imported>Kovcszaln6: /* Combustible metals: Class D (US/EU/AU) */ when?

2025-06-12T15:26:20Z

Combustible metals: Class D (US/EU/AU): when?

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{{Short description|System of categorizing fire}}
{{Use mdy dates|date=March 2025}}

[[File:Grease Fire Demonstration for Fire Prevention Week (6394291).jpg|thumb|Demonstration of using the wrong suppressant on a grease fire]]
'''Fire classification''' is a system of categorizing [[fire]]s with regard to the type(s) of [[combustion|combustible]] material(s) involved, and the form(s) of suitable extinguishing agent(s).<ref name=":2">{{cite book | title=Fire Detection and Suppression Systems |edition=Third | publisher=International Fire Service Training Association | year=2005 | location=Stillwater, OK | page=9 | isbn=0-87939-267-3 |oclc=62785313}}</ref> Classes are often assigned letter designations,<ref name=":1">{{Cite web |date=February 15, 2025 |title=Understanding Various Types of Fires and Their Causes |url=https://kforcesecurity.co.uk/blog/types-of-fires/ |url-status=live |access-date=February 15, 2025 |website=KForce Security}}</ref> which can differ somewhat between territories.

== Standards ==
* [[International Organization for Standardization|International (ISO)]]: ISO3941 Classification of fires
* [[Australia]]: AS/NZS 1850
* [[Europe]]: DIN EN2 Classification of fires
* [[United States]]: NFPA 10 Chapter 5.2.1-5.2.5

==Materials and hazards==

=== Flammable solids: Class A (US/EU/AU) ===
[[File:Fire Combustible.png|left|60px]]
Fires involving ordinary flammable [[solid]]s fall under '''Class A'''. This includes [[wood]], [[paper]], [[fabric]], [[rubber]], and some types of [[plastic]]s. Such fires may be extinguished by water, wet chemical suppression, or dry chemical powder.<ref name=IFSTA-10>{{cite book | title=Fire Detection and Suppression Systems |edition=Third | publisher=International Fire Service Training Association | year=2005 | location=Stillwater, OK | page=10 | isbn=0-87939-267-3 |oclc=62785313}}</ref><ref name=":0">{{Cite web|url=https://www.usfa.fema.gov/prevention/outreach/extinguishers.html|title=Choosing and using fire extinguishers|date=December 12, 2017|website=U.S. Fire Administration|language=en|access-date=May 30, 2019|archive-date=May 30, 2019|archive-url=https://web.archive.org/web/20190530154609/https://www.usfa.fema.gov/prevention/outreach/extinguishers.html|url-status=dead}}</ref>
{{clear}}

=== Flammable liquids: Class B (US/EU/AU) ===
[[File:Fire Liquid.png|left|60px]]
[[File:Extincteur-p1010032.jpg|thumb|upright|A carbon dioxide [[fire extinguisher]] rated for flammable liquids and gases]]
Fires involving flammable [[liquid]]s or liquefiable solids fall under '''Class B'''{{efn-num|Under the European and Australian systems, flammable liquids designated Class B require flash points no more than {{Convert|93|°C|°F|abbr=on}}.<ref name=":6">{{cite web |author= |date=March 23, 2025 |title=Flammable and combustible liquids |url=https://www.worksafe.qld.gov.au/safety-and-prevention/hazards/hazardous-chemicals/specific-hazardous-chemicals/flammable-and-combustible-liquids#:~:text=The%20globally%20harmonised%20system%20for%20the%20classification,to%20the%20ADG%20code%20packing%20group%20I-III. |access-date=March 23, 2025 |website=WorkSafe |quote=In the European/Australian system, flammable liquids are designated "Class B" having flash points no more than 93°C.}}</ref>}}. Examples may include [[gasoline|petrol/gasoline]], [[petroleum|oil]], [[paint]], some [[wax]]es & plastics, though cooking fats and oils are explicitly excluded (discussed and categorised separately below).

