heat release rate, which then increases radiation, plume flow and heating of neighbouring targets. Spread and heat release therefore develop together rather than as independent calculations.<ref name="Quintiere-2-246">Quintiere (2002b), p. 2-246.</ref>

=== Following the released energy ===

The distinction between total fire power and its destination is central to an energy balance. For a simplified freely burning source, escaping energy can be divided into convective and radiative parts. Heskestad also notes that porous fuel arrangements may retain some energy during burning, so this split is an approximation to the chosen system boundary.<ref name="Heskestad-2-2" />

If energy storage in the source is neglected, the two fractions add to the total heat release rate. The radiative fraction specifies the proportion leaving as radiation; the remainder is assigned to the convective flow.<ref name="Heskestad-2-2" />
<math display="block">\dot Q=\dot Q_c+\dot Q_r,\qquad \dot Q_r=\chi_r\dot Q,\qquad \dot Q_c=(1-\chi_r)\dot Q</math>

{| class="wikitable"
! Symbol !! Description !! Unit
|-
| <math>\dot Q</math> || Total heat release rate || kW
|-
| <math>\dot Q_c</math> || Convective heat release rate || kW
|-
| <math>\dot Q_r</math> || Radiative heat release rate || kW
|-
| <math>\chi_r</math> || Radiative fraction || dimensionless
|}

For the 1 MW source used in Van Rossum's fire-area example, a 70% convective and 30% radiative split gives 700 kW and 300 kW respectively. These are alternative destinations for the same released power. Adding the convective portion to the full 1 MW would count that energy twice.<ref name="VR-4.3" /><ref name="VR-4.6">Van Rossum (2027), §4.6.</ref>

The 700 kW is an input to the rising flow, not a prediction that this much heat remains stored in the upper layer. Hot gases can leave through openings, and heat transfers to the compartment boundaries. A layer-temperature calculation therefore needs mass transport and heat losses as well as the source power.<ref name="Quintiere-3-163">Quintiere (2002a), p. 3-163.</ref><ref name="VR-9.3">Van Rossum (2027), §9.3.</ref>

The split also does not specify the radiation reaching a particular object. Distance, orientation, intervening smoke and the emitting region affect that exposure. Van Rossum cautions against carrying the simple pre-flashover division unchanged into a fully developed compartment fire, where hot boundaries and gases exchange radiation throughout the enclosure.<ref name="VR-5.4">Van Rossum (2027), §5.4.</ref><ref name="VR-9.3" />

== Plumes, entrainment and smoke ==

A [[Fire plume]] is the buoyant flow of hot gases and any flames above a combustion region. It entrains surrounding air through turbulence, increasing mass flow while diluting temperature and combustion-product concentration. The plume transports energy and smoke upwards.<ref name="Heskestad-2-1" /><ref name="VR-6.7">Van Rossum (2027), §6.7.</ref>

Entrained air can greatly exceed the mass flow of burned fuel. This makes plume mass flow and smoke production dependent on fire-driven mixing as well as on fuel consumption. Plume models estimate this transport for detection, smoke filling, venting and structural heating.<ref name="IFEG-2.5-2" /><ref name="Heskestad-2-1" />

The plume changes with height. Heskestad describes centreline temperatures that can remain comparatively steady in the lower flame and then decay in the intermittent region, while velocities reach a maximum and subsequently decline. Mean flame height separates much of the reacting region from the overlying inert plume.<ref name="Heskestad-2-2" />

Walls, corners and ceilings alter the flow. They restrict entrainment and redirect hot gases, so an axisymmetric free-plume model does not apply unchanged. When the plume enters a smoke layer, Heskestad cautions that the free-plume relations cease to be valid.<ref name="Heskestad-2-1" /><ref name="VR-6.7" />

== Compartment fire development ==

A [[Compartment fire]] adds boundaries, openings and accumulating hot gases to the fire system. A plume can feed a hot upper layer above a cooler lower layer, producing thermal stratification. Conservation of mass and energy then connects the fire, layers, vents and wall losses.<ref name="Quintiere-3-162">Quintiere (2002a), p. 3-162.</ref><ref name="Cadorin-Franssen-399">Cadorin and Franssen (2003), pp. 399–400.</ref>

Early development is commonly fuel controlled because sufficient oxygen is available and fire size depends on fuel-gas production. Later, limited openings can make oxygen availability controlling. Unburnt pyrolysis gases may then leave the compartment and burn outside after mixing with fresh air.<ref name="VR-4.8">Van Rossum (2027), §4.8.</ref><ref name="Drysdale-1-95">Drysdale (2002), p. 1-95.</ref>

[[Flashover]] marks a rapid transition towards involvement of combustible materials throughout the compartment. Radiation from the hot upper layer and heated boundaries can drive this transition. It changes the relevance of local-fire assumptions and can produce external flaming and much higher boundary exposure.<ref name="VR-4.7">Van Rossum (2027), §4.7.</ref><ref name="Cadorin-Franssen-412">Cadorin and Franssen (2003), p. 412.</ref>

Zone models represent pre-flashover conditions with uniform upper and lower gas layers and fully developed conditions with one mixed zone. These are modelling approximations. Real temperatures and compositions vary through the space, and strong mixing or unusual geometry can invalidate the assumed structure.<ref name="Quintiere-3-162" /><ref name="VR-9.1">Van Rossum (2027), §9.1.</ref>
[[File:fse-fire-dynamics-v3.svg|thumb|upright=1.5|alt=Hot upper and cool lower zones changing into one mixed compartment zone.|Zone models simplify stratified and mixed compartment states. Based on Quintiere (2002a), p. 3-162 and Cadorin and Franssen (2003), pp. 399–400.]]

== Growth, steady burning and decay ==

Fire development is often divided into growth, fully developed burning and decay. The growth stage includes ignition and increasing involvement of fuel, while the developed stage can be limited by fuel production or ventilation. Decay can follow fuel depletion or suppression.<ref name="VR-4.11">Van Rossum (2027), §4.11.</ref>
[[File:fse-fire-dynamics-v2.svg|thumb|upright=1.5|alt=Timeline of growth, developed fire and decay with an early-extinction branch.|Common fire stages and an alternative early-exit path. Based on Van Rossum (2027), §4.11.]]

These stages are not mandatory or equal in duration. A small fire can extinguish before flashover, an active system can interrupt growth, and smouldering can persist without a visible developed-flame stage. The design description should include only stages supported by the scenario.<ref name="VR-4.11" /><ref name="IFEG-1.2-29" />

Simplified design curves sometimes use quadratic growth followed by steady heat release and a selected decay. Such curves are useful for comparing scenarios but can hide incubation, changing combustion efficiency and object-to-object spread. Their assumptions need to be documented.<ref name="IFEG-1.2-29" /><ref name="IFEG-2.4-11">Australian Building Codes Board et al. (2005), p. 2.4-11.</ref>

Decay does not immediately remove every hazard. Hot surfaces and fuel beds can retain energy, and smouldering can continue after visible flaming declines. Heat transfer and oxygen readmission can still produce delayed ignition or reignition.<ref name="Ohlemiller-2-206">Ohlemiller (2002), p. 2-206.</ref><ref name="Rockett-Milke-1-29">Rockett and Milke (2002), p. 1-29.</ref>

== Models and measurements ==

Fire-dynamics models range from simple hand calculations to zone and field models. A suitable model represents the controlling fuel, flow and heat-transfer mechanisms without demanding more detail than the available data support. More equations do not remove uncertainty in the scenario.<ref name="VR-8.1">Van Rossum (2027), §8.1.</ref><ref name="Quintiere-3-162" />

Heat-release measurements provide a basis for many models. Open-burning calorimetry measures an item without a surrounding room, while room tests include enclosure feedback. Bench-scale tests offer material response data, but full-scale fire behaviour still depends on object geometry and installation.<ref name="Babrauskas-3-1" /><ref name="Babrauskas-3-3">Babrauskas (2002), p. 3-3.</ref>

Room effects are fuel- and configuration-specific. Babrauskas reports limited effects for some upholstered chairs at lower heat release rates but much stronger effects for mattresses and liquid pools. No single correction can be applied to every product.<ref name="Babrauskas-3-2">Babrauskas (2002), p. 3-2.</ref>

Validation compares predictions with experiments or incident evidence. A mismatch can arise from source description, material properties, plume choice, boundary losses or ignition timing. Checking only numerical implementation would miss these modelling assumptions.<ref name="Cadorin-Franssen-395">Cadorin and Franssen (2003), pp. 395–396.</ref><ref name="VR-9.2">Van Rossum (2027), §9.2.</ref>

== Applications and uncertainty ==

Detection and suppression analysis uses fire dynamics to estimate when heat and combustion products reach devices. Smoke analysis uses plume and layer transport, while structural analysis uses time-dependent thermal exposure. Evacuation analysis then compares changing conditions with the time people need to respond and move.<ref name="IFEG-2.5-2" /><ref name="IFEG-1.6-3">Australian Building Codes Board et al. (2005), p. 1.6-3.</ref>

Each application can require a different design fire. A detector study may focus on early growth, a structural study on developed exposure and a smoke-control study on plume entrainment and venting. One heat-release curve should not be reused without checking these different sensitivities.<ref name="IFEG-1.2-29" /><ref name="Babrauskas-3-3" />

