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A '''Fire extinguisher''' is a portable device containing a limited quantity of extinguishing agent for manual application to a fire. Its agent, discharge arrangement and tested use form a single unit. Selection depends on the fire class, fuel form, electrical condition, enclosure and compatibility of the agent with the hazard.<ref name="NUREG-F25">U.S. Nuclear Regulatory Commission (2005), pp. F-25–F-26.</ref><ref name="NUREG-B16">U.S. Nuclear Regulatory Commission (2005), p. B-16.</ref>
A '''fire extinguisher''' is a portable device, carried by hand or on wheels, that holds a limited supply of extinguishing agent for attacking a fire while it is still small.<ref name="SH126">Scheffey and Hickey (2002), p. 4-126.</ref><ref name="G155">Grant (2002), p. 4-155.</ref> Extinguishers contain water, foam, dry chemical powder, carbon dioxide, wet chemical solutions or halon. Each [[Extinguishing agent]] works in its own way and suits some fires better than others.<ref name="ISB15">Iqbal and Salley (2004), p. B-15.</ref><ref name="ISB16">Iqbal and Salley (2004), p. B-16.</ref> In the United States, the rating on an extinguisher combines a number for its relative effectiveness with letters for the [[Fire classes]] on which it was found to be effective.<ref name="ISF25">Iqbal and Salley (2004), p. F-25.</ref>


Extinguishers can apply water, foam, dry chemicals, wet chemicals or gaseous agents through different mechanisms. No extinguisher is suitable for every fire, and a matching class label alone does not guarantee successful extinction. Delivery, fire geometry, agent losses and re-ignition must also be considered.<ref name="NUREG-B15">U.S. Nuclear Regulatory Commission (2005), p. B-15.</ref><ref name="Scheffey-4-88">Scheffey (2002), p. 4-88.</ref>
Extinguishers belong to manual fire suppression, which people carry out with portable extinguishers, hoses or manually operated fixed systems.<ref name="ISF29">Iqbal and Salley (2004), p. F-29.</ref> A report of the US Nuclear Regulatory Commission describes a fire in its earliest stage as one that portable extinguishers or small hoses can still control without protective clothing or breathing apparatus.<ref name="ISF38">Iqbal and Salley (2004), p. F-38.</ref> Incident reviews describe fires that defeated several extinguishers but were then put out quickly with water.<ref name="ISH21">Iqbal and Salley (2004), p. H-21.</ref><ref name="ISH29">Iqbal and Salley (2004), pp. H-29–H-30.</ref> Fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they are specially trained.<ref name="IFEG177">National Research Council of Canada et al. (2005), p. 1.7-7.</ref>


Manual use also has operational consequences. Discharge can reduce visibility, alter breathing conditions, damage sensitive equipment or create chemical and electrical hazards. Those effects should be assessed alongside initial flame control and the ability to notify others and reach safety.<ref name="NUREG-B57">U.S. Nuclear Regulatory Commission (2005), p. B-57.</ref><ref name="NUREG-H29">U.S. Nuclear Regulatory Commission (2005), p. H-29.</ref>
== How an extinguisher works ==


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


Portable extinguishers provide a manually operated source of suppression before or alongside other measures. NUREG-1805 describes manual suppression as using hoses, portable extinguishers or manually actuated fixed systems by personnel. It differs from automatic fixed protection, which actuates without requiring someone to operate the outlet.<ref name="NUREG-F25" />
Sizes vary widely. Aqueous film-forming foam extinguishers are usually available as hand-portable models of 9 litres and as wheeled models holding 125 litres.<ref name="SH126" /> The supply of agent is limited. At one US nuclear power plant, three portable extinguishers together discharged about 32 kg (70 pounds) of dry chemical on a small fire of rags and debris.<ref name="ISH29" />


The extinguisher is part of a wider response, not an isolated guarantee of safety. Fire detection, warning, evacuation, firefighting access and water supplies may also be needed. A small initial agent supply cannot substitute for every one of those functions.<ref name="NUREG-F25" /><ref name="CVM2-53">Ministry of Business, Innovation and Employment (2025), p. 53.</ref>
The technology has changed over time. Carbon tetrachloride became available as early as 1907 and was used mostly in hand-pump portable extinguishers, because it conducted little electricity and left no residue. It caused a number of accidental deaths and serious injuries through its toxicity, and its use was halted during the 1950s.<ref name="G150">Grant (2002), p. 4-150.</ref> Methyl bromide, which was found in the late 1920s to be more effective than carbon tetrachloride, was never used in portable extinguishers because of its high toxicity.<ref name="G150" />


A person's decision to use an extinguisher depends on perceived conditions and available information. Bryan reports that occupants can choose between actions such as warning others, obtaining refuge, fighting the fire or evacuating. Those decisions can change as new cues appear.<ref name="Bryan-3-318">Bryan (2002), pp. 3-318–3-319.</ref>
Chemical foam extinguishers, in which a reaction between sodium bicarbonate and aluminium sulphate produced the foam and pushed it out, are now generally regarded as obsolete. Their manufacture in the United States stopped in 1969, and the National Fire Protection Association (NFPA) recommends replacing them.<ref name="ISB63">Iqbal and Salley (2004), p. B-63.</ref><ref name="SH126" /> The US Army also introduced portable extinguishers with halon 1301. Under the Montreal Protocol, however, the production of halons in the developed countries ended on 31 December 1993.<ref name="G151">Grant (2002), p. 4-151.</ref><ref name="DN173">DiNenno (2002), p. 4-173.</ref>


Training affects whether the agent and notification procedures are used appropriately. NUREG's description of fire-watch duties includes identifying hazards, using extinguishers and following proper notification procedures. The equipment must be supported by people who understand its intended use.<ref name="NUREG-F29">U.S. Nuclear Regulatory Commission (2005), p. F-29.</ref>
== Agents and what they do ==


Manual application can be appropriate for an incipient fire, but a developed fire presents a different problem. The quantity of agent, exposure conditions and ability to maintain a safe route must be evaluated. A class label does not make every manual attack reasonable or effective.<ref name="NUREG-B16" /><ref name="Bryan-3-318" />
NUREG-1805, a report of the US Nuclear Regulatory Commission, names four ways to put out a fire. They are separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or flame, and adding chemicals that change the combustion chemistry. More often several of these act at once.<ref name="ISB15" /> Water cools a burning solid, so that it gives off less flammable gas, and cools the flame.<ref name="ISB15" /> It is the most commonly used extinguishing agent, mainly because it is widely available and inexpensive and absorbs a great deal of heat as it turns into steam.<ref name="FL72">Fleming (2002), p. 4-72.</ref>
[[File:fse-fire-extinguisher-v1.svg|thumb|upright=1.5|alt=Portable agents cool, blanket, coat, inhibit chemistry or reduce oxygen.|Portable extinguishers use several different extinguishing mechanisms. Based on Iqbal and Salley (2004), pp. B-15–B-16.]]