A solid stream of water should never be used to extinguish this type of fire because it can cause the fuel to scatter, spreading the flames.<ref name=":7" /> The most effective way to extinguish a liquid fire is by inhibiting the chemical chain reaction of the fire, which can be done by dry chemical or [[Halomethane|Halon]] extinguishing agents.<ref name=":3">{{Cite web |title=NFPA 10 Standard Development |url=https://www.nfpa.org/codes-and-standards/nfpa-10-standard-development/10 |access-date=March 31, 2025 |website=www.nfpa.org |language=en}}</ref> Smothering with [[CO2|CO<sub>2</sub>]] or foam is also effective. Halon has fallen out of favor in recent times (except for aircraft fire extinguishing systems) because it is an [[Ozone depletion|ozone-depleting]] material (the [[Montreal Protocol]] declares that Halon should no longer be used). Chemicals such as [[FM-200]] are now the recommended halogenated suppressant.<ref>{{Cite web |date=May 8, 2008 |title=Wollongong Extinguisher Service-Australia. For Fire Extinguishers. |url=https://web.archive.org/web/20080508224118/http://www.fireservice.com.au/extinguisher.html |access-date=March 23, 2025 |website=web.archive.org}}</ref>

{{notelist-num}}

=== Flammable gases: Class B (US) / Class C (EU/AU) ===
[[File:Fire Gas.png|left|60px]]
Fires involving flammable [[gas]]es fall under '''Class C''' in the European/Australian system, and '''Class B''' (along with flammable liquids) in the US system.<ref name=":5">{{Cite web |title=AS/NZS 1841.1:2007 4 |url=http://www.top-safefire.com/uploadfile/2013092821213983579.pdf |access-date=March 31, 2025 |website= |language=en}}</ref><ref name=":3" /><ref name=":4">{{Cite web |last=Standards |first=European |title=BS EN 2:1992 Classification of fires |url=https://www.en-standard.eu/bs-en-2-1992-classification-of-fires/ |access-date=March 31, 2025 |website=www.en-standard.eu |language=en}}</ref> This can include [[natural gas]], [[hydrogen]], [[propane]], and [[butane]].

Due to the nature of the fuel, these fires can be difficult to extinguish. The most effective techniques for the control of a flammable gas fire are to stop the flow of fuel (by turning off any gas taps or valves) or to displace the supply of oxygen.<ref name=":0" /> Control of fires involving flammable gases where the gas source cannot be controlled must be carefully managed. If the flames are extinguished, but the gas continues to leak, an explosive atmosphere may be created, and the gas may find a source for reignition outside of the originally affected area. Strategies employed to manage these fires may include trying to direct or contain the fire to prevent the ignition of other fuels whilst work is done to control the fuel supply.<ref name=":2" />

=== Combustible metals: Class D (US/EU/AU) ===
{{anchor|Metal}} [[File:Fire Metal.png|left|60px]]
Fires involving combustible [[metal]]s fall under '''Class D'''. This especially concerns [[alkali metal]]s like [[lithium]], [[potassium]] and [[sodium]], [[alkaline earth metal]]s such as [[magnesium]], and [[group 4 element]]s such as [[titanium]] and [[zirconium]].<ref name=IFSTA-10/>

Metal fires represent a unique hazard because people are often unaware of the characteristics of these fires and are not properly prepared to fight them.<ref name="IFSTA-10" /> It is also not always clear what type of metal is burning. Certain metals [[Pyrophoricity|catch fire in contact with air or water]] (for example, [[sodium]]), which exacerbates this risk.<ref name=":4" /> Monolithic masses of combustible metals do not usually represent great fire risks because heat is conducted away from hot spots so efficiently that the heat of combustion cannot be maintained. In consequence, significant heat energy is required to ignite a contiguous mass of combustible metal. Generally, metal fires are a hazard when the metal is in the form of [[swarf]] which combusts more rapidly than larger blocks due to the increased [[surface-area-to-volume ratio]].<ref name=":3" /><ref name=":4" /> Metal fires can be ignited by the same ignition sources that would start other common fires.<ref name=":3" />

