Fire extinguisher

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A stored-pressure fire extinguisher made by Amerex FireExtinguisherABC.jpg
A stored-pressure fire extinguisher made by Amerex

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 brigade. Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel containing an agent that can be discharged to extinguish a fire. Fire extinguishers manufactured with non-cylindrical pressure vessels also exist but are less common.

Contents

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 U.S. and in water, wetting agent, foam, dry chemical (classes ABC and B.C.), and dry powder (class D) types in the rest of the world.

Wheeled fire extinguisher and a sign inside a parking lot Wheeled fire extinguisher.jpg
Wheeled fire extinguisher and a sign inside a parking lot

Fire extinguishers are further divided into handheld and cart-mounted (also called wheeled extinguishers). Handheld extinguishers weigh from 0.5 to 14 kilograms (1.1 to 30.9 lb), and are hence, easily portable by hand. Cart-mounted units typically weigh more than 23 kilograms (51 lb). These wheeled models are most commonly found at construction sites, airport runways, heliports, as well as docks and marinas.

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.

The modern dry powder 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.

Thomas J Martin, a Black inventor, was awarded a patent for the Fire Extinguisher on March 26, 1872. His invention is listed in the U. S. Patent Office in Washington, DC under patent number115,603.

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 CO2 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 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. [2]

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. [3]

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. [4] 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 mechanical foam types). Special versions were made for rough service, and vehicle mounting, known as apparatus of fire department types. Key features were a screw-down stopper that kept the liquids from mixing until it was manually opened, carrying straps, a longer hose, and a shut-off nozzle. Fire department types were often private label versions of major brands, sold by apparatus manufacturers to match their vehicles. Examples are Pirsch, Ward LaFrance, Mack, Seagrave, etc. These types are some of the most collectable extinguishers as they cross into both the apparatus restoration and fire extinguisher areas of interest.

In 1910, The Pyrene Manufacturing Company of Delaware filed a patent for using carbon tetrachloride (CTC, or CCl4) to extinguish fires. [5] 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. [6] 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 (0.57 l) capacity but was also available in up to 2 imperial gallons (9.1 l) size. As the container was unpressurized, it could be refilled after use through a filling plug with a fresh supply of CTC. [7]

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 extinguishers 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, [8] formerly used as a chemical weapon.

The carbon dioxide (CO2) 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 pounds (3.4 kg) of CO2 with a wheel valve and a woven brass, cotton covered hose, with a composite funnel-like horn as a nozzle. [9] CO2 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. [10] 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.

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. [11] [12] It consisted of a copper cylinder with an internal CO2cartridge. 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, 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. Manually applied dry agents such as graphite for class D (metal) fires had existed since WWII, but it wasn't until 1949 that Ansul introduced a pressurized extinguisher using an external CO2 cartridge to discharge the agent. Met-L-X (sodium chloride) was the first extinguisher developed in the US, with graphite, copper, and several other types being developed later.

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.

In the 1970s, Halon 1211 came over to the United States 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. Less severe restrictions have been implemented in the United States, the Middle East, and Asia. [13] [14]

Classification

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

Australia and New Zealand

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

TypeBand colour Fire classes (brackets denote sometimes applicable)
ABCDEF
WaterSignal redA
Wet chemicalOatmealAF
FoamUltramarine blueAB
Dry chemicalWhiteABCE
Dry powder (metal fires)Lime greenD
Carbon dioxideBlack(A)BE
Vaporizing liquid (non-halon clean agents)Golden yellowABCE
Halon No longer producedABE

In Australia, yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted, this is due to the ozone-depleting nature of halon. [15]

United Kingdom

A British fire extinguisher with ID sign, call point and fire action sign Fire extinguisher with ID sign, call point and fire action sign.JPG
A British fire extinguisher with ID sign, call point and fire action sign

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

The UK recognises six fire classes: [16]

Class E has been discontinued, but covered fires involving electrical appliances. 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.