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


An [[Extinguishing agent]] can separate fuel from flame, dilute oxygen, reduce temperature or modify combustion chemistry. Many agents combine those actions. Their relative importance changes with the fuel, enclosure and method of delivery.<ref name="NUREG-B15" />
Dry chemical powders are very common in manual extinguishers, and their most common use is on relatively small flammable liquid fires.<ref name="ISB56">Iqbal and Salley (2004), p. B-56.</ref> Common types include sodium bicarbonate, potassium bicarbonate and monoammonium phosphate, which is known as "ABC" or multipurpose powder.<ref name="ISB55" /> The powders probably act mainly by removing reactive chemical species from the flame, and they also absorb heat and block radiation.<ref name="ISB56" /> Monoammonium phosphate also forms a glassy coating over the burning surface, which makes it the only common powder considered effective against deep-seated fires.<ref name="ISB56" />


Water cools the solid and flame, reducing pyrolysis and heat feedback. Steam can impede oxygen in some confined conditions, while fog can reduce radiant transfer. Water nevertheless has compatibility limits for reactive materials, hot oils and energised equipment.<ref name="NUREG-B15" /><ref name="Fleming-4-72">Fleming (2002), p. 4-72.</ref>
Carbon dioxide is an electrically non-conductive inert gas that is suitable for Class B and Class C fires. It puts out a fire by lowering the concentration of oxygen, of fuel vapour or of both until combustion stops.<ref name="ISF12">Iqbal and Salley (2004), p. F-12.</ref> It has a long history as an extinguishing agent, mainly for flammable liquid fires and fires in electrical equipment.<ref name="ISB41" /> Wet chemical agents, solutions of water with potassium carbonate, potassium acetate or potassium citrate, are listed in NUREG-1805 for cooking oil and fat fires.<ref name="ISF70">Iqbal and Salley (2004), p. F-70.</ref><ref name="ISB16" />


[[Firefighting foam]] provides a surface blanket that restricts vapour release and air contact. It can also cool and, for some formulations, form a vapour-sealing film. Foam is water based and shares water-related electrical and reactive-material concerns.<ref name="Scheffey-4-88" /><ref name="NUREG-B60">U.S. Nuclear Regulatory Commission (2005), p. B-60.</ref>
== Classes and ratings ==


Dry chemicals can inhibit flame chemistry, absorb heat, block radiation and coat surfaces. Their performance depends on chemical formulation and particle size, and discharge can create a large contaminated area. Cleanup and corrosion can be significant after use.<ref name="NUREG-B55">U.S. Nuclear Regulatory Commission (2005), pp. B-55–B-56.</ref><ref name="NUREG-H29" />
The fire classes used in the United States come from NFPA 10, Standard for Portable Fire Extinguishers. Its 2002 edition, as summarised in NUREG-1805, has five classes. Class A covers ordinary combustibles such as wood, paper and many plastics, Class B flammable liquids and gases, and Class C energised electrical equipment. Class D covers combustible metals, and Class K cooking appliances with vegetable or animal oils and fats.<ref name="NFPA10">National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-13.</ref> The halon chapter of the SFPE Handbook of Fire Protection Engineering (third edition, 2002) shows only four classes, A to D, so the letters depend on the document and its edition.<ref name="G153">Grant (2002), p. 4-153.</ref>


Gaseous agents can interrupt flame chemistry or reduce oxygen without leaving powder residue. Enclosure openings and ventilation can reduce their effectiveness, and deep-seated combustion can continue after flames disappear. Retention and re-ignition require attention.<ref name="NUREG-B44">U.S. Nuclear Regulatory Commission (2005), pp. B-43–B-44.</ref>
The rating number shows relative effectiveness, and the letters show the classes of fire on which the extinguisher has been found to be effective.<ref name="ISF25" /> Ratings are based on standardised tests developed by Underwriters Laboratories.<ref name="ISF23">Iqbal and Salley (2004), p. F-23.</ref> A hand-portable foam extinguisher of 9 litres, for example, is rated 3A:20B, and a wheeled unit of 125 litres is rated 20A:160B.<ref name="SH126" /> For Class C the rating reflects the non-conductive properties of the agent. Once electrical equipment has been de-energised, extinguishers designed for Class A or Class B fires can be used safely.<ref name="ISB16" /><ref name="NFPA10" />


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


[[Fire classes]] group fuels and hazards to support selection, but their letters vary between systems. NUREG-1805 reproduces US A, B, C, D and K classes. Those labels should not be replaced with an assumed global classification.<ref name="NUREG-B16" />
== Role in fire protection ==


For ordinary combustibles, water and some foams or dry chemicals can cool and cover the fuel. Deep-seated material can continue to glow after visible flame disappears. Inspection for residual heat and re-ignition remains part of the manual operation.<ref name="NUREG-B16" /><ref name="NUREG-B56">U.S. Nuclear Regulatory Commission (2005), p. B-56.</ref>
Portable extinguishers are one layer among several. The US Nuclear Regulatory Commission's defence-in-depth approach aims to prevent fires, to detect, control and extinguish quickly those that do occur, and to protect safety functions if a fire is not put out promptly.<ref name="IS12">Iqbal and Salley (2004), p. 1-2.</ref> Portable extinguishers form part of the second layer, together with detectors, fixed suppression systems, hose stations, hydrants and fire brigades. The approach recognises that the first two layers are not always entirely successful.<ref name="IS12" />


For flammable liquids, the surface shape matters. Foam can cover a suitable pool, but plain water can allow an immiscible liquid to float and keep burning. Running fuel and pressurised sprays require different application evidence from a two-dimensional pool.<ref name="Fleming-4-72" /><ref name="Scheffey-4-88" />
In the same handbook, Grant gives an example for a computer room in which each stage of a fire has its own control measure. Portable extinguishers, together with an automatic halon system, serve the incipient stage, while automatic sprinklers serve the stage before flashover.<ref name="G155" /> A US fire risk method for nuclear power plants similarly notes that small fires are likely to be put out immediately with portable extinguishers.<ref name="NW1117">Nowlen et al. (2005b), p. 11-17.</ref> A fire has moved beyond this early stage when firefighters need thermal protective clothing or breathing apparatus, or have to crawl to stay below the smoke and heat.<ref name="ISF38" />


