A
fire extinguisher is an
active fire protection device used to extinguish or control small fires, often in emergency situations. It is not intended for use on an out-of-control fire, such as one which has reached the
ceiling, endangers the user (i.e., no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a
fire department. Typically, a fire extinguisher consists of a hand-held cylindrical
pressure vessel containing an
agent which can be discharged to extinguish a
fire.
In the United States, fire extinguishers, in all buildings other than houses, are generally required to be serviced and inspected by a Fire Protection service company at least annually. Some jurisdictions require more frequent service for fire extinguishers. The servicer places a tag on the extinguisher to indicate the type of service performed (annual inspection, recharge, new fire extinguisher) and when.
There are two main types of fire extinguishers: stored pressure and cartridge-operated. In stored pressure units, the expellant is stored in the same chamber as the
firefighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers,
nitrogen is typically used; water and foam extinguishers typically use air. Stored pressure fire extinguishers are the most common type. Cartridge-operated extinguishers contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the extinguishing agent. This type is not as common, used primarily in areas such as industrial facilities, where they receive higher-than-average use. They have the advantage of simple and prompt recharge, allowing an operator to discharge the extinguisher, recharge it, and return to the fire in a reasonable amount of time. Unlike stored pressure types, these extinguishers use compressed
carbon dioxide instead of nitrogen, although nitrogen cartridges are used on low temperature (-60 rated) models. Cartridge operated extinguishers are available in dry chemical and dry powder types in the US and in water, wetting agent, foam, dry chemical (classes ABC and BC), and dry powder (class D) types in the rest of the world.
A fire extinguisher located in a middle school.
Fire extinguishers are further divided into handheld and cart-mounted, also called wheeled extinguishers. Handheld extinguishers weigh from 0.5 to 14 kilograms (1 to 30 pounds), and are hence, easily portable by hand. Cart-mounted units typically weigh 23+ kilograms (50+ pounds). These wheeled models are most commonly found at
construction sites,
airport runways,
heliports, as well as
docks and
marinas.
The first fire extinguisher of which there is any record was patented in England in 1723 by
Ambrose Godfrey, a celebrated chemist. It consisted of a cask of fire-extinguishing liquid containing a pewter chamber of gunpowder. This was connected with a system of fuses which were ignited, exploding the gunpowder and scattering the solution. This device was probably used to a limited extent, as Bradley's Weekly Messenger for November 7, 1729, refers to its efficiency in stopping a fire in London.
The modern fire extinguisher was invented by British Captain
George William Manby in 1818; it consisted of a copper vessel of 3
gallons (13.6
liters) of pearl ash (
potassium carbonate) solution contained within
compressed air.
A classic copper building type soda-acid extinguisher
The soda-acid extinguisher was first patented in 1866 by Francois Carlier of France, which mixed a solution of water and sodium bicarbonate with
tartaric acid, producing the propellant CO
2 gas. A soda-acid extinguisher was patented in the U.S. in 1881 by
Almon M. Granger. His extinguisher used the reaction between
sodium bicarbonate solution and
sulfuric acid to expel pressurized water onto a fire.
[1] A vial was suspended in the cylinder containing concentrated
sulfuric acid. Depending on the type of extinguisher, the vial of acid could be broken in one of two ways. One used a plunger to break the acid vial, while the second released a lead stopple that held the vial closed. Once the acid was mixed with the bicarbonate solution,
carbon dioxide gas was expelled and thereby pressurized the water. The pressurized water was forced from the canister through a nozzle or short length of hose.
The cartridge-operated extinguisher was invented by Read & Campbell of England in 1881, which used water or water-based solutions. They later invented a carbon tetrachloride model called the "Petrolex" which was marketed toward automotive use.
[2]
A glass "grenade" style extinguisher, to be thrown into a fire.
The chemical foam extinguisher was invented in 1904 by
Aleksandr Loran in Russia, based on his previous invention of
fire fighting foam. Loran first used it to extinguish a pan of burning naphtha.
[3] It worked and looked similar to the soda-acid type, but the inner parts were slightly different. The main tank contained a solution of sodium bicarbonate in water, whilst the inner container (somewhat larger than the equivalent in a Soda-Acid unit) contained a solution of Aluminium Sulphate. When the solutions were mixed, usually by inverting the unit, the two liquids reacted to create a frothy foam, and carbon dioxide gas. The gas expelled the foam in the form of a jet. Although liquorice-root extracts and similar compounds were used as additives (stabilizing the foam by reinforcing the bubble-walls), there was no "foam compound" in these units. The foam was a combination of the products of the chemical reactions: Sodium and Aluminium salt-gels inflated by the carbon-dioxide. Because of this, the foam was discharged directly from the unit, with no need for an aspirating branchpipe (as in newer foam-compound types).