TypeOld codeBS EN 3 colour code Fire classes
(brackets denote sometimes applicable) [17]
ABCDEF
WaterSignal redSignal redA
FoamCreamRed with a cream panel above the operating instructionsAB
Dry powderFrench blueRed with a blue panel above the operating instructionsABCE
Carbon dioxide, CO2BlackRed with a black panel above the operating instructionsBE
Wet chemicalN/ARed with a canary yellow panel above the operating instructionsA(B)F
Class D powderFrench blueRed with a blue panel above the operating instructionsD
Halon 1211/BCFEmerald greenNo longer in general useABE

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. [18]

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

EN3 does not recognise a separate electrical class - however there is an additional feature requiring special testing (35 kV dielectric test per EN 3-7:2004). A powder or CO2 extinguisher will bear an electrical pictogramme as standard signifying that it can be used on live electrical fires (given the symbol E in the table). If a water-based extinguisher has passed the 35 kV test it will also bear the same electrical pictogramme – however, any water-based extinguisher is only recommended for inadvertent use on electrical fires.

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 classGeometric symbolPictogram Intended use Mnemonic
A Class A fire triangle.svg Fire type A.svg Ordinary solid combustiblesA for "Ash"
B Class B fire square.svg Fire type B.svg Flammable liquids and gasesB for "Barrel"
C Class C fire circle.svg Class C fire icon.svg Energized electrical equipmentC for "Current"
D Class D fire icon.svg Class D metal fire icon.svg Combustible metalsD for "Dynamite"
K Class K fire hexagon.svg Class K fire icon.svg Oils and fatsK for "Kitchen"

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.

Comparison of fire classes
AmericanEuropeanUKAustralian/AsianFuel/heat source
Class AClass AClass AClass AOrdinary combustibles
Class B Class B Class B Class B Flammable liquids
Class CClass CClass CFlammable gases
Class CUnclassifiedUnclassifiedClass EElectrical equipment
Class DClass DClass DClass DCombustible metals
Class KClass FClass FClass FCooking oil or fat

Installation

Automatic engine compartment fire extinguisher installed on a hybrid city bus. Automatic engine compartment fire extinguisher.jpg
Automatic engine compartment fire extinguisher installed on a hybrid city bus.

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.

A dedicated trolley loaded with extinguishers ready to move where needed for rapid use Fire extinguisher trolley (167818050).jpg
A dedicated trolley loaded with extinguishers ready to move where needed for rapid use

The height limit for installation, as determined by the National Fire Protection Association (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. [19] NZ Transport Agency recommends [20] that all company vehicles carry a fire extinguisher, including passenger cars.

Fire extinguishers mounted inside aircraft engines are called extinguishing bottles or fire bottles. [21]

Types of extinguishing agents

Dry chemical

This is a powder-based agent that extinguishes by separating the four parts of the fire tetrahedron. It prevents the chemical reactions involving heat, fuel, and oxygen (combustion), 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.

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.

Water types

Cools burning material. Very effective against fires in furniture, fabrics, etc. (including deep-seated fires), but can be safely used only in the absence of electricity.

Wet chemical and water additives

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 (an alkali 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).

  • 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 (−40 °C). Has no appreciable effect on extinguishing performance. Can be glycol based or loaded stream, see below.
  • Loaded Stream An alkali metal salt solution added to water to lower its freezing point to about −40 °F (−40 °C). Loaded stream is basically concentrated wet chemical, discharged through a straight stream nozzle, intended for class A fires. In addition to lowering the freezing point of the water, loaded stream also increases penetration into dense class A materials and will give a slight class B rating (rated 1-B in the past), though current loaded stream extinguishers are rated only 2-A. Loaded Stream is very corrosive; extinguishers containing this agent must be recharged annually to check for corrosion.

Halons, Halon-replacement clean agents and carbon dioxide

Clean agents extinguish fire by displacing oxygen (CO2 or inert gases), removing heat from the combustion zone (Halotron-1, FE-36, Novec 1230) or inhibiting the chemical chain reaction (Halons). 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 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".