For energised equipment, conductivity and electrical exposure must be assessed. Dry chemicals can avoid electric shock in the cited guidance but can damage electronics. If power is isolated, the remaining fuels still require evaluation.<ref name="NUREG-B16" /><ref name="NUREG-B56" />
Extinguishers and an automatic [[Sprinkler system]] complement each other. NUREG-1805 notes that human response, such as discovering the fire and the travel of a fire brigade, usually takes much longer than the time sprinklers need to control a fire in its early stages.<ref name="IS101">Iqbal and Salley (2004), p. 10-1.</ref> In its study of the World Trade Center, the US National Institute of Standards and Technology (NIST) noted that the sprinklers there were designed to control fires. Manual intervention with hand-held extinguishers or hose lines was generally needed to put out all of the burning, especially in areas shielded from the sprinkler spray.<ref name="EV9">Evans et al. (2005), p. 9.</ref>


For combustible metals and hot cooking oils, compatibility is especially restrictive. NUREG-1805 warns against water-based agents for its Class D table and describes steam-driven ejection from hot oil. The correct agent must be identified by its tested purpose rather than general familiarity.<ref name="NUREG-B16" /><ref name="NUREG-B58">U.S. Nuclear Regulatory Commission (2005), pp. B-57–B-58.</ref>
In fire engineering design, the International Fire Engineering Guidelines (2005 edition) count manual suppression equipment among the measures for detection, warning and suppression.<ref name="IFEG1210">National Research Council of Canada et al. (2005), p. 1.2-10.</ref> Suppression by building occupants, using extinguishers and [[Hose reel|hose reels]], may be taken into account if appropriate criteria are used.<ref name="IFEG171">National Research Council of Canada et al. (2005), p. 1.7-1.</ref> The guidelines add that it is customary to assume that occupants will not engage in effective firefighting unless they belong to a specially trained site emergency response crew.<ref name="IFEG177" /> Professional [[Firefighting]] by the fire service is treated separately.<ref name="IFEG177" />


== Delivery and application limits ==
== People and training ==


A portable device contains a finite agent supply. Its effective discharge must reach the burning region in a useful form and remain long enough to control the fire. Agent expelled into the wrong region does not establish adequate protection, regardless of its chemical suitability.<ref name="Scheffey-4-88" /><ref name="NUREG-B60" />
Whether an extinguisher is used depends on the people present. In the SFPE Handbook, Bryan describes how a person who has recognised a fire evaluates the threat. The person then either evacuates the building or fights the fire, for example by fetching an extinguisher or operating a manual fire alarm.<ref name="BR318">Bryan (2002), pp. 3-318–3-319.</ref> People with firefighting training or experience, in surroundings they know, are likely to choose more adaptive actions. In one office building fire, regular occupants fought the fire and alerted others, while visitors attending training sessions mostly evacuated.<ref name="BR318" />


Foam requires correct proportioning, generation and distribution before it reaches the fuel. A blanket can be destroyed by heat, mechanical action, chemical incompatibility and rising combustion gases. Application must compensate for those losses while retaining a residual layer.<ref name="NUREG-B59">U.S. Nuclear Regulatory Commission (2005), pp. B-58–B-59.</ref>
Studies of residential and other fires give an idea of how often people fight fires. In a British study of 2,193 people in 952 fires, 14.7 percent showed firefighting behaviour, against 22.9 percent of 584 people in 335 mainly residential fires in a US study.<ref name="BR322">Bryan (2002), pp. 3-322–3-323.</ref> In the US study, fetching an extinguisher was the first action of 4.6 percent of the participants.<ref name="BR322" />


Dry chemicals need particles small enough to work in the flame but large enough to disperse effectively. The source describes coatings that reduce caking and a gas used to project the powder. Particle properties and discharge therefore affect performance as well as formulation.<ref name="NUREG-B55" />
In US nuclear power plants, a fire watch is a person who provides extra cover, for example during hot work, or makes up for an impaired fire protection system. Fire watches should be trained to recognise fire hazards, to use fire extinguishers and to follow notification procedures.<ref name="ISF29" /> A US method for counting fire events treats a fire as potentially challenging when a hose stream, several portable extinguishers or a fixed suppression system were needed.<ref name="NWC9">Nowlen et al. (2005b), pp. C-8–C-9.</ref> A hot-work fire also counts if active intervention was needed, even when the fire watch put it out quickly, although the use of a single extinguisher should not be the only indicator.<ref name="NWC9" />


Gaseous agents can distribute through an enclosure but escape through leakage and ventilation. Surface flame may disappear while interior material remains hot. Renewed air can then support re-ignition, so surface appearance alone is not a reliable endpoint.<ref name="NUREG-B44" />
== Requirements and maintenance ==


Water-based agents can also fail to reach shielded or deep-seated fuel. The fire may be controlled at the surface while continuing internally. A complete assessment includes what the agent actually contacts and what remains afterwards.<ref name="NUREG-B44" /><ref name="NUREG-B56" />
Requirements for extinguishers depend on the code or standard that applies and on its edition. In the United States, NUREG-1805 lists NFPA 10, Standard for Portable Fire Extinguishers (2002 edition), among the current NFPA standards. It notes that NFPA codes are revised on cycles of 3 to 5 years, so the edition in force at the time of design is the code of record.<ref name="ISE1">Iqbal and Salley (2004), p. E-1.</ref> The SFPE Handbook refers to NFPA 10 for the selection and placement of portable extinguishers.<ref name="SH126" /> Citing NFPA 10 and a handbook chapter on extinguisher use and maintenance, NUREG-1805 describes three hazard levels by the amount of Class A and B materials present. Light hazard can include offices and classrooms, ordinary hazard shops and parking garages, and extra hazard woodworking, vehicle repair and cooking areas.<ref name="ISB14">Conroy (1997) and National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-14.</ref>