Uncertainty includes both input variability and model limitations. Fuel arrangement, ignition source, ventilation and material properties can change between apparently similar scenarios. Zone uniformity and simplified plume relationships add further approximation.<ref name="Quintiere-3-162" /><ref name="VR-9.2" />

Sensitivity analysis can show which assumptions control the result. Heat release rate, fire area, growth rate, opening size and heat-transfer properties are common candidates. Results should be rounded with this uncertainty in mind rather than presented with unsupported precision.<ref name="VR-1.7">Van Rossum (2027), §1.7.</ref>

== Limits and common misunderstandings ==

Fire dynamics is not simply the chemistry of combustion. Thermochemistry describes energy changes but does not determine reaction rate, mixing or heat transfer. Fire behaviour emerges from all of these together.<ref name="Drysdale-1-90" />

A larger fuel inventory does not automatically mean a larger current fire. Oxygen access, exposed area, decomposition and heat losses can keep heat release rate low. Fire load and heat release rate must remain distinct.<ref name="VR-4.4" /><ref name="VR-4.5" />

A visible flame is not the whole fire. Hot gases, smoke, smouldering and heated boundaries can continue to affect people and structures. Evaluating only the flame region misses these pathways.<ref name="Ohlemiller-2-200">Ohlemiller (2002), p. 2-200.</ref><ref name="VR-5.1" />

a model is not the fire itself. It is a selected representation whose useful output depends on applicable geometry, data and assumptions. Fire-dynamics knowledge includes deciding when those assumptions no longer hold.<ref name="Quintiere-3-162" /><ref name="VR-9.2" />

A scenario record should begin with the initiating event and fuel arrangement. It should identify the first item, nearby targets, enclosure and openings, then state which combustion and spread modes are expected. This prevents a design fire from being selected independently of the physical situation it represents.<ref name="IFEG-2.4-4" /><ref name="IFEG-1.2-29" />

The time basis needs equal clarity. Ignition, detection, flashover, barrier failure and fuel depletion can occur at different stages, and some may never occur. A result reported only as a single peak condition cannot show which of these transitions has been included.<ref name="VR-4.11" /><ref name="IFEG-1.6-3" />

Mass and energy balances provide a useful consistency check. Fuel input, air entrainment, vent flow and accumulation should remain compatible with the selected zone structure. Energy should likewise be assigned to gas heating, boundaries, radiation and losses without being counted twice.<ref name="Quintiere-3-163" />

Spatial assumptions should be tested against the enclosure. A uniform layer can hide temperature differences between plume and room edges, while simultaneous burning of a large floor can overstate early severity. Alternative zone or grid descriptions may be needed when those differences control the decision.<ref name="VR-9.2" /><ref name="IFEG-2.6-12">Australian Building Codes Board et al. (2005), p. 2.6-12.</ref>

Data from other fires require the same scrutiny. Object geometry, ignition method and test enclosure can alter heat release and spread, so an apparently similar item name is not sufficient. The analysis should explain why the selected evidence is applicable.<ref name="Babrauskas-3-3" />

The choice between stationary and dynamic treatment follows the decision being made. A stationary model evaluates selected conditions, while a dynamic model updates them as the fire changes. The first can support a simple comparison, but only the second shows how the fire reached those conditions and when thresholds were crossed.<ref name="VR-9.3" />

Model scope should also remain proportionate to the evidence. A zone model may represent average layer behaviour with limited input, whereas a more detailed flow model demands more geometry and boundary data. Additional detail is useful only when those inputs and the underlying physical assumptions remain defensible.<ref name="Quintiere-3-162" /><ref name="VR-9.2" />

Time histories allow several performance questions to be examined in one scenario. Detection can be assessed during early growth, tenability during smoke accumulation and structural exposure during developed burning. Selecting a different time for each is clearer than forcing one peak fire state to represent all of them.<ref name="IFEG-2.5-2" /><ref name="IFEG-2.6-2">Australian Building Codes Board et al. (2005), p. 2.6-2.</ref>

This time-based approach also exposes assumptions that a peak-only comparison would hide. Early open conditions can give way to ventilation limitation, while local stratification can become more uniform. A model should be reviewed whenever the fire moves into a regime for which its original assumptions were not intended.<ref name="VR-4.8" /><ref name="VR-9.1" />

A scenario comparison should change one relevant assumption at a time where possible. This makes the influence of ventilation, fuel arrangement or growth rate visible and helps distinguish a well-supported conclusion from one controlled by a single uncertain choice. The final report can then explain both the result and its sensitivity.<ref name="VR-1.7" />

== See also ==

* [[Fire investigation]]
* [[Combustion]]
* [[Thermal radiation]]

== Notes ==

<references />

== References ==

* Australian Building Codes Board, National Research Council of Canada, International Code Council, & Department of Building and Housing New Zealand. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Babrauskas, V. (2002). Heat release rates. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Beyler, C. L., & Hirschler, M. M. (2002). Thermal decomposition of polymers. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Cadorin, J.-F., & Franssen, J.-M. (2003). A tool to design steel elements submitted to compartment fires: OZone V2. Part 1: Pre- and post-flashover compartment fire model. ''Fire Safety Journal, 38'', 395–427.
* Drysdale, D. D. (2002). Thermochemistry. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Heskestad, G. (2002). Fire plumes, flame height, and air entrainment. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Ohlemiller, T. J. (2002). Smoldering combustion. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002a). Compartment fire modeling. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Quintiere, J. G. (2002b). Surface flame spread. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Rockett, J. A., & Milke, J. A. (2002). Conduction of heat in solids. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Van Rossum, E. (2027). ''Introduction to Fire Safety Engineering''. Fire Safety Academy.

[[Category:Fire Dynamics]]

Category:Structural Fire Engineering

2026-11-02T15:14:31Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Structural fire engineering''' covers the response of load-bearing structures to fire exposure. Articles connect the fire environment, heat transfer into structural members and the resulting changes in material behaviour, deformation and load-bearing performance.

Topics include [[Fire resistance|fire resistance]], [[Steel in fire|steel]], [[Concrete in fire|concrete]] and [[Timber in fire|timber]], together with charring, spalling and thermal expansion. The category also covers [[Parametric fire curve|fire exposure curves]], calculation methods, restraint and the response of structural systems. It links the assessment of individual members with wider questions of structural stability and the progression of damage during a fire.

'''Related categories:''' [[:Category:Physics & Heat Transfer|Physics & Heat Transfer]] · [[:Category:Materials & Fire Testing|Materials & Fire Testing]] · [[:Category:Passive Fire Protection|Passive Fire Protection]]

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Category:Special Hazards & Building Types

2026-11-02T15:14:25Z

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'''Special hazards and building types''' brings together articles on fire situations shaped by particular technologies, fuels, building forms or surroundings. Topics include [[Lithium-ion battery fire|lithium-ion battery fires]], thermal runaway, [[Electric vehicle fire|electric vehicle fires]], [[High-rise building|high-rise buildings]], warehouses and tunnels.

The category also covers car parks, facade fires, [[Wildfire|wildfires]] and the [[Wildland-urban interface|wildland–urban interface]]. These articles apply fire science and engineering concepts to specific contexts, considering the influence of geometry, fuel arrangements, access and occupant movement. They provide routes into the broader categories concerned with fire development, protection, evacuation and risk analysis.

'''Related categories:''' [[:Category:Enclosure Fires|Enclosure Fires]] · [[:Category:Fire Risk Analysis|Fire Risk Analysis]] · [[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]

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Category:Smoke, Toxicity & Tenability

2026-11-02T15:14:19Z

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'''Smoke, toxicity and tenability''' covers the fire products and exposure conditions considered when assessing the effects of fire on people. It includes [[Smoke|smoke]], soot, [[Carbon monoxide|carbon monoxide]], other combustion gases and [[Fire toxicity|fire toxicity]].

Articles examine [[Visibility in smoke|visibility in smoke]], exposure to heat, oxygen depletion and methods for describing the effects of toxic gases. [[Tenability criteria|Tenability criteria]] connect these conditions with the assessment of whether an environment remains compatible with escape or another specified activity. The category links the production and concentration of fire products with the interpretation of exposure and occupant safety assessments.

'''Related categories:''' [[:Category:Combustion|Combustion]] · [[:Category:Smoke Control|Smoke Control]] · [[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]

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Category:Smoke Control

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'''Smoke control''' covers the movement of smoke and the systems used to manage its paths and accumulation within buildings. Topics include [[Smoke movement|smoke movement]], [[Smoke and heat exhaust ventilation|smoke and heat exhaust ventilation]], [[Stair pressurisation|stair pressurisation]], smoke barriers and smoke reservoirs.

Articles examine airflow, pressure differences, replacement air, stratification and the behaviour of smoke in larger spaces. The category also includes [[Atrium smoke control|atrium smoke control]] and plume behaviour at balconies. It connects the physical processes that transport smoke with the arrangements used to protect particular spaces and routes during a fire.

'''Related categories:''' [[:Category:Enclosure Fires|Enclosure Fires]] · [[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]] · [[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]

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Category:Physics & Heat Transfer

2026-11-02T15:14:06Z

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'''Physics and heat transfer''' brings together the physical principles and material properties used throughout fire safety engineering. It includes [[Conduction|conduction]], [[Convection|convection]] and [[Thermal radiation|thermal radiation]], along with heat flux, emissivity and the relationships used to describe energy transfer.

