fire extinguisher

History

The first fire extinguisher of which there is any record was patented in England in 1723 by Ambrose Godfrey, a celebrated chemist at that time. 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.

A portable pressurised fire extinguisher, the 'Extincteur', was invented by British Captain George William Manby and demonstrated in 1816 to the 'Commissioners for the affairs of Barracks'; it consisted of a copper vessel of 3 gallons (13.6 liters) of pearl ash (potassium carbonate) solution contained within compressed air. When operated it expelled liquid onto the fire.

One of the first fire extinguisher patents was issued to Alanson Crane of Virginia on Feb. 10, 1863.

Thomas J. Martin, an American inventor, was awarded a patent for an improvement in the Fire Extinguishers on March 26, 1872. His invention is listed in the U. S. Patent Office in Washington, DC under patent number 125,603.

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 carbon dioxide (CO2) gas. A soda-acid extinguisher was patented in the U.S. in 1880 by Almon M. Granger. His extinguisher used the reaction between sodium bicarbonate solution and sulfuric acid to expel pressurized water onto a fire. A vial of concentrated sulfuric acid was suspended in the cylinder. 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.

Classification

Internationally there are several accepted classification methods for hand-held fire extinguishers. Each classification is useful in fighting fires with a particular group of fuel.

Australia and New Zealand

Specifications of fire extinguishers are set out in the standard AS/NZS 1841, the most recent version having been released in 2007. All fire extinguishers must be painted signal red. Except for water based extinguishers, each extinguisher has a coloured band near the top, covering at least 10% of the extinguisher's body length, specifying its contents.

Due to the ozone-depleting nature of halon, in Australia yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted.

United Kingdom

According to British standard BS EN 3, fire extinguishers in the United Kingdom, same as throughout Europe, are red RAL 3000, with a band or circle of a second color covering between 5–10% of the surface area of the extinguisher, above the operating instructions, indicating its contents. Before 1997, the entire body of the fire extinguisher was color coded according to the type of extinguishing agent.

The UK recognises five fire classes:

Class A fires involve organic solids such as paper and wood.

Class B fires involve flammable or combustible liquids, excluding cooking fats and oils.

Class C fires involve flammable gases.

Class D fires involve combustible metals.

Class K fires involve cooking fats and oils.

Class E has been discontinued, previously covering fires involving electrical hazards. This is no longer used on the basis that, when the power supply is turned off, an electrical fire can fall into any of the remaining five categories. EN3 does however allow extinguishers to bear a special electrical pictogram signifying that it can be used on live electrical fires (given the symbol E in the table), if it passes special testing (a 35 kV dielectric test per EN 3-7:2004). A powder or CO2 extinguisher will feature this as standard. A water-based extinguisher may feature it if it passes the 35 kV test, however all water-based extinguishers are only recommended for inadvertent use on electrical fires.

In the UK, the use of Halon gas is now prohibited except under certain situations such as on aircraft and in the military and police.

Fire extinguishing performance per fire class is displayed using numbers and letters such as 13A, 55B.

United States

There is no official standard in the United States for the color of fire extinguishers, though they are usually red, except for class D extinguishers which are usually yellow, water and Class K wet chemical extinguishers which are usually silver, and water mist extinguishers which are usually white. Extinguishers are marked with pictograms depicting the types of fires that the extinguisher is approved to fight. In the past extinguishers were marked with colored geometric symbols, and some extinguishers still use both symbols. The types of fires and additional standards are described in NFPA 10: Standard for Portable Fire Extinguishers, 2013 edition.

Fire extinguishing capacity is rated in accordance with ANSI/UL 711: Rating and Fire Testing of Fire Extinguishers. The ratings are described using numbers preceding the class letter, such as 1-A:10-B:C. The number preceding the A multiplied by 1.25 gives the equivalent extinguishing capability in gallons of water. The number preceding the B indicates the size of fire in square feet that an ordinary user should be able to extinguish. There is no additional rating for class C, as it only indicates that the extinguishing agent will not conduct electricity, and an extinguisher will never have a rating of just C.