Class D dry powder and other agents for metal fires

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

TMB was used experimentally by the US Air Force, specifically with regard to B-52 engine assemblies, and was tested in modified 10-gallon wheeled CBM extinguishers. Other agents were added to suppress the methanol flare up, such as chlorobromomethane (CBM), Halon 2402, and Halon 1211, with varied success. Halon 1211 was the most successful, and the combined TMB pressurized with halon 1211 and nitrogen was called Boralon was used experimentally by the Los Alamos National Laboratory for use on atomic metals, using sealed cylinder extinguishers made by Metalcraft and Graviner which eliminated the moisture contamination problem. TMB/Boralon was abandoned in favor of more versatile agents, though it is still mentioned in most US firefighting literature. [31]

Buffalo marketed a 2.5-gallon and 1-quart extinguisher using M-X liquid discharged through a low-velocity shower head-type nozzle, but it was met with limited success, as it was going up against Ansul's Met-L-X, which could be used on more types of metals and was non-combustible. M-X had the advantage of being easy to recharge and non-corrosive since it was oil-based, but production did not last long due to its limited applications.

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.

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. [35]

This technology is not new, however. In the 1800s, glass fire grenades filled with suppressant liquids were popular. These glass fire grenade bottles are sought by collectors. [36] 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. As was typical of this era, some glass extinguishers contained the toxic carbon tetrachloride.

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. [37]

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). [38] One proposed application is to extinguish fires in outer space, with none of the clean-up required for mass-based systems. [39]

Another proposed solution for fire extinguishers in space is a vacuum cleaner that extracts the combustible materials. [40]

Maintenance

An empty fire extinguisher which was not replaced for years. Fire7041.JPG
An empty fire extinguisher which was not replaced for years.

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). [41] 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:

In the United States, there are 3 types of service:

Note: these are the required intervals for normal service conditions, if the extinguisher has been exposed to excessive heat, vibration, or mechanical damage it may need to be tested sooner.

The agent is emptied and depressurized and the valve is removed. After a thorough internal and external visual inspection, the cylinder is filled with water, placed inside a safety cage, and pressurized to the specified test pressure (varies with the type, age, and cylinder material) for the specified time period. If no failure, bulges, or leaks are detected, the cylinder passes. The cylinder is then emptied of water and thoroughly dried, and labeled with the test date and company that performed the test. CO2 types have the test information stamped on the cylinder, all other types get a sticker on the back of the cylinder. Once dry, the units are recharged. Unlike the UK, the US does not rebuild extinguishers and replace valves at specific intervals unless parts are found to be defective, with the exception of halon. Halon types are often given new o-rings and valve stems at every internal maintenance to minimize any leakage potential.

OEM equipment must be used for replacement parts for the extinguisher to maintain its UL rating. If parts are unavailable, replacement is recommended, keep in mind extinguishers have a projected service life of about 25–35 years, although many are of such quality that they can outlast this, but realize that science is ever-changing, and something that was the best available 30 years ago may not be acceptable for modern fire protection needs.

Vandalism and extinguisher protection

A fire extinguisher stored inside a cabinet mounted to a wall Fire Extinguisher.JPG
A fire extinguisher stored inside a cabinet mounted to a wall
Heavy-duty CO2-powered fire extinguisher on standby at a temporary helicopter landing site Aa big fire extinguisher 00.jpg
Heavy-duty CO2-powered fire extinguisher on standby at a temporary helicopter landing site

Fire extinguishers are sometimes a target of vandalism in schools and other open spaces. Extinguishers are occasionally partially or fully discharged by a vandal, impairing the extinguisher's actual fire-fighting abilities.

In open public spaces, extinguishers are ideally kept inside cabinets that have glass that must be broken to access the extinguisher, or which emit an alarm siren that cannot be shut off without a key, to alert people the extinguisher has been handled by an unauthorized person if a fire is not present. This also alerts maintenance to check an extinguisher for usage so that it may be replaced if it has been used.

Fire extinguisher signs

Fire extinguisher identification signs are small signs designed to be mounted near a fire extinguisher, in order to draw attention to the extinguisher's location (e.g., if the extinguisher is on a large pole, the sign would generally be at the top of the pole so it can be seen from a distance). Such signs may be manufactured from a variety of materials, commonly self-adhesive vinyl, rigid PVC, and aluminum.