Articles also cover [[Buoyancy|buoyancy]], gas behaviour, thermal conductivity, heat capacity and [[Thermal inertia|thermal inertia]]. The category connects the movement of energy and gases with the heating of fuels, building elements and surrounding spaces. These principles form a basis for analysing ignition, fire growth, smoke movement and the response of materials to fire exposure.

'''Related categories:''' [[:Category:Ignition & Flame Spread|Ignition & Flame Spread]] · [[:Category:Fire Dynamics|Fire Dynamics]] · [[:Category:Structural Fire Engineering|Structural Fire Engineering]]

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Category:Passive Fire Protection

2026-11-02T15:14:00Z

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'''Passive fire protection''' covers construction features and protective materials used to limit fire spread and protect building elements. It includes [[Fire compartmentation|fire compartmentation]], [[Fire door|fire doors]], fire walls, [[Firestopping|firestopping]], cavity barriers and fire-resistant glazing.

Articles examine the components that form fire separations, including openings, joints and service penetrations, as well as protective products such as [[Intumescent material|intumescent materials]]. The category connects individual components with their role in the wider building arrangement. It also provides links to the fire resistance, testing and structural topics used to describe and assess their performance.

'''Related categories:''' [[:Category:Materials & Fire Testing|Materials & Fire Testing]] · [[:Category:Structural Fire Engineering|Structural Fire Engineering]] · [[:Category:Enclosure Fires|Enclosure Fires]]

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Category:Materials & Fire Testing

2026-11-02T15:13:54Z

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'''Materials and fire testing''' covers the behaviour of materials and products under fire exposure, and the methods used to measure that behaviour. Topics include [[Combustibility|combustibility]], [[Reaction to fire|reaction to fire]], flame retardants, plastics and sandwich panels.

Articles introduce [[Fire testing|fire testing]], the [[Euroclass system|Euroclass system]], cone calorimetry, room corner tests and [[Fire resistance test|fire resistance testing]]. The category explains what different tests measure, how results are expressed and how test conditions affect their interpretation. It connects the contribution of materials to fire development with the assessment of construction elements under specified exposure conditions.

'''Related categories:''' [[:Category:Ignition & Flame Spread|Ignition & Flame Spread]] · [[:Category:Structural Fire Engineering|Structural Fire Engineering]] · [[:Category:Passive Fire Protection|Passive Fire Protection]]

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Category:Ignition & Flame Spread

2026-11-02T15:13:48Z

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'''Ignition and flame spread''' covers the onset of burning and the processes by which fire extends to additional fuel or surfaces. Articles address [[Ignition|ignition]], [[Ignition source|ignition sources]], autoignition, [[Self-heating|self-heating]] and the conditions associated with sustained combustion.

The category includes [[Flame spread|flame spread]] in different directions, fire spread between buildings and transitions from smouldering to flaming. It also covers quantities used in ignition assessment, such as [[Time to ignition|time to ignition]] and critical heat flux. Together, these topics link fuel properties and heat exposure with the early development and subsequent spread of fire.

'''Related categories:''' [[:Category:Combustion|Combustion]] · [[:Category:Physics & Heat Transfer|Physics & Heat Transfer]] · [[:Category:Materials & Fire Testing|Materials & Fire Testing]]

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Category:Human Behaviour & Evacuation

2026-11-02T15:13:42Z

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'''Human behaviour and evacuation''' covers how people recognise fire cues, interpret warnings, make decisions and move towards safety. Topics include [[Human behaviour in fire|human behaviour in fire]], [[Pre-movement time|pre-movement time]], social responses and [[Evacuation|evacuation]] strategies.

Articles examine escape routes, walking speed, exit capacity, signs, emergency lighting and the evacuation of people with disabilities. The category also includes [[Available safe egress time|available safe egress time]], [[Required safe egress time|required safe egress time]] and evacuation modelling. These topics connect the actions and needs of occupants with building layout, warning systems and the changing fire environment.

'''Related categories:''' [[:Category:Detection & Alarm|Detection & Alarm]] · [[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]] · [[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Firefighting & Fire Service

2026-11-02T15:13:36Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Firefighting and the fire service''' covers manual fire suppression, supporting equipment and the building provisions used during fire service operations. Topics include [[Firefighting|firefighting]], [[Fire extinguisher|portable extinguishers]], hose reels, [[Fire hydrant|hydrants]] and dry and wet risers.

Articles also examine [[Fire service access|fire service access]], firefighting lifts, fire classes and [[Fire investigation|fire investigation]]. The category connects fire behaviour with the equipment, access and information relevant to intervention. It considers both the means of delivering extinguishing agents and the features of buildings that affect the movement of personnel and equipment during an incident.

'''Related categories:''' [[:Category:Fire Suppression|Fire Suppression]] · [[:Category:Enclosure Fires|Enclosure Fires]] · [[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Fire Suppression

2026-11-02T15:13:30Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Fire suppression''' covers the systems, agents and mechanisms used to control or extinguish fires. It includes [[Sprinkler system|sprinkler systems]], [[Water mist system|water mist systems]], [[Gaseous extinguishing system|gaseous systems]] and firefighting foam, together with the [[Extinguishing mechanisms|physical and chemical mechanisms of extinguishment]].

Articles examine system arrangements, activation, agent delivery, water supplies and [[Hydraulic calculation|hydraulic calculations]]. The category also addresses sprinkler response, design density, hazard classification and interactions with ventilation. These topics connect the intended suppression function with the characteristics of the protected fuel, the space and the equipment used to deliver the extinguishing agent.

'''Related categories:''' [[:Category:Combustion|Combustion]] · [[:Category:Detection & Alarm|Detection & Alarm]] · [[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Fire Safety Design & Regulation

2026-11-02T15:13:24Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Fire safety design and regulation''' covers the objectives, approaches and frameworks used to develop and assess a fire safety strategy. It includes [[Fire safety engineering|fire safety engineering]], [[Prescriptive design|prescriptive design]], [[Performance-based design|performance-based design]] and the relationship between engineering analysis and [[Building regulations|building regulations]].

Articles address fire scenarios, acceptance criteria, equivalency, professional ethics and [[Fire safety management|fire safety management]]. The category also introduces standards and professional organisations relevant to the field. Its focus is the connection between design objectives, regulatory requirements and supporting evidence; the application of particular rules depends on their jurisdiction and the documents concerned.

'''Related categories:''' [[:Category:Fire Risk Analysis|Fire Risk Analysis]] · [[:Category:Fire Modelling|Fire Modelling]] · [[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Fire Risk Analysis

2026-11-02T15:13:18Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Fire risk analysis''' covers methods for identifying fire hazards, examining possible outcomes and considering their likelihood and consequences. It includes [[Fire risk assessment|fire risk assessment]], [[Quantitative risk assessment|quantitative risk assessment]], fire statistics and the distinction between individual and societal risk.

Articles examine structured approaches such as [[Event tree analysis|event tree analysis]] and fault tree analysis, together with [[Reliability of fire protection systems|system reliability]] and common cause failure. The category also addresses [[Uncertainty analysis|uncertainty analysis]], probability models and Monte Carlo simulation. These topics support the comparison of scenarios, protective measures and design assumptions within a fire safety assessment.

'''Related categories:''' [[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]] · [[:Category:Fire Modelling|Fire Modelling]] · [[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Fire Modelling

2026-11-02T15:13:12Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Fire modelling''' covers methods used to represent fires, smoke movement and their effects through calculations and simulations. It includes [[Hand calculations|hand calculations]], [[Zone model|zone models]], [[Computational fluid dynamics|computational fluid dynamics]] and software such as [[Fire Dynamics Simulator|Fire Dynamics Simulator]] and CFAST.

Articles examine model assumptions, input data, numerical resolution and scaling, as well as the interpretation of results. [[Verification and validation]] and sensitivity analysis address how models are checked and how their outputs depend on modelling choices. The category also includes network models and finite element analysis, connecting different approaches to the questions they are intended to investigate.

'''Related categories:''' [[:Category:Fire Dynamics|Fire Dynamics]] · [[:Category:Fire Risk Analysis|Fire Risk Analysis]] · [[:Category:Structural Fire Engineering|Structural Fire Engineering]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Fire Dynamics

2026-11-02T15:13:06Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Fire dynamics''' covers the physical processes that govern how fires grow, release heat and interact with their surroundings. Central topics include [[Heat release rate|heat release rate]], [[Fire plume|fire plumes]], flame height, burning rate and the movement of hot gases beneath ceilings.

Articles connect fuel properties and [[Fire load|fire load]] with the development of a [[Design fire|design fire]]. The category also includes plume correlations, radiation models, entrainment and turbulence. These topics provide the physical relationships used to describe fire size, gas flow and thermal exposure in analyses of smoke movement, building protection and fire effects.

'''Related categories:''' [[:Category:Combustion|Combustion]] · [[:Category:Physics & Heat Transfer|Physics & Heat Transfer]] · [[:Category:Enclosure Fires|Enclosure Fires]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Explosions & Industrial Fires

2026-11-02T15:13:00Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Explosions and industrial fires''' brings together articles on rapid energy release and fires involving industrial fuels and processes. Topics include [[Explosion|explosions]], [[Dust explosion|dust explosions]], vapour cloud explosions, [[Pool fire|pool fires]], jet fires and fireballs.