Installation

Fire extinguishers are usually fitted in buildings at an easily accessible location, such as against a wall in a high-traffic area. They are also often fitted to motor vehicles, watercraft, and aircraft – this is required by law in many jurisdictions, for identified classes of vehicles. Under NFPA 10 all commercial vehicles must carry at least one fire extinguisher, with size/UL rating depending on type of vehicle and cargo (i.e., fuel tankers usually must have a 20 lb (9.1 kg), while most others can carry a 5 lb (2.3 kg)). The revised NFPA 10 created criteria on the placement of "fast flow extinguishers" in locations such as those storing and transporting pressurized flammable liquids and pressurized flammable gas or areas with possibility of three-dimensional class B hazards are required to have "fast flow extinguishers" as required by NFPA 5.5.1.1. Varying classes of competition vehicles require fire extinguishing systems, the simplest requirements being a 1A:10BC hand-held portable extinguisher mounted to the interior of the vehicle.

The height limit for installation, as determined by the NFPA, is 60 in (1.5 m) for fire extinguishers weighing less than 40 lb (18 kg). However, compliance with the Americans with Disabilities Act (ADA) also needs to be followed within the United States. The ADA height limit of the fire extinguisher, as measured at the handle, is 48 in (1.2 m). Fire extinguisher installations are also limited to protruding no more than 4 inches into the adjacent path of travel. The ADA rule states that any object adjacent to a path of travel may not project more than 4 in (10 cm) if the object's bottom leading edge is higher than 27 in (0.69 m). The 4-inch protrusion rule was designed to protect people with low-vision and those who are blind. The height limit rule of 48 inches is primarily related to access by people with wheelchairs but it is also related to other disabilities as well. Prior to 2012, the height limit was 54 in (1.4 m) for side-reach by wheelchair-accessible installations. Installations made prior to 2012 at the 54-inch height are not required to be changed.

In New Zealand, the mandatory installation of fire extinguishers in vehicles is limited to self-propelled plant in agriculture and arboriculture, passenger service vehicles with more than 12 seats and vehicles that carry flammable goods. NZ Transport Agency recommends that all company vehicles carry a fire extinguisher, including passenger cars.

Fire extinguishers mounted inside aircraft engines are called extinguishing bottles or fire bottles.

Types of extinguishing agents

Different types of extinguishing agents have different modes of action, and certain ones are only appropriate for specific fire classes.

Dry chemical

This is a powder-based agent that extinguishes by separating the three parts of the fire triangle. It prevents the chemical reactions involving heat, fuel, and oxygen, thus extinguishing the fire. During combustion, the fuel breaks down into free radicals, which are highly reactive fragments of molecules that react with oxygen. The substances in dry chemical extinguishers can stop this process.

Monoammonium phosphate, also known as ABC dry chemical, tri-class, or multipurpose, is used on class A, B and C fires. It receives its class A rating from the agent's ability to melt and flow at 190 °C (374 °F) to smother the fire. It is more corrosive than other dry chemical agents and is 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 gas dissipates quickly, and if the fuel is still sufficiently hot, the fire starts up again. While liquid and gas fires do not 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 (principal constituent of 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. Colored violet to distinguish it.

Potassium bicarbonate & Urea Complex (AKA Monnex), 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 1960s, 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.

Foams

Applied to fuel fires as either an aspirated (mixed and expanded with air in a branch pipe) or nonaspirated form to create a frothy blanket or seal over the fuel, preventing oxygen reaching it. Unlike powder, foam can be used to progressively extinguish fires without flashback.

Aqueous film-forming foam (AFFF), used on A and B fires and for vapor suppression. The most common type is portable foam extinguishers. AFFF was developed in the 1960s under Project Light Water in a joint venture between 3M and the U.S. Navy. AFFF forms a film that floats out before the foam blanket, sealing the surface and smothering the fire by excluding oxygen. AFFF is widely used for ARFF firefighting at airports, often in conjunction with purple-K dry chemical. It contains fluoro-tensides which can be accumulated in the human body. The long-term effects of this on the human body and environment are unclear at this time. AFFF can be discharged through an air-aspirating branchpipe nozzle or a spray nozzle and is now produced only in pre-mix form, where the foam concentrate is stored mixed with water. In the past, as solid charge model was produced, the AFFF concentrate was housed as a dry compound in an external, disposable cartridge in a specially designed nozzle. The extinguisher body was charged with plain water, and the discharge pressure mixed the foam concentrate with the water upon squeezing the lever. These extinguishers received double the rating of a pre-mix model (40-B instead of 20-B), but are now considered obsolete, as parts and refill cartridges have been discontinued by the manufacturer. European regulations require the phasing out of AFFF foams containing persistent organic pollutants. These include PFAS (Per and PolyFluoroAlkylated Substances), PFOA (PerFluoroOctanoic Acid), its salts or PFOA related compounds, and PFOS (PerFluoroOctane Sulphonic acid), its salts or PFOS related compounds. Related derogations allowing delay of their removal are to end on 4 July 2025. As of April 2024, listed foam extinguishers using traditional AFFF formulas are no longer being produced for the US market, with Amerex announcing their exit from manufacturing foam extinguishers in December 2021, and Badger in March 2024, respectively. Once existing stocks of charges and parts are depleted, the UL listings on these units will be void and they will require replacement with other extinguisher types. Buckeye has announced that they will be producing models FFE-6L and FFE-2.5 as of April 2024, using 3% AFFF premix (C6 Platinum Plus concentrate) extinguishers with aspirating nozzles that contain no PFOS and less than 10 ppb PFOA, with greener formulas to come in the future, though they do not seem to be available online as of April 2024.