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


Dry powder discharge can produce temporary breathing difficulty and reduced visibility. These effects are especially important in enclosed spaces. The agent may be described as generally nontoxic in the source while still creating an immediate operational hazard.<ref name="NUREG-B57" /><ref name="NUREG-H29" />
Maintenance is part of [[Fire safety management]]. The International Fire Engineering Guidelines state that active fire protection equipment, including suppression equipment, needs particular attention to ensure proper installation, commissioning, management and use. Its maintenance should follow the relevant codes, standards and manufacturer's literature.<ref name="IFEG178">National Research Council of Canada et al. (2005), p. 1.7-8.</ref> The New Zealand part of the guidelines adds that the fire safety of a building depends on the ongoing functioning of its fire safety system. Inspection, testing and maintenance programmes should therefore have due regard to New Zealand standards and legislation.<ref name="IFEGNZ">National Research Council of Canada et al. (2005), p. 0.3-8 (Part 0, New Zealand).</ref> Among the information notices of the Nuclear Regulatory Commission listed in NUREG-1805 is one of 11 April 2001 titled "Neglected Fire Extinguisher Maintenance Causes Fatality".<ref name="ISD14">Iqbal and Salley (2004), p. D-14.</ref>


Residue can be difficult to remove and can corrode sensitive equipment. NUREG-1805 highlights the acidic nature of monoammonium phosphate and its affinity for water. Applying water during cleanup can accelerate corrosion, so the agent's chemical behaviour continues after suppression.<ref name="NUREG-H29" />
== Limits, side effects and incident experience ==


A Point Beach case in NUREG-1805 illustrates these consequences. Three portable dry-chemical extinguishers were used before a hose line with water finally extinguished the fire after earlier reflash. White residue spread over building surfaces, showing that agent quantity and cleanup belong in selection.<ref name="NUREG-H29" />
Dry chemical powder has side effects. Its sudden release and unexpected re-ignition of the fire are hazards, and although the powders are non-toxic, they can cause temporary breathing difficulty and reduce visibility.<ref name="ISB57">Iqbal and Salley (2004), p. B-57.</ref> All powders need significant cleaning after use, and some corrosion or damage is possible.<ref name="ISB56" /> Powders become sticky when heated, and applying water to the residue speeds up the corrosion of equipment.<ref name="ISH29" />


Water and foam can react with particular materials or energised equipment. Hot oil can turn water to steam and eject burning liquid, while some reactive substances can generate heat or hazardous gases. Compatibility must be established before manual application.<ref name="Fleming-4-72" /><ref name="NUREG-B60" />
At the Point Beach 1 nuclear power plant in 2001, three portable dry chemical extinguishers failed to put out a small fire, which re-ignited twice. The fire brigade then put it out easily with about 57 to 76 litres (15 to 20 gallons) of water from a hose line.<ref name="ISH29" /> White powder covered about half of the containment basement floor, and NUREG-1805 concludes that the cleanup effort called for a more careful choice of extinguishing agent.<ref name="ISH29" />
[[File:fse-fire-extinguisher-v3.svg|thumb|upright=1.5|alt=Powder clouds reduce visibility, coat equipment and require cleanup while hot fuel can reflash.|Extinguishing also creates post-discharge hazards and restoration needs. Based on Iqbal and Salley (2004), pp. H-29–H-30.]]


Gaseous agents can change the enclosure atmosphere, and historical Halon references do not establish current acceptability. Human exposure, agent decomposition and environmental requirements must be evaluated for the particular product and jurisdiction. The absence of residue does not imply absence of hazard.<ref name="NUREG-B41">U.S. Nuclear Regulatory Commission (2005), p. B-41.</ref><ref name="NUREG-B43">U.S. Nuclear Regulatory Commission (2005), p. B-43.</ref>
Fires in energised electrical equipment have repeatedly defeated portable extinguishers in US nuclear power plants. At Waterford 3 in 1995, attacks with carbon dioxide, halon and dry chemical extinguishers failed. Water was permitted only about 90 minutes after the fire started, and the fire was then under control within 4 minutes.<ref name="ISH21" /> At Prairie Island 1 in 2001, more than 20 portable carbon dioxide extinguishers were used over about 1.5 hours on a breaker fire, and two fire brigade members were treated for heat exhaustion.<ref name="ISH30">Iqbal and Salley (2004), pp. H-30–H-31.</ref> A review of high-energy arcing faults in electrical switchgear notes that in severe events the first extinguishers may be ineffective whatever the agent, and that such fires were finally put out with water.<ref name="NWM3">Nowlen et al. (2005b), p. M-3.</ref>


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


A [[Hose reel]] provides another manual water-delivery arrangement, connected to a supply rather than relying only on stored agent in a portable cylinder. It changes quantity, reach and water-supply dependencies. Those differences should be considered when selecting manual provisions.<ref name="NUREG-F61">U.S. Nuclear Regulatory Commission (2005), pp. F-61–F-62.</ref><ref name="NUREG-F25" />
Gaseous agents also have hazards of their own. [[Carbon dioxide]] replaces the oxygen in the air, and people become unconscious at a concentration of 10 percent by volume.<ref name="ISB41" /> Grant notes that the high concentrations needed to extinguish a fire with carbon dioxide make the protected space lethal to people.<ref name="G155" /> In battery rooms with lead-acid batteries, NUREG-1805 advises against discharging an extinguisher directly onto a battery, because the thermal shock may crack its case or cover.<ref name="IS1611">Iqbal and Salley (2004), p. 16-11.</ref>
 
Fixed suppression can act automatically and does not depend on someone reaching the fire with an extinguisher. Sprinklers, for example, open in response to heat and deliver water through a fixed network. Their availability still depends on valves, water supply, maintenance and the protected hazard.<ref name="NUREG-10-1">U.S. Nuclear Regulatory Commission (2005), pp. 10-1–10-2.</ref>
 
Manual and automatic measures can complement each other. Automatic systems can begin control early, while trained personnel provide additional suppression, notification and inspection. The complete response should not assume that either approach removes every failure path.<ref name="NUREG-10-1" /><ref name="NUREG-F25" />
 
Fire department access and water delivery become more important as an incident develops. C/VM2's firefighting scenario addresses vehicle access, water delivery, information and safe working conditions. A portable extinguisher cannot substitute for those operational provisions.<ref name="CVM2-53" />
 
The protected fuel and building layout affect which manual provisions are practical. Access to the fire, available exits, visibility and agent delivery must be evaluated. Selecting equipment without considering those conditions can leave an unusable provision.<ref name="Bryan-3-318" /><ref name="CVM2-53" />
 