In addition to words and pictographs indicating the presence of a fire extinguisher, some modern extinguisher identification signs also describe the extinguishing agent in the unit, and summarize the types of fire on which it may safely be used.

Some public and government buildings are often required, by local legal codes, to provide an identification sign for each extinguisher on the site. [42]

Similar signs are available for other fire equipment (including fire blankets and fire hose reels/racks), and for other emergency equipment (such as first aid kits).

Placement of fire extinguisher signs

Most licensing authorities have regulations describing the standard appearance of these signs (e.g., text height, pictographs used and so on). [43]

Photoluminescent fire extinguisher location signs

Photoluminescent fire extinguisher signs are made with nontoxic photoluminescent phosphor that absorbs ambient light and releases it slowly in dark conditions – the sign "glows in the dark". Such signs are independent of an external power supply, and so offer a low-cost, reliable means of indicating the position of emergency equipment in dark or smoky conditions. The luminance performance for life safety appliance location signs should meet the requirements of International Standard ISO 17398 so that the sign is not only excited at very low ambient light levels (25 lux), but also has effective luminance intensity and longevity, making the life-safety message conspicuous in the event of power failure, or if smoke obscures emergency ceiling lights. The Photoluminescent Safety Products Association (PSPA) has guidance classifications for luminance performance to help users with applications under "International Maritime Organization Emergency Equipment and Life-saving Appliance Location Requirements," and worldwide industrial fire-safety management requirements.

Photo-luminescent signs are sometimes wrongfully described as being reflective. A reflective material will only return ambient light for as long as the light source is supplied, rather than storing energy and releasing it over a period of time. But, many fire extinguishers and extinguisher-mounting posts have strips of retroreflective adhesive tape placed on them to facilitate their location in situations where only emergency lighting or flashlights are available.

Selected patents

See also

Related Research Articles

Sodium Chemical element with atomic number 11

Sodium is a chemical element with the symbol Na (from Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell, which it readily donates, creating a positively charged ion—the Na+ cation. Its only stable isotope is 23Na. The free metal does not occur in nature, and must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust and exists in numerous minerals such as feldspars, sodalite, and rock salt (NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by the action of water from the Earth's minerals over eons, and thus sodium and chlorine are the most common dissolved elements by weight in the oceans.

Sodium chloride Chemical compound with formula NaCl

Sodium chloride, commonly known as salt, is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g/mol respectively, 100 g of NaCl contains 39.34 g Na and 60.66 g Cl. Sodium chloride is the salt most responsible for the salinity of seawater and of the extracellular fluid of many multicellular organisms. In its edible form of table salt, it is commonly used as a condiment and food preservative. Large quantities of sodium chloride are used in many industrial processes, and it is a major source of sodium and chlorine compounds used as feedstocks for further chemical syntheses. A second major application of sodium chloride is de-icing of roadways in sub-freezing weather.

Sodium bicarbonate Chemical compound

Sodium bicarbonate (IUPAC name: sodium hydrogen carbonate), commonly known as baking soda (mainly North America) or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion (HCO3). Sodium bicarbonate is a white solid that is crystalline, but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda (sodium carbonate). The natural mineral form is nahcolite. It is a component of the mineral natron and is found dissolved in many mineral springs.

Potassium chloride chemical

Potassium chloride is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt-like taste. KCl is used as a fertilizer, in medicine, in scientific applications, and in food processing, where it may be known as E number additive E508.

Potassium bicarbonate chemical compound

Potassium bicarbonate (also known as potassium hydrogen carbonate or potassium acid carbonate) is the inorganic compound with the chemical formula KHCO3. It is a white solid.

Potassium carbonate chemical compound

Potassium carbonate is the inorganic compound with the formula K2CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and glass.

Bromotrifluoromethane, commonly known as Halon 1301, R13B1, Halon 13B1 or BTM, is an organic halide with the chemical formula CBrF3. It is used for fire suppression. Relative to other fire suppressing agents, such as bromochloromethane, it is far less toxic.