Alcohol-resistant aqueous film-forming foams (AR-AFFF), used on liquid fuel fires containing alcohol or other water-miscible flammable or combustible liquids (polar solvents). Forms a membrane between the fuel and the foam preventing the alcohol from breaking down the foam blanket. As of April 2024, listed foam extinguishers using traditional AR-AFFF formulas are no longer being produced for the US market, with Amerex announcing their exit from manufacturing foam extinguishers in December 2021, and Badger in March 2024, respectively. Once existing stocks of charges and parts are depleted, the UL listings on these units will be void and they will require replacement with other extinguisher types.

Water types

Water cools burning carbonaceous material and is very effective against fires in furniture, fabrics, etc. (including deep-seated fires). Water-based extinguishers cannot be used safely on energized electrical fires or flammable liquid fires.

Pump-Type water extinguisher typically consist of a 2-1/2 or 5-gallon non-pressurized metal or plastic container with a pump mounted to it, as well as a discharge hose and nozzle. Pump type water extinguishers are often used where freezing conditions may occur, as they can be economically freeze-protected with calcium chloride (except stainless steel models), such as barns, outbuildings and unheated warehouses. They are also useful where many, frequent spot fires may occur, such as during fire watch for hot work operations. They are dependent on the user's strength to produce a decent discharge stream for firefighting. Water and antifreeze are the most common, but loaded stream and foam designs were made in the past. Backpack models exist for wildland firefighting and may be solid material such as metal or fiberglass, or collapsible vinyl or rubber bags for ease of storage.

Stored pressure water cools burning material by absorbing heat via conversion of liquid water to steam. Effective on class A fires, it has the advantage of being inexpensive, harmless, and relatively easy to clean up. In the United States, stored pressure units contain 2-1/2 gallons of water in a stainless steel cylinder. In Europe, they are typically mild steel, lined with polyethylene, painted red and contain 6–9 L (1.6–2.4 US gal) of water.

Water mist uses a fine misting nozzle to break up a stream of de-ionized (minerals removed by reverse osmosis or resin column ion exchange) water to the point of not conducting electricity back to the operator. Class A and C rated. It is used widely in hospitals and MRI facilities because it is both completely non-toxic and does not cause cardiac sensitization like some gaseous clean agents. These extinguishers come in 1-3/4 and 2-1/2 gallon sizes, painted white in the United States. Models used in MRI facilities are non-magnetic and are safe for use inside the room that the MRI machine is operating. Models available in Europe come in smaller sizes as well, and some even carry a Class F rating for commercial kitchens, essentially using steam to smother the fire and the water content to cool the oil.

Additives can be used to alter the properties of water extinguishers, though additives not specified by the manufacturer will void the extinguisher's listing. These include:

Wet chemical types

Wet chemical (potassium acetate, potassium carbonate, or potassium citrate) extinguishes the fire by forming an air-excluding soapy foam blanket over the burning oil through the chemical process of saponification (a base reacting with a fat to form a soap) and by the water content cooling the oil below its ignition temperature. Generally, class A and K (F in Europe) only, although older models also achieved class B and C fire-fighting capability in the past, current models are rated A:K (Amerex, Ansul, Buckeye and Strike First) or K only (Badger/Kidde).

Clean agents

Clean agents extinguish fire by displacing oxygen (CO2 or inert gases), removing heat from the combustion zone (Halotron I, FE-36, Novec 1230) or inhibiting the chemical chain reaction (Halons, Halotron BrX). They are referred to as clean agents because they do not leave any residue after discharge, which is ideal for protecting sensitive electronics, aircraft, armored vehicles and archival storage, museums, and valuable documents.