== Management and maintenance ==
 
[[Fire safety management]] must preserve the extinguisher's intended function and compatibility. This includes keeping the selected agent and unit suitable for the current hazards. Changes in fuel, equipment or occupancy can make the original choice inappropriate.<ref name="IFEG-0-3-8">Australian Building Codes Board et al. (2005), p. 0.3-8.</ref><ref name="NUREG-B16" />
 
Inspection should confirm that the correct unit remains available and that its intended use is clear. A device present in a cabinet but incompatible with the hazard does not provide the expected protection. Inspection should also cover accessibility and any conditions that could prevent manual use.<ref name="IFEG-1-8-14">Australian Building Codes Board et al. (2005), pp. 1.8-13–1.8-14.</ref><ref name="NUREG-F29" />
 
Maintenance requirements should come from the applicable standard, manufacturer and jurisdiction. NUREG-1805 lists NFPA 10 as the US portable-extinguisher standard in its historical context, but it does not provide a universal service schedule. That schedule must not be invented from the general concept.<ref name="NUREG-E1">U.S. Nuclear Regulatory Commission (2005), p. E-1.</ref>
 
Training should address agent selection, limitations and notification. Fire-watch guidance in NUREG-1805 links extinguisher use with hazard recognition and proper notification. People expected to respond should understand those procedures before an incident.<ref name="NUREG-F29" />
 
Post-use review should consider residue, re-ignition and restoration. Spent or discharged equipment may no longer provide its intended protection, and the area may require cleanup or further assessment. The incident response is incomplete until those conditions are addressed.<ref name="NUREG-H29" /><ref name="IFEG-1-8-14" />
 
== Evaluation and common misunderstandings ==
 
A portable extinguisher is not automatically the safest or most effective response for every fire. Its usefulness depends on fire development, fuel, agent and the conditions faced by the person using it. Those conditions must be assessed instead of relying on the class label alone.<ref name="Bryan-3-318" /><ref name="NUREG-B16" />
 
More agent is not always better. Excess discharge can increase contamination, visibility loss and cleanup, while the fire may continue because of poor delivery or re-ignition. The Point Beach example shows that repeated discharge does not necessarily resolve the underlying problem.<ref name="NUREG-H29" />
 
Nonconductive does not mean harmless. An agent may avoid electrical shock but still damage electronics or create breathing and visibility hazards. Equipment protection and human exposure must be included in compatibility assessment.<ref name="NUREG-B56" /><ref name="NUREG-B57" />
 
No residue does not mean no hazard. Gaseous agents can alter the enclosure atmosphere and may not be retained long enough to prevent re-ignition. Enclosure conditions and occupancy remain part of the evaluation.<ref name="NUREG-B44" /><ref name="NUREG-B41" />
 
The complete extinguisher assessment therefore includes the unit, the fire, the person and the building. It covers selection, manual delivery, secondary effects, subsequent fire behaviour and management. Those linked considerations determine whether the portable device provides useful protection.<ref name="NUREG-F25" /><ref name="IFEG-1-8-14" />
 
[[Firefighting]] covers the wider activities used to control and extinguish fires, including manual suppression, fixed systems, access and water delivery. A portable extinguisher is only one possible component of that wider response. Its limitations should therefore be represented in the building's fire-safety and emergency arrangements.<ref name="NUREG-F25" /><ref name="CVM2-53" />
 
The selection record should identify the hazard addressed by each unit. Fuel form, electrical condition, enclosure and nearby sensitive equipment can all change the appropriate choice. Recording those conditions makes later substitution or occupancy review more reliable than an inventory containing only cylinder locations.<ref name="NUREG-B16" /><ref name="IFEG-0-3-8" />
 
Operational planning should distinguish portable-agent readiness from other dependencies. An extinguisher may be fully charged but unsuitable for the fire, just as a hose or fixed system may be unavailable because its supply is impaired. Each provision needs its own functional and compatibility check.<ref name="NUREG-10-1" /><ref name="NUREG-F25" />
 
Historical fire reports should be interpreted with the agent and circumstances retained. The Point Beach case does not show that every dry-chemical extinguisher is ineffective, but it does show repeated reflash, difficult cleanup and the consequences of a poor match between agent and situation. Those details are more instructive than a generic success-or-failure label.<ref name="NUREG-H29" />
 
Commissioning and drills should examine the complete intended response. Occupants need intelligible warning and a usable route, while personnel expected to use extinguishers need appropriate knowledge of agent limitations and notification. The presence of portable equipment does not demonstrate those behavioural and organisational conditions.<ref name="NUREG-F29" /><ref name="Proulx-3-350">Proulx (2002), p. 3-350.</ref>
 
After an incident, the area should be assessed for remaining combustion, contamination and impaired protection. Dry powder may require specialised cleanup, while hot fuel can support renewed burning. The provision for the next response should not be assumed until those conditions and the unit's readiness have been reviewed. Any remaining hazards and impaired provisions should be documented for the responsible personnel.<ref name="NUREG-H29" /><ref name="NUREG-B44" />


== See also ==
== See also ==


* [[Extinguishing agent]]
* [[Fire classes]]
* [[Hot work]]
* [[Hot work]]
* [[Dry and wet risers]]
* [[Fire hydrant]]