Special care must be taken when extinguishing metal fires. Water and other common firefighting agents can exacerbate them.<ref name=":3" /> The [[National Fire Protection Association]] recommends that metal fires be fought with dry powder extinguishing agents that work by smothering and heat absorption.<ref name=":3" /> Different metals require different extinguishing agents and for a particular metal, agents cannot necessarily be substituted for one another. The most common agents are [[sodium chloride]] granules and [[graphite]] powder.<ref name=":4" /> In recent years,{{When|date=June 2025}} powdered [[copper]] has also come into use.<ref name=":4" /> These ''dry powder'' extinguishers should not be confused with those that contain ''dry chemical'' agents. The two are not the same, and only dry powder should be used to extinguish a metal fire. Using a dry chemical extinguisher in error, in place of dry powder, can be ineffective or actually increase the intensity of a metal fire.<ref name=":3" /> Lacking a specialist extinguisher, [[sand]] may in some cases provide a sufficient alternative, though notably sand may contain moisture which could result in a rapid, hazardous release of steam.<ref name=":11">{{Cite web |date=June 1, 2025 |title=Extinguishers For Metals |url=https://www.fireextinguisherguide.co.uk/types-of-fire-extinguishers/extinguishers-for-metals-2/ |url-status=live |access-date=June 1, 2025}}</ref>

=== Electrical fires: Class C (US) / Class E (AU) / Unclassified (EU) ===
{{Anchor|Electrical}}
{{Redirect-distinguish|Electrical fire|Electric fire (disambiguation){{!}}Electric fire}}
[[File:Fire Electrical.png|left|60px]]
[[File:Damage from energized fallen power line caused by Hurricane Maria in Puerto Rico.jpg|thumb|upright|Road damage from an electrical fire caused by energized fallen power line caused by [[Hurricane Maria]] in [[Puerto Rico]]]]
Fires involving the danger of [[electrical]] hazards fall under '''Class E''' under the Australian system, and '''Class C''' under the US system.<ref name=":0"/> The European system previously assigned this '''Class E''', but no longer has a specific classification for electrical fires, instead focussing on the ignited fuel type.

Electrical fires can result from the likes of faulty electrical equipment or wiring<ref name=":3" /> (for instance loose or corroded connections; deteriorated insulation; [[electric arc|electrical arcing]]), overheating electrical components (possibly due to improper system or product design), or unintentional contact of electrical or electronic components with flammable materials. These fires can be a severe hazard to firefighters using water or other conductive agents, which upon contact with electrical sources can establish a conductive path through the firefighter to [[ground (electrical)|Earth]]. Such [[Electrical shocks|electric shocks]] have caused many firefighter deaths.<ref name=":3" />

Electrical fires may be fought in the same way as an ordinary combustible fire, but water, foam, and other conductive agents should not be used due to the dangers just described. Instead an extinguishing agent specifically rated for electrical fires should be used. [[Carbon dioxide]] (CO<sub>2</sub>), NOVEC 1230, [[FM-200]], dry chemical powder extinguishers, and even baking soda are especially suited to extinguishing this sort of fire.<ref name=":7" /> [[Purple-K|PKP]] should be a last resort solution due to its corrosive tendencies.

Once electricity is shut off to the equipment involved, it will generally become an ordinary combustible fire.<ref name=":7" />

=== Grease fires (cooking): Class F (EU/AU) / Class K (US) ===
[[File:Fire Cooking Oil.png|left|60px]]
[[File:Chip-pan-fire.jpg|upright|thumb|Laboratory simulation of a [[Chip_pan#Fire_hazard|chip pan fire]]: a beaker containing wax is heated until it catches fire. A small amount of water is then poured into the beaker. The water vaporizes instantly (''[[Boilover#Related phenomena|slopover]]''), expanding to 1700 times its volume,<ref name=":7">{{Cite web |title=Classes of Fires & Fire Extinguishers - Safety {{!}} UCLA Health |url=https://www.uclahealth.org/safety/ambulatory-safety/ambulatory-fire-and-life-safety-program/classes-fires-fire-extinguishers?utm_source=chatgpt.com |access-date=2025-04-12 |website=www.uclahealth.org |language=en}}</ref> ejecting a plume of burning liquid wax into the air.]]