A Pyrene, brass, carbon-tetrachloride extinguisher
In 1910, The Pyrene Manufacturing Company of Delaware filed a patent for a using
carbon tetrachloride (CTC) to extinguish fires.
[4] The liquid vaporized and extinguished the flames by inhibiting the chemical chain reaction of the combustion process (it was an early 20th century presupposition that the fire suppression ability of carbon tetrachloride relied on oxygen removal.) In 1911, they patented a small, portable extinguisher that used the chemical.
[5] This consisted of a
brass or
chrome container with an integrated handpump, which was used to expel a jet of liquid towards the fire. It was usually of 1 imperial
quart (1.1 L) or 1 imperial
pint (0.6 L) capacity but was also available in up to 2 imperial gallon (9 L) size. As the container was unpressurized, it could be refilled after use through a filling plug with a fresh supply of CTC.
[6]
Another type of carbon-tetrachloride extinguisher was the
Fire grenade. This consisted of a glass sphere filled with CTC, that was intended to be hurled at the base of a fire (early ones used salt-water, but CTC was more effective). Carbon tetrachloride was suitable for liquid and electrical fires and the extinguisers were fitted to motor vehicles. Carbon-tetrachloride extinguishers were withdrawn in the 1950s because of the chemical's toxicity–exposure to high concentrations damages the nervous system and internal organs. Additionally, when used on a fire, the heat can convert CTC to
Phosgene gas ,
[7] formerly used as a chemical weapon.
In the 1940s, Germany invented the liquid
chlorobromomethane (CBM) for use in aircraft. It was more effective and slightly less toxic than carbon tetrachloride and was used until 1969.
Methyl bromide was discovered as an extinguishing agent in the 1920s and was used extensively in Europe. It is a low-pressure gas that works by inhibiting the chain reaction of the fire and is the most toxic of the vaporizing liquids, used until the 1960s. The vapor and combustion by-products of all vaporizing liquids were highly toxic, and could cause death in confined spaces.
A chemical foam extinguisher with contents.
The carbon dioxide (CO
2) extinguisher was invented (at least in the US) by the Walter Kidde Company in 1924 in response to Bell Telephone's request for an electrically non-conductive chemical for extinguishing the previously difficult to extinguish fires in telephone switchboards. It consisted of a tall metal cylinder containing 7.5 lbs. of CO
2 with a wheel valve and a woven brass, cotton covered hose, with a composite funnel-like horn as a nozzle. CO
2 is still popular today as it is an ozone-friendly clean agent and is used heavily in film and television production to extinguish burning
stuntmen.
[8] Carbon dioxide extinguishes fire mainly by displacing oxygen. It was once thought that it worked by cooling, although this effect on most fires is negligible. This characteristic is well known and has led to the widespread misuse of carbon dioxide extinguishers to rapidly cool beverages, especially
beer.
An early dry chemical extinguisher, the first ones had copper cylinders, this one is steel.
In 1928, DuGas (later bought by
ANSUL) came out with a cartridge-operated dry chemical extinguisher, which used sodium bicarbonate specially treated with chemicals to render it free-flowing and moisture-resistant. It consisted of a copper cylinder with an internal CO
2cartridge. The operator turned a wheel valve on top to puncture the cartridge and squeezed a lever on the valve at the end of the hose to discharge the chemical. This was the first agent available for large scale three-dimensional liquid and pressurized gas fires, and was but remained largely a specialty type until the 1950s, when small dry chemical units were marketed for home use. ABC dry chemical came over from Europe in the 1950s, with Super-K being invented in the early 60s and Purple-K being developed by the US Navy in the late 1960s.
In the 1970s, Halon 1211 came over to the US from Europe, where it had been used since the late 40s or early 50s. Halon 1301 had been developed by DuPont and the US Army in 1954. Both 1211 and 1301 work by inhibiting the chain reaction of the fire, and in the case of Halon 1211, cooling class A fuels as well. Halon is still in use today, but is falling out of favor for many uses due to its environmental impact. Europe, and Australia have severely restricted its use, since the Montreal Protocol of 1987. It is however still in use in the United States, the Middle East, and Asia.
Dry chemical
-
A small, disposable sodium bicarbonate dry chemical unit intended for home kitchen use.
-
A typical dry chemical extinguisher containing 5 lbs. of ammonium phosphate dry chemical.
-
A 20lb.U.S.Navy cartridge-operated purple-K dry chemical (potassium bicarbonate) extinguisher.
-
Two Super-K (potassium chloride) extinguishers.
This is a powder based agent that extinguishes by separating the four parts of the
fire tetrahedron. It prevents the chemical reaction involving heat, fuel, and oxygen and halts the production of fire sustaining "free-radicals", thus extinguishing the fire.