== Notes ==
== Notes ==
Line 125: Line 84:
== 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.
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 3-315–3-341). National Fire Protection Association; Society of Fire Protection Engineers.
* Bryan, J. L. (2002). Behavioral response to fire and smoke. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* DiNenno, P. J. (2002). Halon replacement clean agent total flooding systems. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-173–4-200). National Fire Protection Association; Society of Fire Protection Engineers.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Evans, D. D., Peacock, R. D., Kuligowski, E. D., Dols, W. S., & Grosshandler, W. L. (2005). ''Active fire protection systems'' (NIST NCSTAR 1-4). National Institute of Standards and Technology.
* Ministry of Business, Innovation and Employment. (2025). ''C protection from fire: Verification method C/VM2'' (2nd ed.). New Zealand Government.
* Fleming, R. P. (2002). Automatic sprinkler system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-72–4-87). National Fire Protection Association; Society of Fire Protection Engineers.
* Proulx, G. (2002). Movement of people: The evacuation timing. 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, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-149–4-172). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno (Ed.), ''SFPE handbook of fire protection engineering'' (3rd ed.). National Fire Protection Association.
* Grill, R. A., & Johnson, D. A. (2005c). ''Post-construction modifications to fire protection and life safety systems of the World Trade Center towers'' (NIST NCSTAR 1-1H). National Institute of Standards and Technology.
* 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). Author.
* Iqbal, N., & Salley, M. H. (2004). ''Fire Dynamics Tools (FDTs): Quantitative fire hazard analysis methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program'' (NUREG-1805). U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation.
* Lew, H. S., Bukowski, R. W., & Carino, N. J. (2005). ''Design, construction, and maintenance of structural and life safety systems'' (NIST NCSTAR 1-1). National Institute of Standards and Technology.
* National Research Council of Canada, International Code Council, Department of Building and Housing, & Australian Building Codes Board. (2005). ''International fire engineering guidelines'' (2005 ed.). Australian Building Codes Board.
* Nowlen, S. P., Najafi, B., Wyant, F. J., Forester, J., Kazarians, M., Kolaczkowski, A., Joglar, F., Funk, D., Hannaman, G., & Anoba, R. (2005b). ''EPRI/NRC-RES fire PRA methodology for nuclear power facilities: Vol. 2. Detailed methodology'' (NUREG/CR-6850; EPRI 1011989). Electric Power Research Institute; U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research.
* Scheffey, J. L. (2002). Foam agents and AFFF system design considerations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-88–4-122). National Fire Protection Association; Society of Fire Protection Engineers.
* Scheffey, J. L., & Hickey, H. E. (2002). Foam system calculations. In P. J. DiNenno, D. Drysdale, C. L. Beyler, W. D. Walton, R. L. P. Custer, J. R. Hall Jr., & J. M. Watts Jr. (Eds.), ''SFPE handbook of fire protection engineering'' (3rd ed., pp. 4-123–4-148). National Fire Protection Association; Society of Fire Protection Engineers.


[[Category:Firefighting & Fire Service]]
[[Category:Firefighting & Fire Service]]

Latest revision as of 19:35, 2 November 2026

A fire extinguisher is a portable device, carried by hand or on wheels, that holds a limited supply of extinguishing agent for attacking a fire while it is still small.[1][2] Extinguishers contain water, foam, dry chemical powder, carbon dioxide, wet chemical solutions or halon. Each Extinguishing agent works in its own way and suits some fires better than others.[3][4] In the United States, the rating on an extinguisher combines a number for its relative effectiveness with letters for the Fire classes on which it was found to be effective.[5]

Extinguishers belong to manual fire suppression, which people carry out with portable extinguishers, hoses or manually operated fixed systems.[6] A report of the US Nuclear Regulatory Commission describes a fire in its earliest stage as one that portable extinguishers or small hoses can still control without protective clothing or breathing apparatus.[7] Incident reviews describe fires that defeated several extinguishers but were then put out quickly with water.[8][9] Fire engineering analyses customarily assume that occupants will not fight a fire effectively unless they are specially trained.[10]

How an extinguisher works

An extinguisher stores its agent under pressure, or together with a gas that drives it out. Dry chemical powder consists of fine particles coated to prevent caking, and an inert gas projects the powder onto the fire.[11] Carbon dioxide is stored as a gas liquefied under pressure and provides its own pressure for release.[12] A portable extinguisher with aqueous film-forming foam closely resembles a stored-pressure water extinguisher, except for its special nozzle.[1]

Sizes vary widely. Aqueous film-forming foam extinguishers are usually available as hand-portable models of 9 litres and as wheeled models holding 125 litres.[1] The supply of agent is limited. At one US nuclear power plant, three portable extinguishers together discharged about 32 kg (70 pounds) of dry chemical on a small fire of rags and debris.[9]

The technology has changed over time. Carbon tetrachloride became available as early as 1907 and was used mostly in hand-pump portable extinguishers, because it conducted little electricity and left no residue. It caused a number of accidental deaths and serious injuries through its toxicity, and its use was halted during the 1950s.[13] Methyl bromide, which was found in the late 1920s to be more effective than carbon tetrachloride, was never used in portable extinguishers because of its high toxicity.[13]

Chemical foam extinguishers, in which a reaction between sodium bicarbonate and aluminium sulphate produced the foam and pushed it out, are now generally regarded as obsolete. Their manufacture in the United States stopped in 1969, and the National Fire Protection Association (NFPA) recommends replacing them.[14][1] The US Army also introduced portable extinguishers with halon 1301. Under the Montreal Protocol, however, the production of halons in the developed countries ended on 31 December 1993.[15][16]

Agents and what they do

NUREG-1805, a report of the US Nuclear Regulatory Commission, names four ways to put out a fire. They are separating the fuel from the flame, removing or diluting the oxygen, cooling the fuel or flame, and adding chemicals that change the combustion chemistry. More often several of these act at once.[3] Water cools a burning solid, so that it gives off less flammable gas, and cools the flame.[3] It is the most commonly used extinguishing agent, mainly because it is widely available and inexpensive and absorbs a great deal of heat as it turns into steam.[17]

Portable agents cool, blanket, coat, inhibit chemistry or reduce oxygen.
Portable extinguishers use several different extinguishing mechanisms. Based on Iqbal and Salley (2004), pp. B-15–B-16.

Water also has clear limits. It is unsuitable for certain water-reactive materials, with which it can produce heat, flammable or toxic gases, or explosions.[17] Burning hydrocarbon fuels float on water and keep burning, and water under very hot oil turns to steam and throws out burning oil.[17][18] Firefighting foam overcomes the floating problem by forming a layer on the liquid that keeps out air and stops the fuel from evaporating.[19] Foam is water-based, however, so it shares the risk of electric shock from live equipment.[20]

Dry chemical powders are very common in manual extinguishers, and their most common use is on relatively small flammable liquid fires.[21] Common types include sodium bicarbonate, potassium bicarbonate and monoammonium phosphate, which is known as "ABC" or multipurpose powder.[11] The powders probably act mainly by removing reactive chemical species from the flame, and they also absorb heat and block radiation.[21] Monoammonium phosphate also forms a glassy coating over the burning surface, which makes it the only common powder considered effective against deep-seated fires.[21]

Carbon dioxide is an electrically non-conductive inert gas that is suitable for Class B and Class C fires. It puts out a fire by lowering the concentration of oxygen, of fuel vapour or of both until combustion stops.[22] It has a long history as an extinguishing agent, mainly for flammable liquid fires and fires in electrical equipment.[12] Wet chemical agents, solutions of water with potassium carbonate, potassium acetate or potassium citrate, are listed in NUREG-1805 for cooking oil and fat fires.[23][4]