Halon (including Halon 1211 and Halon 1301), are gaseous agents that inhibit the chemical reaction of the fire. Classes B:C for 1301 and smaller 1211 fire extinguishers (2.3 kg; under 9 lbs) and A:B:C for larger units (9–17 lb or 4.1–7.7 kg). Halon gases are banned from new production under the Montreal Protocol, as of January 1, 1994, as its properties contribute to ozone depletion and long atmospheric lifetime, usually 400 years. Halon may be recycled and used to fill newly manufactured cylinders, however, only Amerex continues to do this. The rest of the industry has moved to halon alternatives, nevertheless, Halon 1211 is still vital to certain military and industrial users, so there is a need for it. Halon was completely banned in Europe and Australia, except for critical users like law enforcement and aviation, resulting in stockpiles either being destroyed via high heat incineration or being sent to the United States for reuse. 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. Halon 2402 is a liquid agent (dibromotetrafluoroethane) which has had limited use in the West due to its higher toxicity than 1211 or 1301. It is widely used in Russia and parts of Asia, and it was used by Kidde's Italian branch, marketed under the name "Fluobrene".

Halon replacements include HCFC Blend B (Halotron I), HFC-227ea (FM-200), HFC-236fa (FE-36), FK 5-1-2, and Stabilized BTP (Halotron BrX; 2-bromo-3,3,3-trifluoro-1-propene). Halotron-1 was approved by the FAA for use in aircraft cabins in 2010. Considerations for halon replacement include human toxicity when used in confined spaces, ozone depleting potential, and greenhouse warming potential. The three recommended agents meet minimum performance standards, but uptake has been slow because of disadvantages. Specifically, they require two to three times the concentration to extinguish a fire compared with Halon 1211. They are heavier than halon, require a larger bottle because they are less effective, and have greenhouse gas potential. Research continues to find better alternatives.

Dry powder and metal fire extinguishers

There are several class D fire extinguisher agents available; some will handle multiple types of metals, others will not.

Sodium chloride (Super-D, Met-L-X, M28, Pyrene Pyromet) contains sodium chloride salt, which melts to form an oxygen-excluding crust over the metal. A thermoplastic additive such as nylon is added to allow the salt to more readily form a cohesive crust over the burning metal. Useful on most alkali metals including sodium and potassium, and other metals including magnesium, titanium, aluminum, and zirconium. Not to be used for lithium fires as lithium can react with NaCl to form LiCl and Na which will continue burning.

Copper-based (Copper Powder Navy 125S) developed by the U.S. Navy in the 1970s for hard-to-control lithium and lithium-alloy fires. The 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, Chubb Pyromet) contains dry graphite that smothers burning metals. The 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) is 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.

Ternary eutectic chloride (T.E.C.) dry powder is a dry powder invented in 1959 by Lawrence H Cope, a research metallurgist working for the UK Atomic Energy Authority, and licensed to John Kerr Co. of England. It consists of a mixture of three powdered salts: sodium, potassium and barium chloride. T.E.C. forms an oxygen-excluding layer of molten salt on the metal's surface. Along with Met-L-X (sodium chloride), T.E.C has been reported to be one of the most effective agents for use on sodium, potassium, and NaK fires, and is used specifically on atomic metals like uranium and plutonium as it will not contaminate the valuable metal unlike other agents. T.E.C. is quite toxic, due to the barium chloride content, and for this reason is no longer used in the UK, and was never used in the US aside from radioactive material handling glove boxes, where its toxicity was not an issue due their confined nature. T.E.C. is still widely used in India, despite toxicity, while the West uses chiefly sodium chloride, graphite, and copper types of powder and considers T.E.C. obsolete.

Fire extinguishing ball

Several modern "ball" or grenade-style extinguishers are available on the market. The modern version of the ball is a hard foam shell, wrapped in fuses that lead to a small black powder charge within. The ball bursts shortly after contact with flame, dispersing a cloud of ABC dry chemical powder which extinguishes the fire. The coverage area is about 5 m2 (54 sq ft). One benefit of this type is that it may be used for passive suppression. The ball can be placed in a fire-prone area and will deploy automatically if a fire develops, being triggered by heat. They may also be manually operated by rolling or tossing into a fire. Most modern extinguishers of this type are designed to make a loud noise upon deployment.