The category examines different combustion and pressure-development mechanisms, including [[Deflagration|deflagration]] and detonation. It also covers ignition characteristics, hydrogen hazards, [[Inerting|inerting]] and explosion venting, alongside methods used to describe explosion severity and consequences. The articles distinguish between different fuels, release conditions and forms of confinement rather than treating industrial fire and explosion events as a single type of hazard.

'''Related categories:''' [[:Category:Combustion|Combustion]] · [[:Category:Fire Risk Analysis|Fire Risk Analysis]] · [[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Enclosure Fires

2026-11-02T15:08:43Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Enclosure fires''' covers fire behaviour within rooms and other enclosed spaces. Articles examine how fuel, ventilation, openings and heated boundaries interact during a [[Compartment fire|compartment fire]], including the formation of a [[Hot gas layer|hot gas layer]] and the transition to [[Flashover|flashover]].

The category includes fuel-controlled and [[Ventilation-controlled fire|ventilation-controlled fires]], post-flashover conditions, smoke filling and flows through openings. It also addresses phenomena such as [[Backdraft|backdraft]], rollover and external flaming. These topics provide a basis for understanding how enclosure conditions affect fire development, smoke accumulation and the exposure of neighbouring spaces and structural elements.

'''Related categories:''' [[:Category:Fire Dynamics|Fire Dynamics]] · [[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]] · [[:Category:Structural Fire Engineering|Structural Fire Engineering]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Detection & Alarm

2026-11-02T15:08:37Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Detection and alarm''' covers the systems and devices used to identify fires and communicate warnings. It includes [[Fire alarm system|fire alarm systems]], automatic [[Smoke detector|smoke detection]], heat and flame detection, manual call points and [[Voice alarm system|voice alarms]].

Articles examine detector types, [[Detector activation time|activation time]], notification methods and [[Unwanted fire alarms|unwanted fire alarms]]. They describe how detection and warning functions relate to building conditions, evacuation and other fire safety systems. The category distinguishes the recognition of fire conditions from the communication of information that enables people and systems to respond.

'''Related categories:''' [[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]] · [[:Category:Fire Dynamics|Fire Dynamics]] · [[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Category:Combustion

2026-11-02T15:08:31Z

Thomas: Add an English category introduction, topic links and related-category navigation.

'''Combustion''' brings together articles on the chemical reactions and fuel properties that underpin fire. Topics include [[Combustion|combustion]], [[Pyrolysis|pyrolysis]], flaming and [[Smouldering|smouldering]], together with flammability and flame extinction.

The category also covers the quantities used to describe fuel–air mixtures and energy release, including [[Heat of combustion|heat of combustion]], [[Stoichiometry|stoichiometry]], equivalence ratio and oxygen consumption. These articles connect chemical processes with the measurements and calculations used in fire analysis, from the behaviour of individual fuels to the production of heat and combustion products.

'''Related categories:''' [[:Category:Physics & Heat Transfer|Physics & Heat Transfer]] · [[:Category:Ignition & Flame Spread|Ignition & Flame Spread]] · [[:Category:Fire Dynamics|Fire Dynamics]]

[[Main Page|Wiki home]] · [[Special:Categories|All categories]] · [[Special:AllPages|All articles (A–Z)]]

Main Page

2026-11-01T22:08:24Z

Thomas: Balance homepage styling: compact welcome panel and lightly tinted subject groups, retaining prominent AllPages and no learning levels.

__NOTOC__
__NOEDITSECTION__

<div id="fsa-home">

<div id="fsa-welcome" style="background:#F5F7FA; color:#243649; border:1px solid #D9E1E8; border-top:3px solid #55758F; border-radius:4px; padding:1.2em 1.4em; margin:0 0 1.7em;">
<div style="display:flex; flex-wrap:wrap; align-items:center; justify-content:space-between; gap:0.7em 1.5em;">
<h2 style="font-family:inherit; font-size:1.6em; font-weight:600; line-height:1.25; border:0; margin:0; padding:0; color:#253F56;">Fire Safety Academy Wiki</h2>
<div id="fsa-allpages-link">[[Special:AllPages|<span style="display:inline-flex; align-items:center; box-sizing:border-box; min-height:44px; padding:0.55em 1em; border:1px solid #B1C4D4; border-radius:3px; background:#E9F0F6; color:#254E71; font-weight:bold;">All articles (A–Z)</span>]]</div>
</div>
<div id="fsa-home-index" style="display:flex; flex-wrap:wrap; align-items:center; justify-content:space-between; gap:0.75em 1.5em; margin-top:0.75em;">
<p style="flex:1 1 450px; min-width:0; margin:0; line-height:1.6;">A growing reference on fire science, building protection and fire safety engineering. Browse all articles or explore a subject below.</p>
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== Browse by subject ==
Select a category or go straight to one of its articles.

<div id="fsa-subject-index" style="display:flex; flex-wrap:wrap; align-items:stretch; gap:1.2em; margin:1.1em 0 1.5em;">
<div class="fsa-subject-group" style="flex:1 1 285px; min-width:0; border:1px solid #DCE3E9; border-radius:4px; overflow:hidden; background:#FFFFFF; color:#202122;">
<div style="background:#FAF5EF; color:#202122; padding:1em 1.1em; border-bottom:1px solid #DCE3E9;">
<h3 style="font-family:inherit; font-size:1.16em; font-weight:600; color:#95512D; margin:0 0 0.3em; padding:0;">Fire science</h3>
<p style="font-size:0.94em; line-height:1.5; margin:0; color:#52606D;">Combustion, heat transfer, fire growth and smoke.</p>
</div>
<div style="padding:0.1em 1.1em 0.2em;">
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Combustion|Combustion]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Combustion]] · [[Fire triangle]] · [[Stoichiometry]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Physics & Heat Transfer|Physics & Heat Transfer]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Heat transfer]] · [[Thermal diffusivity]] · [[Thermal inertia]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Ignition & Flame Spread|Ignition & Flame Spread]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Flame spread]] · [[Ignition]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Fire Dynamics|Fire Dynamics]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Design fire]] · [[Fire plume]] · [[Heat release rate]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Enclosure Fires|Enclosure Fires]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Compartment fire]] · [[Flashover]] · [[MQH correlation]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; ">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Smoke]] · [[Tenability criteria]]</div>
</div>
</div>
</div>
<div class="fsa-subject-group" style="flex:1 1 285px; min-width:0; border:1px solid #DCE3E9; border-radius:4px; overflow:hidden; background:#FFFFFF; color:#202122;">
<div style="background:#F0F5F9; color:#202122; padding:1em 1.1em; border-bottom:1px solid #DCE3E9;">
<h3 style="font-family:inherit; font-size:1.16em; font-weight:600; color:#355E7A; margin:0 0 0.3em; padding:0;">Buildings & protection</h3>
<p style="font-size:0.94em; line-height:1.5; margin:0; color:#52606D;">Materials, structures and fire protection systems.</p>
</div>
<div style="padding:0.1em 1.1em 0.2em;">
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Materials & Fire Testing|Materials & Fire Testing]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Fire testing]] · [[Reaction to fire]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Structural Fire Engineering|Structural Fire Engineering]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Fire resistance]] · [[Steel in fire]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Passive Fire Protection|Passive Fire Protection]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Fire compartmentation]] · [[Firestopping]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Detection & Alarm|Detection & Alarm]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Fire alarm system]] · [[Smoke detector]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Fire Suppression|Fire Suppression]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Sprinkler system]] · [[Water mist system]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; ">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Smoke Control|Smoke Control]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Smoke control]] · [[Stair pressurisation]]</div>
</div>
</div>
</div>
<div class="fsa-subject-group" style="flex:1 1 285px; min-width:0; border:1px solid #DCE3E9; border-radius:4px; overflow:hidden; background:#FFFFFF; color:#202122;">
<div style="background:#F0F6F4; color:#202122; padding:1em 1.1em; border-bottom:1px solid #DCE3E9;">
<h3 style="font-family:inherit; font-size:1.16em; font-weight:600; color:#356B65; margin:0 0 0.3em; padding:0;">People & practice</h3>
<p style="font-size:0.94em; line-height:1.5; margin:0; color:#52606D;">Evacuation, engineering methods and specialist risks.</p>
</div>
<div style="padding:0.1em 1.1em 0.2em;">
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Available safe egress time|Available safe egress time (ASET)]] · [[Evacuation]] · [[Human behaviour in fire]] · [[Required safe egress time|Required safe egress time (RSET)]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Fire Modelling|Fire Modelling]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Computational fluid dynamics|Computational fluid dynamics (CFD)]] · [[Fire Dynamics Simulator|Fire Dynamics Simulator (FDS)]] · [[Fire modelling]] · [[Mesh resolution]] · [[Sensitivity analysis]] · [[Verification and validation]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Building regulations]] · [[Fire safety engineering]] · [[Fire safety strategy]] · [[Performance-based design]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Fire Risk Analysis|Fire Risk Analysis]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Fire risk assessment]] · [[Quantitative risk assessment|Quantitative risk assessment (QRA)]] · [[Uncertainty analysis]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Explosions & Industrial Fires|Explosions & Industrial Fires]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Explosion]] · [[Hydrogen safety]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; border-bottom:1px solid #EBEEF1;">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[Fire service access]] · [[Firefighting]]</div>
</div>
<div class="fsa-category-block" style="padding:0.7em 0; ">
<div style="font-weight:bold; line-height:1.45;">[[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]</div>
<div style="font-size:0.94em; line-height:1.7; margin-top:0.25em;">[[High-rise building]] · [[Lithium-ion battery fire]]</div>
</div>
</div>
</div>
</div>

<div style="border-top:1px solid #DCE3E9; padding-top:0.8em; font-size:0.94em;">
<p style="margin:0 0 0.4em;">The wiki is being expanded. Red links lead to pages that have not yet been created.</p>
<p style="margin:0;">[[Special:Categories|Category index]] · [[Special:RecentChanges|Recent changes]] · [[Talk:Main Page|Discuss this page]]</p>
</div>

</div>

Main Page

2026-11-01T22:03:45Z

Thomas: Place a prominent All articles (A–Z) link to Special:AllPages at the very top, before the introduction.