Classes and ratings

The fire classes used in the United States come from NFPA 10, Standard for Portable Fire Extinguishers. Its 2002 edition, as summarised in NUREG-1805, has five classes. Class A covers ordinary combustibles such as wood, paper and many plastics, Class B flammable liquids and gases, and Class C energised electrical equipment. Class D covers combustible metals, and Class K cooking appliances with vegetable or animal oils and fats.[24] The halon chapter of the SFPE Handbook of Fire Protection Engineering (third edition, 2002) shows only four classes, A to D, so the letters depend on the document and its edition.[25]

The rating number shows relative effectiveness, and the letters show the classes of fire on which the extinguisher has been found to be effective.[5] Ratings are based on standardised tests developed by Underwriters Laboratories.[26] A hand-portable foam extinguisher of 9 litres, for example, is rated 3A:20B, and a wheeled unit of 125 litres is rated 20A:160B.[1] For Class C the rating reflects the non-conductive properties of the agent. Once electrical equipment has been de-energised, extinguishers designed for Class A or Class B fires can be used safely.[4][24]

The class table in NUREG-1805 shows why the letters matter. It states that water and water-based extinguishers should never be used on Class D metal fires, and that a Class D extinguisher must suppress the fire without reacting physically or chemically with the metal.[4] Among the powders, monoammonium phosphate is not recommended for kitchen fires involving hot fat because it is acidic; an alkaline powder such as potassium bicarbonate is preferred.[21]

Role in fire protection

Portable extinguishers are one layer among several. The US Nuclear Regulatory Commission's defence-in-depth approach aims to prevent fires, to detect, control and extinguish quickly those that do occur, and to protect safety functions if a fire is not put out promptly.[27] Portable extinguishers form part of the second layer, together with detectors, fixed suppression systems, hose stations, hydrants and fire brigades. The approach recognises that the first two layers are not always entirely successful.[27]

In the same handbook, Grant gives an example for a computer room in which each stage of a fire has its own control measure. Portable extinguishers, together with an automatic halon system, serve the incipient stage, while automatic sprinklers serve the stage before flashover.[2] A US fire risk method for nuclear power plants similarly notes that small fires are likely to be put out immediately with portable extinguishers.[28] A fire has moved beyond this early stage when firefighters need thermal protective clothing or breathing apparatus, or have to crawl to stay below the smoke and heat.[7]

Extinguishers and an automatic Sprinkler system complement each other. NUREG-1805 notes that human response, such as discovering the fire and the travel of a fire brigade, usually takes much longer than the time sprinklers need to control a fire in its early stages.[29] In its study of the World Trade Center, the US National Institute of Standards and Technology (NIST) noted that the sprinklers there were designed to control fires. Manual intervention with hand-held extinguishers or hose lines was generally needed to put out all of the burning, especially in areas shielded from the sprinkler spray.[30]

In fire engineering design, the International Fire Engineering Guidelines (2005 edition) count manual suppression equipment among the measures for detection, warning and suppression.[31] Suppression by building occupants, using extinguishers and hose reels, may be taken into account if appropriate criteria are used.[32] The guidelines add that it is customary to assume that occupants will not engage in effective firefighting unless they belong to a specially trained site emergency response crew.[10] Professional Firefighting by the fire service is treated separately.[10]

People and training

Whether an extinguisher is used depends on the people present. In the SFPE Handbook, Bryan describes how a person who has recognised a fire evaluates the threat. The person then either evacuates the building or fights the fire, for example by fetching an extinguisher or operating a manual fire alarm.[33] People with firefighting training or experience, in surroundings they know, are likely to choose more adaptive actions. In one office building fire, regular occupants fought the fire and alerted others, while visitors attending training sessions mostly evacuated.[33]

Studies of residential and other fires give an idea of how often people fight fires. In a British study of 2,193 people in 952 fires, 14.7 percent showed firefighting behaviour, against 22.9 percent of 584 people in 335 mainly residential fires in a US study.[34] In the US study, fetching an extinguisher was the first action of 4.6 percent of the participants.[34]

In US nuclear power plants, a fire watch is a person who provides extra cover, for example during hot work, or makes up for an impaired fire protection system. Fire watches should be trained to recognise fire hazards, to use fire extinguishers and to follow notification procedures.[6] A US method for counting fire events treats a fire as potentially challenging when a hose stream, several portable extinguishers or a fixed suppression system were needed.[35] A hot-work fire also counts if active intervention was needed, even when the fire watch put it out quickly, although the use of a single extinguisher should not be the only indicator.[35]

Requirements and maintenance

Requirements for extinguishers depend on the code or standard that applies and on its edition. In the United States, NUREG-1805 lists NFPA 10, Standard for Portable Fire Extinguishers (2002 edition), among the current NFPA standards. It notes that NFPA codes are revised on cycles of 3 to 5 years, so the edition in force at the time of design is the code of record.[36] The SFPE Handbook refers to NFPA 10 for the selection and placement of portable extinguishers.[1] Citing NFPA 10 and a handbook chapter on extinguisher use and maintenance, NUREG-1805 describes three hazard levels by the amount of Class A and B materials present. Light hazard can include offices and classrooms, ordinary hazard shops and parking garages, and extra hazard woodworking, vehicle repair and cooking areas.[37]

New York City shows how requirements can sit in different documents. NIST found that the 1968 New York City Building Code had no requirements for fire extinguishers, because it required occupant hose reels instead.[38] For the World Trade Center, the Port Authority nevertheless required portable extinguishers in all spaces. It followed a Fire Department of New York directive of 17 September 1980 and section 27-4009 of the New York City Fire Prevention Code of 1 July 1988.[39]

Maintenance is part of Fire safety management. The International Fire Engineering Guidelines state that active fire protection equipment, including suppression equipment, needs particular attention to ensure proper installation, commissioning, management and use. Its maintenance should follow the relevant codes, standards and manufacturer's literature.[40] The New Zealand part of the guidelines adds that the fire safety of a building depends on the ongoing functioning of its fire safety system. Inspection, testing and maintenance programmes should therefore have due regard to New Zealand standards and legislation.[41] Among the information notices of the Nuclear Regulatory Commission listed in NUREG-1805 is one of 11 April 2001 titled "Neglected Fire Extinguisher Maintenance Causes Fatality".[42]

Limits, side effects and incident experience

Dry chemical powder has side effects. Its sudden release and unexpected re-ignition of the fire are hazards, and although the powders are non-toxic, they can cause temporary breathing difficulty and reduce visibility.[43] All powders need significant cleaning after use, and some corrosion or damage is possible.[21] Powders become sticky when heated, and applying water to the residue speeds up the corrosion of equipment.[9]

At the Point Beach 1 nuclear power plant in 2001, three portable dry chemical extinguishers failed to put out a small fire, which re-ignited twice. The fire brigade then put it out easily with about 57 to 76 litres (15 to 20 gallons) of water from a hose line.[9] White powder covered about half of the containment basement floor, and NUREG-1805 concludes that the cleanup effort called for a more careful choice of extinguishing agent.[9]

Powder clouds reduce visibility, coat equipment and require cleanup while hot fuel can reflash.
Extinguishing also creates post-discharge hazards and restoration needs. Based on Iqbal and Salley (2004), pp. H-29–H-30.