- Monoammonium phosphate, also known as "tri-class", "multipurpose" or "ABC" dry chemical, used on class A, B, and C fires. It receives its class A rating from the agent's ability to melt and flow at 177 °C (350 °F) to smother the fire. More corrosive than other dry chemical agents. Pale yellow in color.
- Sodium bicarbonate, "regular" or "ordinary" used on class B and C fires, was the first of the dry chemical agents developed. In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That is the gas drives oxygen away from the fire, thus stopping the chemical reaction. This agent is not generally effective on class A fires because the agent is expended and the cloud of case dissipates quickly, and if the fuel is still sufficiently hot, the fire starts up again. While liquid and gas fires don't usually store much heat in their fuel source, solid fires do. Sodium bicarbonate was very common in commercial kitchens before the advent of wet chemical agents, but now is falling out of favor, as it is much less effective than wet chemical agents for class K fires, less effective than Purple-K for class B fires, and is ineffective on class A fires. White or blue in color.
- Potassium bicarbonate (aka Purple-K), used on class B and C fires. About two times as effective on class B fires as sodium bicarbonate, it is the preferred dry chemical agent of the oil and gas industry. The only dry chemical agent certified for use in ARFF by the NFPA. Violet in color.
- Potassium bicarbonate & Urea Complex (aka Monnex/Powerex), used on Class B and C fires. More effective than all other powders due to its ability to decrepitate (where the powder breaks up into smaller particles) in the flame zone creating a larger surface area for free radical inhibition. Grey in color.
- Potassium Chloride, or Super-K dry chemical was developed in an effort to create a high efficiency, protein-foam compatible dry chemical. Developed in the 60s, prior to Purple-K, it was never as popular as other agents since, being a salt, it was quite corrosive. For B and C fires, white in color.
- Foam-Compatible, which is a sodium bicarbonate (BC) based dry chemical, was developed for use with protein foams for fighting class B fires. Most dry chemicals contain metal stearates to waterproof them, but these will tend to destroy the foam blanket created by protein (animal) based foams. Foam compatible type uses silicone as a waterproofing agent, which does not harm foam. Effectiveness is identical to regular dry chemical, and it is light green in color (some ANSUL brand formulations are blue). This agent is generally no longer used since most modern dry chemicals are considered compatible with synthetic foams such as AFFF.
- MET-L-KYL / PYROKYL is a specialty variation of sodium bicarbonate for fighting pyrophoric liquid fires (ignite on contact with air). In addition to sodium bicarbonate, it also contains silica gel particles. The sodium bicarbonate interrupts the chain reaction of the fuel and the silica soaks up any unburned fuel, preventing contact with air. It is effective on other class B fuels as well. Blue/Red in color.
A 2½ gallon AFFF foam fire extinguisher
Applied to fuel fires as either an aspirated (mixed & expanded with air in a branch pipe) or non aspirated form to form a frothy blanket or seal over the fuel, preventing oxygen reaching it. Unlike powder, foam can be used to progressively extinguish fires without flashback.
- AFFF (aqueous film forming foam), used on A and B fires and for vapor suppression. The most common type in portable foam extinguishers. It contains fluoro tensides [12] which can be accumulated in human body. The long-term effects of this on the human body and environment are unclear at this time.
- AR-AFFF (Alcohol-resistant aqueous film forming foams), used on fuel fires containing alcohol. Forms a membrane between the fuel and the foam preventing the alcohol from breaking down the foam blanket.
- FFFP (film forming fluoroprotein) contains naturally occurring proteins from animal by-products and synthetic film-forming agents to create a foam blanket that is more heat resistant than the strictly synthetic AFFF foams. FFFP works well on alcohol-based liquids and is used widely in motorsports.
- CAFS (compressed air foam system) Any APW style extinguisher that is charged with a foam solution and pressurized with compressed air. Generally used to extend a water supply in wildland operations. Used on class A fires and with very dry foam on class B for vapor suppression.
- Arctic Fire is a liquid fire extinguishing agent that emulsifies and cools heated materials more quickly than water or ordinary foam. It is used extensively in the steel industry. Effective on classes A, B, and D.
- FireAde, a foaming agent that emulsifies burning liquids and renders them non-flammable. It is able to cool heated material and surfaces similar to CAFS. Used on A and B (said to be effective on some class D hazards, although not recommended due to the fact that fireade still contains amounts of water which will react with some metal fires).
An American water extinguisher
Cools burning material.
- APW (Air pressurized water) cools burning material by absorbing heat from burning material. Effective on Class A fires, it has the advantage of being inexpensive, harmless, and relatively easy to clean up. In the United States, APW units contain 2.5 gallons (9 liters) of water in a tall, stainless steel cylinder. In Europe, they are typically mild steel lined with polyethylene, painted red, containing 6–9 liters (1.75–2.5 gallons) of water.