__NOTOC__
__NOEDITSECTION__

<div id="fsa-home">

<div id="fsa-home-index" style="display:flex; flex-wrap:wrap; align-items:center; justify-content:space-between; gap:0.6em 1.5em; margin:0 0 1em; padding:0.65em 0; border-top:1px solid #c8ccd1; border-bottom:1px solid #c8ccd1;">
<div id="fsa-allpages-link" style="font-size:1.25em;">'''[[Special:AllPages|All articles (A–Z)]]'''</div>
<div style="max-width:100%;">
<inputbox>
type=fulltext
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arialabel=Search the Fire Safety Academy Wiki
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'''Fire Safety Academy Wiki''' is a growing reference on fire science, building protection and fire safety engineering. Browse the subjects below or use the alphabetical article index.

== Browse by subject ==
Select a category to browse its articles, or follow one of the links listed beneath it.

<div id="fsa-subject-index" style="column-width:21em; column-gap:2em; margin-top:1em;">
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Combustion|Combustion]]
: [[Combustion]] · [[Fire triangle]] · [[Stoichiometry]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Detection & Alarm|Detection & Alarm]]
: [[Fire alarm system]] · [[Smoke detector]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Enclosure Fires|Enclosure Fires]]
: [[Compartment fire]] · [[Flashover]] · [[MQH correlation]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Explosions & Industrial Fires|Explosions & Industrial Fires]]
: [[Explosion]] · [[Hydrogen safety]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Dynamics|Fire Dynamics]]
: [[Design fire]] · [[Fire plume]] · [[Heat release rate]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Modelling|Fire Modelling]]
: [[Computational fluid dynamics|Computational fluid dynamics (CFD)]] · [[Fire Dynamics Simulator|Fire Dynamics Simulator (FDS)]] · [[Fire modelling]] · [[Mesh resolution]] · [[Sensitivity analysis]] · [[Verification and validation]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Risk Analysis|Fire Risk Analysis]]
: [[Fire risk assessment]] · [[Quantitative risk assessment|Quantitative risk assessment (QRA)]] · [[Uncertainty analysis]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]
: [[Building regulations]] · [[Fire safety engineering]] · [[Fire safety strategy]] · [[Performance-based design]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Suppression|Fire Suppression]]
: [[Sprinkler system]] · [[Water mist system]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]
: [[Fire service access]] · [[Firefighting]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]
: [[Available safe egress time|Available safe egress time (ASET)]] · [[Evacuation]] · [[Human behaviour in fire]] · [[Required safe egress time|Required safe egress time (RSET)]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Ignition & Flame Spread|Ignition & Flame Spread]]
: [[Flame spread]] · [[Ignition]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Materials & Fire Testing|Materials & Fire Testing]]
: [[Fire testing]] · [[Reaction to fire]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Passive Fire Protection|Passive Fire Protection]]
: [[Fire compartmentation]] · [[Firestopping]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Physics & Heat Transfer|Physics & Heat Transfer]]
: [[Heat transfer]] · [[Thermal diffusivity]] · [[Thermal inertia]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Smoke Control|Smoke Control]]
: [[Smoke control]] · [[Stair pressurisation]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]]
: [[Smoke]] · [[Tenability criteria]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]
: [[High-rise building]] · [[Lithium-ion battery fire]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Structural Fire Engineering|Structural Fire Engineering]]
: [[Fire resistance]] · [[Steel in fire]]
</div>
</div>

== About this wiki ==
The wiki connects related concepts through internal links and references. It is being expanded: red links lead to pages that have not yet been created.

[[Special:Categories|Category index]] · [[Special:RecentChanges|Recent changes]] · [[Talk:Main Page|Discuss this page]]

</div>

Main Page

2026-11-01T22:02:24Z

Thomas: Simplify homepage to a conventional wiki subject index; remove learning levels and decorative cards; keep AllPages prominent.

__NOTOC__
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<div id="fsa-home">

'''Fire Safety Academy Wiki''' is a growing reference on fire science, building protection and fire safety engineering. Browse the subjects below or use the alphabetical article index.

<div id="fsa-home-index" style="display:flex; flex-wrap:wrap; align-items:center; justify-content:space-between; gap:0.6em 1.5em; margin:1em 0 1.4em; padding:0.65em 0; border-top:1px solid #c8ccd1; border-bottom:1px solid #c8ccd1;">
<div id="fsa-allpages-link" style="font-size:1.12em;">'''[[Special:AllPages|Browse all articles (A–Z)]]'''</div>
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== Browse by subject ==
Select a category to browse its articles, or follow one of the links listed beneath it.

<div id="fsa-subject-index" style="column-width:21em; column-gap:2em; margin-top:1em;">
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Combustion|Combustion]]
: [[Combustion]] · [[Fire triangle]] · [[Stoichiometry]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Detection & Alarm|Detection & Alarm]]
: [[Fire alarm system]] · [[Smoke detector]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Enclosure Fires|Enclosure Fires]]
: [[Compartment fire]] · [[Flashover]] · [[MQH correlation]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Explosions & Industrial Fires|Explosions & Industrial Fires]]
: [[Explosion]] · [[Hydrogen safety]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Dynamics|Fire Dynamics]]
: [[Design fire]] · [[Fire plume]] · [[Heat release rate]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Modelling|Fire Modelling]]
: [[Computational fluid dynamics|Computational fluid dynamics (CFD)]] · [[Fire Dynamics Simulator|Fire Dynamics Simulator (FDS)]] · [[Fire modelling]] · [[Mesh resolution]] · [[Sensitivity analysis]] · [[Verification and validation]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Risk Analysis|Fire Risk Analysis]]
: [[Fire risk assessment]] · [[Quantitative risk assessment|Quantitative risk assessment (QRA)]] · [[Uncertainty analysis]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]
: [[Building regulations]] · [[Fire safety engineering]] · [[Fire safety strategy]] · [[Performance-based design]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Fire Suppression|Fire Suppression]]
: [[Sprinkler system]] · [[Water mist system]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]
: [[Fire service access]] · [[Firefighting]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]
: [[Available safe egress time|Available safe egress time (ASET)]] · [[Evacuation]] · [[Human behaviour in fire]] · [[Required safe egress time|Required safe egress time (RSET)]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Ignition & Flame Spread|Ignition & Flame Spread]]
: [[Flame spread]] · [[Ignition]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Materials & Fire Testing|Materials & Fire Testing]]
: [[Fire testing]] · [[Reaction to fire]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Passive Fire Protection|Passive Fire Protection]]
: [[Fire compartmentation]] · [[Firestopping]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Physics & Heat Transfer|Physics & Heat Transfer]]
: [[Heat transfer]] · [[Thermal diffusivity]] · [[Thermal inertia]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Smoke Control|Smoke Control]]
: [[Smoke control]] · [[Stair pressurisation]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]]
: [[Smoke]] · [[Tenability criteria]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]
: [[High-rise building]] · [[Lithium-ion battery fire]]
</div>
<div class="fsa-category-block" style="break-inside:avoid; margin:0 0 1.1em;">
; [[:Category:Structural Fire Engineering|Structural Fire Engineering]]
: [[Fire resistance]] · [[Steel in fire]]
</div>
</div>

== About this wiki ==
The wiki connects related concepts through internal links and references. It is being expanded: red links lead to pages that have not yet been created.

[[Special:Categories|Category index]] · [[Special:RecentChanges|Recent changes]] · [[Talk:Main Page|Discuss this page]]

</div>

Main Page

2026-11-01T21:57:58Z

Thomas: Ensure the prominent article-index button has a comfortable touch target on mobile.