Fires in energised electrical equipment have repeatedly defeated portable extinguishers in US nuclear power plants. At Waterford 3 in 1995, attacks with carbon dioxide, halon and dry chemical extinguishers failed. Water was permitted only about 90 minutes after the fire started, and the fire was then under control within 4 minutes.[8] At Prairie Island 1 in 2001, more than 20 portable carbon dioxide extinguishers were used over about 1.5 hours on a breaker fire, and two fire brigade members were treated for heat exhaustion.[44] A review of high-energy arcing faults in electrical switchgear notes that in severe events the first extinguishers may be ineffective whatever the agent, and that such fires were finally put out with water.[45]

Delivery is a further limit. In a deep-seated fire, Smouldering continues below the surface, where an agent cannot easily reach the seat of the fire.[46] A gaseous agent can put out the visible flames at once while glowing combustion continues inside, and the fire can then re-ignite when air returns.[47] Low-expansion foam works well on a flat pool fire but is not particularly effective on running fuel or a pressurised spray.[19]

Extinguisher discharge reaches a pool but leaves shielded and deep fuel hot.
Manual extinguishing depends on delivery, coverage and remaining fuel condition. Based on Scheffey (2002), p. 4-88 and Iqbal and Salley (2004), pp. B-43–B-44.

Gaseous agents also have hazards of their own. Carbon dioxide replaces the oxygen in the air, and people become unconscious at a concentration of 10 percent by volume.[12] Grant notes that the high concentrations needed to extinguish a fire with carbon dioxide make the protected space lethal to people.[2] In battery rooms with lead-acid batteries, NUREG-1805 advises against discharging an extinguisher directly onto a battery, because the thermal shock may crack its case or cover.[48]

See also

Notes

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Scheffey and Hickey (2002), p. 4-126.
  2. ↑ 2.0 2.1 2.2 Grant (2002), p. 4-155.
  3. ↑ 3.0 3.1 3.2 Iqbal and Salley (2004), p. B-15.
  4. ↑ 4.0 4.1 4.2 4.3 Iqbal and Salley (2004), p. B-16.
  5. ↑ 5.0 5.1 Iqbal and Salley (2004), p. F-25.
  6. ↑ 6.0 6.1 Iqbal and Salley (2004), p. F-29.
  7. ↑ 7.0 7.1 Iqbal and Salley (2004), p. F-38.
  8. ↑ 8.0 8.1 Iqbal and Salley (2004), p. H-21.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 Iqbal and Salley (2004), pp. H-29–H-30.
  10. ↑ 10.0 10.1 10.2 National Research Council of Canada et al. (2005), p. 1.7-7.
  11. ↑ 11.0 11.1 Iqbal and Salley (2004), p. B-55.
  12. ↑ 12.0 12.1 12.2 Iqbal and Salley (2004), p. B-41.
  13. ↑ 13.0 13.1 Grant (2002), p. 4-150.
  14. ↑ Iqbal and Salley (2004), p. B-63.
  15. ↑ Grant (2002), p. 4-151.
  16. ↑ DiNenno (2002), p. 4-173.
  17. ↑ 17.0 17.1 17.2 Fleming (2002), p. 4-72.
  18. ↑ Iqbal and Salley (2004), p. B-58.
  19. ↑ 19.0 19.1 Scheffey (2002), p. 4-88.
  20. ↑ Iqbal and Salley (2004), p. B-60.
  21. ↑ 21.0 21.1 21.2 21.3 21.4 Iqbal and Salley (2004), p. B-56.
  22. ↑ Iqbal and Salley (2004), p. F-12.
  23. ↑ Iqbal and Salley (2004), p. F-70.
  24. ↑ 24.0 24.1 National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-13.
  25. ↑ Grant (2002), p. 4-153.
  26. ↑ Iqbal and Salley (2004), p. F-23.
  27. ↑ 27.0 27.1 Iqbal and Salley (2004), p. 1-2.
  28. ↑ Nowlen et al. (2005b), p. 11-17.
  29. ↑ Iqbal and Salley (2004), p. 10-1.
  30. ↑ Evans et al. (2005), p. 9.
  31. ↑ National Research Council of Canada et al. (2005), p. 1.2-10.
  32. ↑ National Research Council of Canada et al. (2005), p. 1.7-1.
  33. ↑ 33.0 33.1 Bryan (2002), pp. 3-318–3-319.
  34. ↑ 34.0 34.1 Bryan (2002), pp. 3-322–3-323.
  35. ↑ 35.0 35.1 Nowlen et al. (2005b), pp. C-8–C-9.
  36. ↑ Iqbal and Salley (2004), p. E-1.
  37. ↑ Conroy (1997) and National Fire Protection Association (2002), as cited in Iqbal and Salley (2004), p. B-14.
  38. ↑ Lew et al. (2005), p. 151.
  39. ↑ Grill and Johnson (2005c), p. 17.
  40. ↑ National Research Council of Canada et al. (2005), p. 1.7-8.
  41. ↑ National Research Council of Canada et al. (2005), p. 0.3-8 (Part 0, New Zealand).
  42. ↑ Iqbal and Salley (2004), p. D-14.
  43. ↑ Iqbal and Salley (2004), p. B-57.
  44. ↑ Iqbal and Salley (2004), pp. H-30–H-31.
  45. ↑ Nowlen et al. (2005b), p. M-3.
  46. ↑ Iqbal and Salley (2004), pp. B-39–B-40.
  47. ↑ Iqbal and Salley (2004), p. B-43.
  48. ↑ Iqbal and Salley (2004), p. 16-11.

References

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