- Water Mist uses a fine misting nozzle to break up a stream of deionized water to the point of not conducting electricity back to the operator. Class A and C rated. It is used widely in hospitals for the reason that, unlike other clean-agent suppressants, it is harmless and non-contaminant. These extinguishers come in 1.75 and 2.5 gallon units, painted white in the United States and red in Europe.
[edit] Wet chemical and water additives
- Wet Chemical (potassium acetate, carbonate, or citrate) extinguishes the fire by forming a soapy foam blanket over the burning oil and by cooling the oil below its ignition temperature. Generally class A and K (F in Europe) only, although newer models are outfitted with misting nozzles as those used on water mist units to give these extinguishers class B and C firefighting capability.
- Wetting Agents Detergent based additives used to break the surface tension of water and improve penetration of Class A fires.
- Antifreeze Chemicals added to water to lower its freezing point to about −40 °F. Has no appreciable effect on extinguishing performance.
[edit] Clean agents and carbon dioxide
A 5 lb. CO
2 fire extinguisher
Agent displaces oxygen (CO
2 or inert gases), removes heat from the combustion zone (Halotron, FE-36) or inhibits chemical chain reaction (Halons). They are labelled clean agents because they do not leave any residue after discharge which is ideal for sensitive electronics and documents.
- Halon (including Halon 1211 and Halon 1301), a gaseous agent that inhibits the chemical reaction of the fire. Classes B:C for lower weight fire extinguishers (2.3 kg; under 9 lbs) and A:B:C for heavier weights (4.1–7.7 kg; 9–17 lbs). Banned from new production, except for military use, as of January 1, 1994 as its properties contribute to ozone depletion and long atmospheric lifetime, usually 400 years. Halon was completely banned in Europe resulting in stockpiles being sent to the United States for reuse. Although production has been banned, the reuse is still permitted. Halon 1301 and 1211 are being replaced with new halocarbon agents which have no ozone depletion properties and low atmospheric lifetimes, but are less effective. Currently Halotron I, Halotron II, FE-36 Cleanguard and FM-200 are meant to be replacements with significantly reduced ozone depletion potential.
- CO2, a clean gaseous agent which displaces oxygen. Highest rating for 7.7 kg (20 pound) portable CO2 extinguishers is 10B:C. Not intended for Class A fires, as the high-pressure cloud of gas can scatter burning materials. CO2 is not suitable for use on fires containing their own oxygen source, metals or cooking media. Although it can be rather successful on a person on fire, its use should be avoided where possible as it can cause frostbite and is dangerous to use as it may displace the oxygen needed for breathing, causing suffocation.
- Mixtures of inert gases, including Inergen and Argonite.
- compressed CO2 sprinkler is another design used to fight the electric fires with cubic cylinder of 7 cubic meter starting from 1 meter above the sprinkler level.
- Novec 1230 fluid (aka "dry water" or Saffire fluid), a fluoronated ketone that works by removing massive amounts of heat. Available in fixed systems in the US and in portables in Australia. Unlike other clean agents, this one has the advantage of being a liquid at atmospheric pressure, and can be discharged as a stream or a rapidly vaporizing mist, depending on application.
- Potassium Aerosol Particle Generator, contains a form of solid potassium and other chemicals referred to as Aerosol Forming Compounds (AFC). The AFC is activated by an electrical current or other thermodynamic exchange which causes the AFC to ignite. The Majority of installed currently are fixed units due to the possibility of harm to the user from the heat generated by the AFC generator.
[edit] Class D
A class D fire extinguisher for various metals
There are several Class D fire extinguisher agents available, some will handle multiple types of metals, others will not.
- Copper based (Copper Powder Navy125S) developed by the U.S. Navy in the 70s for hard-to-control lithium and lithium-alloy fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface-lithium only.
- Graphite based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR) contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well. Unlike sodium chloride powder extinguishers, the graphite powder fire extinguishers can be used on very hot burning metal fires such as lithium, but unlike copper powder extinguishers will not stick to and extinguish flowing or vertical lithium fires. Like copper extinguishers, the graphite powder acts as a heat sink as well as smothering the metal fire.
- Sodium carbonate based (Na-X) used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. Limited use on other metals. Smothers and forms a crust.
- Some water based suppressants may be used on certain class D fires, such as burning titanium and magnesium. Examples include the Fire Blockade and FireAde brands of suppressant.[13][14] Some metals, such as elemental Lithium, will react explosively with water, therefore water-based chemicals should never be used on such fires due to the possibility of a violent reaction.
Most Class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel.
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