__NOTOC__
__NOEDITSECTION__

<div id="fsa-home" style="font-family:Arial,Helvetica,sans-serif; line-height:1.6; color:#243649; background:#FFFFFF;">

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<div style="font-size:0.76em; font-weight:bold; letter-spacing:0.16em; color:#C0D4E7;">FIRE SAFETY ACADEMY · WIKI</div>
<div role="heading" aria-level="2" style="font-size:clamp(29px,3.5vw,45px); font-weight:700; letter-spacing:-0.035em; line-height:1.16; margin:0.38em 0 0.5em; color:#FFFFFF;">Fire safety engineering.<br /><span style="color:#F5B17B;">From fundamentals<br />to expert practice.</span></div>
<p style="font-size:1.03em; color:#DDE8F2; max-width:41em; margin:0;">A growing reference for students, engineers and fire safety professionals. Explore the science of fire, building protection and the methods used to assess safety.</p>
<div style="margin-top:1.35em;">[[Special:AllPages|<span id="fsa-allpages-button" style="display:inline-block; box-sizing:border-box; max-width:100%; min-height:44px; padding:0.9em 1.15em; border-radius:6px; background:#F5B17B; color:#142B42; font-size:1em; font-weight:bold; line-height:1.4;">Browse all articles (A–Z)</span>]]</div>
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<div style="font-size:0.75em; color:#C0D4E7; font-weight:bold; letter-spacing:0.12em; margin-bottom:1.25em;">A CONNECTED FIELD OF KNOWLEDGE</div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#F5B17B; font-size:1.3em; font-weight:bold;">01</span><span>Understand fire</span></div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#A8D4F4; font-size:1.3em; font-weight:bold;">02</span><span>Protect buildings</span></div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#98DDD5; font-size:1.3em; font-weight:bold;">03</span><span>Assess safety</span></div>
<div style="border-top:1px solid #46617A; color:#C0D4E7; padding-top:1em; margin-top:1.2em; font-size:0.85em;">4 learning levels · 19 subject areas</div>
</div>
</div>
</div>

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<div style="display:flex; flex-wrap:wrap; gap:0.35em 1.35em; font-size:0.91em;"><strong>Explore:</strong> [[#Learning_levels|Learning levels]] [[#Subject_areas|Subject areas]] [[Special:AllPages|A–Z index]]</div>
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<h2 id="Learning_levels" style="font-family:Arial,Helvetica,sans-serif; font-size:1.55em; font-weight:700; color:#142B42; border:0; margin:0 0 0.2em; padding:0;">Choose a starting point</h2>
<p style="color:#526475; margin:0 0 1.2em;">Four levels of depth, from first principles to specialist analysis. Start with one of these topics.</p>
<div style="display:flex; flex-wrap:wrap; gap:1em; align-items:stretch; margin-bottom:2.4em;">
<div style="display:flex; flex-wrap:wrap; flex:1 1 420px; min-width:0; gap:1em; align-items:stretch;">
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<div style="padding:1.2em 1.2em 0.8em;">
<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#1971C2;">LEVEL 01</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Basic</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Start with the essentials</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Clear explanations of what fire safety concepts mean and why they matter.</p>
</div>
<div style="padding:0.75em 1.2em 1.2em; font-size:0.89em;">
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Fire safety engineering]]</li>
<li style="margin:0.3em 0;">[[Fire triangle]]</li>
<li style="margin:0.3em 0;">[[Heat transfer]]</li>
<li style="margin:0.3em 0;">[[Compartment fire]]</li>
</ul>
</div>
</div>
<div style="flex:1 1 200px; min-width:0; border:1px solid #DCE3EA; border-top:4px solid #0C7889; border-radius:8px; overflow:hidden; background:#FFFFFF; color:#243649;">
<div style="padding:1.2em 1.2em 0.8em;">
<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#0C7889;">LEVEL 02</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Intermediate</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Understand how it works</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Explore physical principles, protection systems and the steps in fire safety design.</p>
</div>
<div style="padding:0.75em 1.2em 1.2em; font-size:0.89em;">
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Design fire]]</li>
<li style="margin:0.3em 0;">[[Fire safety strategy]]</li>
<li style="margin:0.3em 0;">[[Available safe egress time|Available safe egress time (ASET)]]</li>
<li style="margin:0.3em 0;">[[Required safe egress time|Required safe egress time (RSET)]]</li>
</ul>
</div>
</div>
</div>
<div style="display:flex; flex-wrap:wrap; flex:1 1 420px; min-width:0; gap:1em; align-items:stretch;">
<div style="flex:1 1 200px; min-width:0; border:1px solid #DCE3EA; border-top:4px solid #B84B15; border-radius:8px; overflow:hidden; background:#FFFFFF; color:#243649;">
<div style="padding:1.2em 1.2em 0.8em;">
<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#B84B15;">LEVEL 03</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Advanced</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Connect theory and calculation</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Study calculation methods, test methods and worked engineering examples.</p>
</div>
<div style="padding:0.75em 1.2em 1.2em; font-size:0.89em;">
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Thermal inertia]]</li>
<li style="margin:0.3em 0;">[[Tenability criteria]]</li>
<li style="margin:0.3em 0;">[[Fire Dynamics Simulator|Fire Dynamics Simulator (FDS)]]</li>
<li style="margin:0.3em 0;">[[Sensitivity analysis]]</li>
</ul>
</div>
</div>
<div style="flex:1 1 200px; min-width:0; border:1px solid #DCE3EA; border-top:4px solid #70489A; border-radius:8px; overflow:hidden; background:#FFFFFF; color:#243649;">
<div style="padding:1.2em 1.2em 0.8em;">
<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#70489A;">LEVEL 04</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Expert</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Examine models and uncertainty</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Investigate specialist models, detailed analyses and the limits of their application.</p>
</div>
<div style="padding:0.75em 1.2em 1.2em; font-size:0.89em;">
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[MQH correlation]]</li>
<li style="margin:0.3em 0;">[[Mesh resolution]]</li>
<li style="margin:0.3em 0;">[[Verification and validation]]</li>
<li style="margin:0.3em 0;">[[Uncertainty analysis]]</li>
</ul>
</div>
</div>
</div>
</div>

<h2 id="Subject_areas" style="font-family:Arial,Helvetica,sans-serif; font-size:1.55em; font-weight:700; color:#142B42; border:0; margin:0 0 0.2em; padding:0;">Explore by subject</h2>
<p style="color:#526475; margin:0 0 1.2em;">Browse all 19 categories, or go straight to an article below each category.</p>
<div style="display:flex; flex-wrap:wrap; gap:1.1em; align-items:stretch; margin-bottom:2em;">
<div style="flex:1 1 280px; min-width:0; border:1px solid #DCE3EA; border-radius:10px; overflow:hidden; background:#FFFFFF; color:#243649;">

<div style="background:#FFF4EC; color:#243649; padding:1.4em 1.3em 1.2em; border-top:4px solid #B84B15;">
<div style="font-size:0.75em; font-weight:bold; color:#B84B15; letter-spacing:0.1em;">SUBJECT COLLECTION 01</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Understand fire</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">From combustion and heat transfer to fire growth, smoke and its effects.</p>
</div>
<div style="padding:0.3em 1.3em 0.6em;">
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Combustion|Combustion]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Combustion]] · [[Stoichiometry]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Physics & Heat Transfer|Physics & Heat Transfer]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Heat transfer]] · [[Thermal diffusivity]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Ignition & Flame Spread|Ignition & Flame Spread]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Ignition]] · [[Flame spread]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Dynamics|Fire Dynamics]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Heat release rate]] · [[Fire plume]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Enclosure Fires|Enclosure Fires]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Compartment fire]] · [[Flashover]]</div>
</div>
<div style="padding:0.85em 0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Smoke]] · [[Tenability criteria]]</div>
</div>
</div>
</div>
<div style="flex:1 1 280px; min-width:0; border:1px solid #DCE3EA; border-radius:10px; overflow:hidden; background:#FFFFFF; color:#243649;">

<div style="background:#EDF5FC; color:#243649; padding:1.4em 1.3em 1.2em; border-top:4px solid #1971C2;">
<div style="font-size:0.75em; font-weight:bold; color:#1971C2; letter-spacing:0.1em;">SUBJECT COLLECTION 02</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Protect buildings</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">Materials, structures and the systems used to detect, contain and control fire.</p>
</div>
<div style="padding:0.3em 1.3em 0.6em;">
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Materials & Fire Testing|Materials & Fire Testing]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Reaction to fire]] · [[Fire testing]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Structural Fire Engineering|Structural Fire Engineering]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire resistance]] · [[Steel in fire]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Passive Fire Protection|Passive Fire Protection]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire compartmentation]] · [[Firestopping]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Detection & Alarm|Detection & Alarm]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire alarm system]] · [[Smoke detector]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Suppression|Fire Suppression]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Sprinkler system]] · [[Water mist system]]</div>
</div>
<div style="padding:0.85em 0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Smoke Control|Smoke Control]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Smoke control]] · [[Stair pressurisation]]</div>
</div>
</div>
</div>
<div style="flex:1 1 280px; min-width:0; border:1px solid #DCE3EA; border-radius:10px; overflow:hidden; background:#FFFFFF; color:#243649;">

<div style="background:#EDF8F8; color:#243649; padding:1.4em 1.3em 1.2em; border-top:4px solid #0C7889;">
<div style="font-size:0.75em; font-weight:bold; color:#0C7889; letter-spacing:0.1em;">SUBJECT COLLECTION 03</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Assess safety</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">People, modelling and risk, from design decisions to complex hazards and fire service operations.</p>
</div>
<div style="padding:0.3em 1.3em 0.6em;">
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Evacuation]] · [[Human behaviour in fire]]</div>
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<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Modelling|Fire Modelling]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire modelling]] · [[Computational fluid dynamics|Computational fluid dynamics (CFD)]]</div>
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<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Performance-based design]] · [[Building regulations]]</div>
</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Risk Analysis|Fire Risk Analysis]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire risk assessment]] · [[Quantitative risk assessment|Quantitative risk assessment (QRA)]]</div>
</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Explosions & Industrial Fires|Explosions & Industrial Fires]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Explosion]] · [[Hydrogen safety]]</div>
</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Firefighting]] · [[Fire service access]]</div>
</div>
<div style="padding:0.85em 0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Lithium-ion battery fire]] · [[High-rise building]]</div>
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<h2 style="font-family:Arial,Helvetica,sans-serif; font-size:1.12em; font-weight:bold; color:#142B42; margin:0 0 0.4em; padding:0; border:0;">About this knowledge base</h2>
<p style="font-size:0.88em; margin:0;">The Fire Safety Academy Wiki connects fire science with engineering practice. Articles are organised by subject and written at four levels of depth, with references and links to related concepts.</p>
<p style="font-size:0.84em; color:#526475; margin:0.6em 0 0;">The wiki is growing. Red links mark pages that have not yet been created.</p>
</div>
<div style="flex:1 1 200px; min-width:0; font-size:0.88em;">
<div style="font-weight:bold; margin-bottom:0.4em;">Keep exploring</div>
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Special:AllPages|All articles, A–Z]]</li>
<li style="margin:0.3em 0;">[[Special:Categories|Categories with articles]]</li>
<li style="margin:0.3em 0;">[[Special:RecentChanges|Recent changes]]</li>
<li style="margin:0.3em 0;">[[Talk:Main Page|Discuss this page]]</li>
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Main Page

2026-11-01T21:57:14Z

Thomas: Add prominent Browse all articles (A–Z) button linking to Special:AllPages in the homepage introduction.