This technology is not new, however. From about 1880 glass "fire grenades" filled with a weak solution of common salt and ammonium chloride in water were popular. The addition of the salts was to prevent freezing, with ammonium chloride thought to be more effective in extinguishing flame. They were deployed by hurling them at the base of the fire. Containing only about one imperial pint (0.57 L), they were of limited use. Some later brands, such as Red Comet, were designed for passive operation and included a special holder with a spring-loaded trigger that would break the glass ball when a fusible link melted, or were sealed with wax to melt in contact with flame and release the contents. As was typical of this era, some glass extinguishers contained the toxic (but effective) carbon tetrachloride. These glass fire grenade bottles are sought after by collectors.

Non-cylindrical designs

Fire extinguisher pressure vessels have traditionally used cylindrical geometry. In 2019, Czech company Amplla received EN 3-7 certification for a flat, ring-shaped pressure vessel design. The unit measures approximately 80-90 mm in depth and contains 4-6 kg of ABC dry powder at 15 bar operating pressure.

Condensed aerosol fire suppression

Condensed aerosol fire suppression is a particle-based form of fire extinction similar to gaseous fire suppression or dry chemical fire extinction. As with gaseous fire suppressants, condensed aerosol suppressants use clean agents to suppress the fire. The agent can be delivered by means of mechanical operation, electric operation, or combined electro-mechanical operation. To the difference of gaseous suppressants, which emit only gas, and dry chemical extinguishers, which release powder-like particles of a large size (25–150 μm) condensed aerosols are defined by the National Fire Protection Association as releasing finely divided solid particles (generally <10 μm), usually in addition to gas.

Whereas dry chemical systems must be directly aimed at the flame, condensed aerosols are flooding agents and therefore effective regardless of the location and height of the fire. Wet chemical systems, such as the kind generally found in foam extinguishers, must, similarly to dry chemical systems, be sprayed directionally, onto the fire. Additionally, wet chemicals (such as potassium carbonate) are dissolved in water, whereas the agents used in condensed aerosols are microscopic solids.

Experimental techniques

In 2015, researchers from George Mason University announced that high volume sound with low bass frequencies in the 30 to 60 hertz range drives oxygen away from the combustion surface, extinguishing the fire, a principle was previously tested by the Defense Advanced Research Projects Agency (DARPA). One proposed application is to extinguish fires in outer space, with none of the clean-up required for mass-based systems.

Another proposed solution for fire extinguishers in space is a vacuum cleaner that extracts the combustible materials.

Maintenance

Most countries in the world require regular fire extinguisher maintenance by a competent person to operate safely and effectively, as part of fire safety legislation. Lack of maintenance can lead to an extinguisher not discharging when required, or rupturing when pressurized. Deaths have occurred, even in recent times, from corroded extinguishers exploding.

In the United States, state and local fire codes, as well as those established by federal agencies such as the Occupational Safety and Health Administration, are generally consistent with standards established by the National Fire Protection Association (NFPA). They commonly require, for fire extinguishers in all buildings other than single-family dwellings, inspections every 30 days to ensure the unit is pressurized and unobstructed (done by an employee of the facility) and an annual inspection and service by a qualified technician. Some jurisdictions require more frequent service. The servicer places a tag on the extinguisher to indicate the type of service performed (annual inspection, recharge, new fire extinguisher). Hydrostatic pressure testing for all types of extinguishers is also required, generally every five years for water and CO2 models up to every 12 years for dry chemical models.

Recently the NFPA and ICC voted to allow for the elimination of the 30-day inspection requirement so long as the fire extinguisher is monitored electronically. According to NFPA, the system must provide record keeping in the form of an electronic event log at the control panel. The system must also constantly monitor an extinguisher's physical presence, internal pressure and whether an obstruction exists that could prevent ready access. In the event that any of the above conditions are found, the system must send an alert to officials so they can immediately rectify the situation. Electronic monitoring can be wired or wireless.

In the UK, three types of maintenance are required:

Basic service: All types of extinguisher require a basic inspection annually to check weight, externally validate the correct pressure, and find any signs of damage or corrosion. Cartridge extinguishers are to be opened up for internal inspection, and to have the weight of the cartridge tested. Labels must be inspected for legibility, and where possible, dip tubes, hoses and mechanisms must be tested for clear, free operation.