Fire triangle model for understanding the necessary ingredients for most fires

The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires.

This is a glossary of firefighting equipment.

Purple-K, also known as PKP, is a dry-chemical fire suppression agent used in some dry chemical fire extinguishers. It is the second most effective dry chemical in fighting class B fires after Monnex, and can be used against some energized electrical equipment fires. It has about 4–5 times more effectiveness against class B fires than carbon dioxide, and more than twice that of sodium bicarbonate. Some fire extinguishers are capable of operation in temperatures down to −54 °C or up to +49 °C. Dry chemical works by directly inhibiting the chemical chain reaction which forms one of the four sides of the fire tetrahedron. To a much smaller degree it also has a smothering effect by excluding oxygen from the fire. "Dry chemical" extinguishers, such as Purple-K, are different from "dry powder" extinguishers that are used to fight Class D flammable metal fires.

Firefighting foam foam that is used for fire suppression

Firefighting foam is a foam used for fire suppression. Its role is to cool the fire and to coat the fuel, preventing its contact with oxygen, resulting in suppression of the combustion. Fire-fighting foam was invented by the Russian engineer and chemist Aleksandr Loran in 1902.

Fire class is a term used to denote the type of fire, in relation to the combustion materials, that has ignited. This affects the type of suppression or extinguishing materials that can be used. Class letters are often assigned to the different types of fire, but these differ between territories. There are separate standards in the United States, Europe, and Australia.

Compressed air foam system

A compressed air foam system (CAFS) is used in firefighting to deliver fire retardant foam for the purpose of extinguishing a fire or protecting unburned areas.

A twin-agent fire extinguishing system (TAFES) incorporates the benefits of dry chemical and foam. Most commonly used for AR-FF operations and in industrial areas with high class B hazards.

ABC dry chemical common firefighting chemical

Monoammonium phosphate, ABC Dry Chemical, ABE Powder, tri-class, or multi-purpose dry chemical is a dry chemical extinguishing agent used on class A, class B, and class C fires. It uses a specially fluidized and siliconized monoammonium phosphate powder. ABC dry chemical is usually a mix of monoammonium phosphate and ammonium sulfate, the former being the active one. The mix between the two agents is usually 40–60%, 60-40%, or 90-10% depending on local standards worldwide. The USGS uses a similar mixture, called Phos Chek G75F.

Commonly referred to as "Fast Flow" or "High Performance" extinguishers. Available in 13.2 lb (6.0 kg)., 20 lb (9.1 kg)., and 30 lb (14 kg). capacities and contain ABC Dry Chemical, Purple-K, or sodium bicarbonate. They are currently manufactured by Ansul in cartridge-operated form, along with Amerex, Badger and Buckeye stored pressure design.

Automatic fire suppression

Automatic fire suppression systems control and extinguish fires without human intervention. Examples of automatic systems include fire sprinkler system, gaseous fire suppression, and condensed aerosol fire suppression. When fires are extinguished in the early stages loss of life is minimal since 93% of all fire-related deaths occur once the fire has progressed beyond the early stages.

Read and Campbell Limited was a British manufacturer of firefighting equipment founded in 1881. The company was an early pioneer in the design and manufacture of portable fire extinguishers.

Condensed aerosol fire suppression

Condensed aerosol fire suppression is a particle-based form of fire extinction. It is similar to gaseous fire suppression. It employs a fire-extinguishing agent consisting of: very fine solid particles as well as gaseous matter. The condensed aerosol microparticles and effluent gases are generated by the exothermic reaction; the particles remain in vapor state until the process of being discharged from the device. Then, it is "condensed" and cooled within the device and discharged as solid particles.

Class B fire

In fire classes, a Class B fire is a fire in flammable liquids or flammable gases, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, or alcohols. For example, propane, natural gas, gasoline and kerosene fires are types of Class B fires. The use of lighter fluid on a charcoal grill, for example, creates a Class B fire. Some plastics are also Class B fire materials.

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