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<div style="font-size:0.76em; font-weight:bold; letter-spacing:0.16em; color:#C0D4E7;">FIRE SAFETY ACADEMY · WIKI</div>
<div role="heading" aria-level="2" style="font-size:clamp(29px,3.5vw,45px); font-weight:700; letter-spacing:-0.035em; line-height:1.16; margin:0.38em 0 0.5em; color:#FFFFFF;">Fire safety engineering.<br /><span style="color:#F5B17B;">From fundamentals<br />to expert practice.</span></div>
<p style="font-size:1.03em; color:#DDE8F2; max-width:41em; margin:0;">A growing reference for students, engineers and fire safety professionals. Explore the science of fire, building protection and the methods used to assess safety.</p>
<div style="margin-top:1.35em;">[[Special:AllPages|<span id="fsa-allpages-button" style="display:inline-block; box-sizing:border-box; max-width:100%; padding:0.75em 1.15em; border-radius:6px; background:#F5B17B; color:#142B42; font-size:0.96em; font-weight:bold; line-height:1.4;">Browse all articles (A–Z)</span>]]</div>
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<div style="font-size:0.75em; color:#C0D4E7; font-weight:bold; letter-spacing:0.12em; margin-bottom:1.25em;">A CONNECTED FIELD OF KNOWLEDGE</div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#F5B17B; font-size:1.3em; font-weight:bold;">01</span><span>Understand fire</span></div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#A8D4F4; font-size:1.3em; font-weight:bold;">02</span><span>Protect buildings</span></div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#98DDD5; font-size:1.3em; font-weight:bold;">03</span><span>Assess safety</span></div>
<div style="border-top:1px solid #46617A; color:#C0D4E7; padding-top:1em; margin-top:1.2em; font-size:0.85em;">4 learning levels · 19 subject areas</div>
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<div style="display:flex; flex-wrap:wrap; gap:0.35em 1.35em; font-size:0.91em;"><strong>Explore:</strong> [[#Learning_levels|Learning levels]] [[#Subject_areas|Subject areas]] [[Special:AllPages|A–Z index]]</div>
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<h2 id="Learning_levels" style="font-family:Arial,Helvetica,sans-serif; font-size:1.55em; font-weight:700; color:#142B42; border:0; margin:0 0 0.2em; padding:0;">Choose a starting point</h2>
<p style="color:#526475; margin:0 0 1.2em;">Four levels of depth, from first principles to specialist analysis. Start with one of these topics.</p>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#1971C2;">LEVEL 01</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Basic</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Start with the essentials</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Clear explanations of what fire safety concepts mean and why they matter.</p>
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<div style="padding:0.75em 1.2em 1.2em; font-size:0.89em;">
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Fire safety engineering]]</li>
<li style="margin:0.3em 0;">[[Fire triangle]]</li>
<li style="margin:0.3em 0;">[[Heat transfer]]</li>
<li style="margin:0.3em 0;">[[Compartment fire]]</li>
</ul>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#0C7889;">LEVEL 02</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Intermediate</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Understand how it works</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Explore physical principles, protection systems and the steps in fire safety design.</p>
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<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Design fire]]</li>
<li style="margin:0.3em 0;">[[Fire safety strategy]]</li>
<li style="margin:0.3em 0;">[[Available safe egress time|Available safe egress time (ASET)]]</li>
<li style="margin:0.3em 0;">[[Required safe egress time|Required safe egress time (RSET)]]</li>
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<div style="padding:1.2em 1.2em 0.8em;">
<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#B84B15;">LEVEL 03</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Advanced</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Connect theory and calculation</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Study calculation methods, test methods and worked engineering examples.</p>
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<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Thermal inertia]]</li>
<li style="margin:0.3em 0;">[[Tenability criteria]]</li>
<li style="margin:0.3em 0;">[[Fire Dynamics Simulator|Fire Dynamics Simulator (FDS)]]</li>
<li style="margin:0.3em 0;">[[Sensitivity analysis]]</li>
</ul>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#70489A;">LEVEL 04</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Expert</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Examine models and uncertainty</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Investigate specialist models, detailed analyses and the limits of their application.</p>
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<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[MQH correlation]]</li>
<li style="margin:0.3em 0;">[[Mesh resolution]]</li>
<li style="margin:0.3em 0;">[[Verification and validation]]</li>
<li style="margin:0.3em 0;">[[Uncertainty analysis]]</li>
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<h2 id="Subject_areas" style="font-family:Arial,Helvetica,sans-serif; font-size:1.55em; font-weight:700; color:#142B42; border:0; margin:0 0 0.2em; padding:0;">Explore by subject</h2>
<p style="color:#526475; margin:0 0 1.2em;">Browse all 19 categories, or go straight to an article below each category.</p>
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<div style="font-size:0.75em; font-weight:bold; color:#B84B15; letter-spacing:0.1em;">SUBJECT COLLECTION 01</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Understand fire</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">From combustion and heat transfer to fire growth, smoke and its effects.</p>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Combustion|Combustion]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Combustion]] · [[Stoichiometry]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Physics & Heat Transfer|Physics & Heat Transfer]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Heat transfer]] · [[Thermal diffusivity]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Ignition & Flame Spread|Ignition & Flame Spread]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Ignition]] · [[Flame spread]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Dynamics|Fire Dynamics]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Heat release rate]] · [[Fire plume]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Enclosure Fires|Enclosure Fires]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Compartment fire]] · [[Flashover]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Smoke]] · [[Tenability criteria]]</div>
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<div style="font-size:0.75em; font-weight:bold; color:#1971C2; letter-spacing:0.1em;">SUBJECT COLLECTION 02</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Protect buildings</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">Materials, structures and the systems used to detect, contain and control fire.</p>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Materials & Fire Testing|Materials & Fire Testing]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Reaction to fire]] · [[Fire testing]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Structural Fire Engineering|Structural Fire Engineering]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire resistance]] · [[Steel in fire]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Passive Fire Protection|Passive Fire Protection]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire compartmentation]] · [[Firestopping]]</div>
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<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Detection & Alarm|Detection & Alarm]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire alarm system]] · [[Smoke detector]]</div>
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<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Suppression|Fire Suppression]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Sprinkler system]] · [[Water mist system]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Smoke Control|Smoke Control]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Smoke control]] · [[Stair pressurisation]]</div>
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<div style="font-size:0.75em; font-weight:bold; color:#0C7889; letter-spacing:0.1em;">SUBJECT COLLECTION 03</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Assess safety</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">People, modelling and risk, from design decisions to complex hazards and fire service operations.</p>
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<div style="padding:0.3em 1.3em 0.6em;">
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Evacuation]] · [[Human behaviour in fire]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Modelling|Fire Modelling]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire modelling]] · [[Computational fluid dynamics|Computational fluid dynamics (CFD)]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Performance-based design]] · [[Building regulations]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Risk Analysis|Fire Risk Analysis]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire risk assessment]] · [[Quantitative risk assessment|Quantitative risk assessment (QRA)]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Explosions & Industrial Fires|Explosions & Industrial Fires]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Explosion]] · [[Hydrogen safety]]</div>
</div>
<div style="padding:0.85em 0; border-bottom:1px solid #E6EBF0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Firefighting]] · [[Fire service access]]</div>
</div>
<div style="padding:0.85em 0; ">
<div style="font-size:0.96em; font-weight:bold;">[[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Lithium-ion battery fire]] · [[High-rise building]]</div>
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<h2 style="font-family:Arial,Helvetica,sans-serif; font-size:1.12em; font-weight:bold; color:#142B42; margin:0 0 0.4em; padding:0; border:0;">About this knowledge base</h2>
<p style="font-size:0.88em; margin:0;">The Fire Safety Academy Wiki connects fire science with engineering practice. Articles are organised by subject and written at four levels of depth, with references and links to related concepts.</p>
<p style="font-size:0.84em; color:#526475; margin:0.6em 0 0;">The wiki is growing. Red links mark pages that have not yet been created.</p>
</div>
<div style="flex:1 1 200px; min-width:0; font-size:0.88em;">
<div style="font-weight:bold; margin-bottom:0.4em;">Keep exploring</div>
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Main Page

2026-11-01T21:54:26Z

Thomas: Create FSA knowledge homepage: four learning levels, 19 subject categories, topic links and search.