Fires involving [[cooking oil]]s and [[fat]]s (greases) fall under '''Class F''' under the European and Australian systems, and '''Class K''' under the US system.<ref name=":1" /><ref name=":0" /><ref name=":5" /> Though such fires are technically a subclass of the flammable liquid/gas class(es), the special characteristics of these types of fires, namely the higher flash point, are considered important enough to recognize them separately.

Some special extinguishers designed for this use smother the fire by turning the oil into a foam. As with Class B fires, a solid stream of water should never be used to extinguish this type because it can cause the fuel to scatter, spreading the flames.<ref name=":3" /> Commercial kitchens may have a fire suppression system built into exhaust hoods to release an extinguishing agent onto stove tops, releasing automatically with a fusible link or manually using a pull station.<ref name=":5" />

If a [[fire blanket]] is used to extinguish burning liquids the liquid can soak into the blanket. A hot liquid might then lead to the self-ignition of the blanket.<ref name=":0" /> A blanket must therefore only be used if it does not act as a [[Capillary action|wick]] or if it is heavy enough to cool the liquid down below [[autoignition temperature]]. Preferably a lid or a similar solid item should be used to seal the burning container off from the surrounding atmosphere.<ref name=":6" />
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==Comparison==

Comparison of letter codes in different regional standards.

{| class="wikitable"
|-
! rowspan="2" | Type of fire
! colspan="3" | Class
|-
! Australia
! Europe
! United States
|-
| Flammable solids
| A
| A
| A
|-
| Flammable liquids, excluding cooking fats and oils
| B
| B
| B
|-
| Flammable gases
| C
| C
| B
|-
| Combustible metals
| D
| D
| D
|-
| Electrical fires
| E{{efn|name=class-e|Technically there is no such thing as a "Class E" fire, as electricity itself obviously does not burn. However, it is considered a dangerous and very deadly complication to a fire, therefore using the incorrect extinguishing method can result in serious injury or death. Class E, however generally refers to fires involving the danger of electricity, therefore a bracketed "(E)" is denoted on various types of extinguishers suitable for such scenarios.<ref>New South Wales Rural Fire Service VF - (2005) Village Firefighter Manual, pg 16.</ref>}}
| Unclassified (formerly E{{efn|name=class-e}})
| C
|-
| Grease fires (cooking fats and oils)
| F
| F
| K
|}

{{notelist}}

== See also ==
* [[Fire control]]
* [[Fire extinguisher]]

== References ==
{{Reflist}}

== External links ==
* [https://web.archive.org/web/20080401035246/http://www.osha.gov/doc/outreachtraining/htmlfiles/extmark.html Classification of Portable Fire Extinguishers], [[Occupational Safety and Health Administration]]
* [http://www.osha.gov/SLTC/etools/evacuation/portable_about.html Evacuation Plans and Procedures eTool], [[Occupational Safety and Health Administration]]
* [http://www.firesafe.org.uk/html/fsequip/exting.htm Information on Fire Extinguishers], The Fire Safety Advice Centre
* [https://futurafire.com/fire-class/ Australian Fire Classes], Futura Fire – Australia
* [https://web.archive.org/web/20080508224118/http://www.fireservice.com.au/extinguisher.html For Fire Extinguishers], Wollongong Extinguisher Service-Australia

{{Fire fighting}}
{{Fire protection}}

{{DEFAULTSORT:Fire Classes}}
[[Category:Classification systems]]
[[Category:Firefighting]]

Fire classification - Revision history

imported>Kovcszaln6: /* Combustible metals: Class D (US/EU/AU) */ when?