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<div style="font-size:0.76em; font-weight:bold; letter-spacing:0.16em; color:#C0D4E7;">FIRE SAFETY ACADEMY · WIKI</div>
<div role="heading" aria-level="2" style="font-size:clamp(29px,3.5vw,45px); font-weight:700; letter-spacing:-0.035em; line-height:1.16; margin:0.38em 0 0.5em; color:#FFFFFF;">Fire safety engineering.<br /><span style="color:#F5B17B;">From fundamentals<br />to expert practice.</span></div>
<p style="font-size:1.03em; color:#DDE8F2; max-width:41em; margin:0;">A growing reference for students, engineers and fire safety professionals. Explore the science of fire, building protection and the methods used to assess safety.</p>
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<div style="font-size:0.75em; color:#C0D4E7; font-weight:bold; letter-spacing:0.12em; margin-bottom:1.25em;">A CONNECTED FIELD OF KNOWLEDGE</div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#F5B17B; font-size:1.3em; font-weight:bold;">01</span><span>Understand fire</span></div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#A8D4F4; font-size:1.3em; font-weight:bold;">02</span><span>Protect buildings</span></div>
<div style="display:flex; align-items:center; gap:0.8em; margin:0.9em 0;"><span style="color:#98DDD5; font-size:1.3em; font-weight:bold;">03</span><span>Assess safety</span></div>
<div style="border-top:1px solid #46617A; color:#C0D4E7; padding-top:1em; margin-top:1.2em; font-size:0.85em;">4 learning levels · 19 subject areas</div>
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<div style="display:flex; flex-wrap:wrap; gap:0.35em 1.35em; font-size:0.91em;"><strong>Explore:</strong> [[#Learning_levels|Learning levels]] [[#Subject_areas|Subject areas]] [[Special:AllPages|A–Z index]]</div>
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<h2 id="Learning_levels" style="font-family:Arial,Helvetica,sans-serif; font-size:1.55em; font-weight:700; color:#142B42; border:0; margin:0 0 0.2em; padding:0;">Choose a starting point</h2>
<p style="color:#526475; margin:0 0 1.2em;">Four levels of depth, from first principles to specialist analysis. Start with one of these topics.</p>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#1971C2;">LEVEL 01</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Basic</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Start with the essentials</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Clear explanations of what fire safety concepts mean and why they matter.</p>
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<li style="margin:0.3em 0;">[[Fire safety engineering]]</li>
<li style="margin:0.3em 0;">[[Fire triangle]]</li>
<li style="margin:0.3em 0;">[[Heat transfer]]</li>
<li style="margin:0.3em 0;">[[Compartment fire]]</li>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#0C7889;">LEVEL 02</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Intermediate</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Understand how it works</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Explore physical principles, protection systems and the steps in fire safety design.</p>
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<li style="margin:0.3em 0;">[[Design fire]]</li>
<li style="margin:0.3em 0;">[[Fire safety strategy]]</li>
<li style="margin:0.3em 0;">[[Available safe egress time|Available safe egress time (ASET)]]</li>
<li style="margin:0.3em 0;">[[Required safe egress time|Required safe egress time (RSET)]]</li>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#B84B15;">LEVEL 03</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Advanced</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Connect theory and calculation</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Study calculation methods, test methods and worked engineering examples.</p>
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<li style="margin:0.3em 0;">[[Thermal inertia]]</li>
<li style="margin:0.3em 0;">[[Tenability criteria]]</li>
<li style="margin:0.3em 0;">[[Fire Dynamics Simulator|Fire Dynamics Simulator (FDS)]]</li>
<li style="margin:0.3em 0;">[[Sensitivity analysis]]</li>
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<div style="font-size:0.76em; letter-spacing:0.09em; font-weight:bold; color:#70489A;">LEVEL 04</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; font-size:1.25em; color:#142B42; padding:0; margin:0.2em 0 0.55em;">Expert</h3>
<div style="font-size:0.91em; font-weight:bold; margin-bottom:0.4em;">Examine models and uncertainty</div>
<p style="font-size:0.88em; color:#526475; margin:0;">Investigate specialist models, detailed analyses and the limits of their application.</p>
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<li style="margin:0.3em 0;">[[MQH correlation]]</li>
<li style="margin:0.3em 0;">[[Mesh resolution]]</li>
<li style="margin:0.3em 0;">[[Verification and validation]]</li>
<li style="margin:0.3em 0;">[[Uncertainty analysis]]</li>
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<h2 id="Subject_areas" style="font-family:Arial,Helvetica,sans-serif; font-size:1.55em; font-weight:700; color:#142B42; border:0; margin:0 0 0.2em; padding:0;">Explore by subject</h2>
<p style="color:#526475; margin:0 0 1.2em;">Browse all 19 categories, or go straight to an article below each category.</p>
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<div style="font-size:0.75em; font-weight:bold; color:#B84B15; letter-spacing:0.1em;">SUBJECT COLLECTION 01</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Understand fire</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">From combustion and heat transfer to fire growth, smoke and its effects.</p>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Combustion|Combustion]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Combustion]] · [[Stoichiometry]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Physics & Heat Transfer|Physics & Heat Transfer]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Heat transfer]] · [[Thermal diffusivity]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Ignition & Flame Spread|Ignition & Flame Spread]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Ignition]] · [[Flame spread]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Dynamics|Fire Dynamics]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Heat release rate]] · [[Fire plume]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Enclosure Fires|Enclosure Fires]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Compartment fire]] · [[Flashover]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Smoke, Toxicity & Tenability|Smoke, Toxicity & Tenability]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Smoke]] · [[Tenability criteria]]</div>
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<div style="font-size:0.75em; font-weight:bold; color:#1971C2; letter-spacing:0.1em;">SUBJECT COLLECTION 02</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Protect buildings</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">Materials, structures and the systems used to detect, contain and control fire.</p>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Materials & Fire Testing|Materials & Fire Testing]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Reaction to fire]] · [[Fire testing]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Structural Fire Engineering|Structural Fire Engineering]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire resistance]] · [[Steel in fire]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Passive Fire Protection|Passive Fire Protection]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire compartmentation]] · [[Firestopping]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Detection & Alarm|Detection & Alarm]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire alarm system]] · [[Smoke detector]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Suppression|Fire Suppression]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Sprinkler system]] · [[Water mist system]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Smoke Control|Smoke Control]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Smoke control]] · [[Stair pressurisation]]</div>
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<div style="font-size:0.75em; font-weight:bold; color:#0C7889; letter-spacing:0.1em;">SUBJECT COLLECTION 03</div>
<h3 style="font-family:Arial,Helvetica,sans-serif; color:#142B42; font-size:1.35em; margin:0.3em 0 0.45em; padding:0;">Assess safety</h3>
<p style="font-size:0.89em; color:#43576A; margin:0;">People, modelling and risk, from design decisions to complex hazards and fire service operations.</p>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Human Behaviour & Evacuation|Human Behaviour & Evacuation]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Evacuation]] · [[Human behaviour in fire]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Modelling|Fire Modelling]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire modelling]] · [[Computational fluid dynamics|Computational fluid dynamics (CFD)]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Safety Design & Regulation|Fire Safety Design & Regulation]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Performance-based design]] · [[Building regulations]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Fire Risk Analysis|Fire Risk Analysis]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Fire risk assessment]] · [[Quantitative risk assessment|Quantitative risk assessment (QRA)]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Explosions & Industrial Fires|Explosions & Industrial Fires]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Explosion]] · [[Hydrogen safety]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Firefighting & Fire Service|Firefighting & Fire Service]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Firefighting]] · [[Fire service access]]</div>
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<div style="font-size:0.96em; font-weight:bold;">[[:Category:Special Hazards & Building Types|Special Hazards & Building Types]]</div>
<div style="font-size:0.83em; line-height:1.7; margin-top:0.2em;">[[Lithium-ion battery fire]] · [[High-rise building]]</div>
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<h2 style="font-family:Arial,Helvetica,sans-serif; font-size:1.12em; font-weight:bold; color:#142B42; margin:0 0 0.4em; padding:0; border:0;">About this knowledge base</h2>
<p style="font-size:0.88em; margin:0;">The Fire Safety Academy Wiki connects fire science with engineering practice. Articles are organised by subject and written at four levels of depth, with references and links to related concepts.</p>
<p style="font-size:0.84em; color:#526475; margin:0.6em 0 0;">The wiki is growing. Red links mark pages that have not yet been created.</p>
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<div style="flex:1 1 200px; min-width:0; font-size:0.88em;">
<div style="font-weight:bold; margin-bottom:0.4em;">Keep exploring</div>
<ul style="margin:0 0 0 1.1em; padding:0;">
<li style="margin:0.3em 0;">[[Special:AllPages|All articles, A–Z]]</li>
<li style="margin:0.3em 0;">[[Special:Categories|Categories with articles]]</li>
<li style="margin:0.3em 0;">[[Special:RecentChanges|Recent changes]]</li>
<li style="margin:0.3em 0;">[[Talk:Main Page|Discuss this page]]</li>
</ul>
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