A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not designed 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 handheld cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire.
There are two main types of fire extinguishers: Stored pressure and generated pressure. 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 are pressurized with air. Stored pressure are the most common types of fire extinguishers. Cartridge-operated extinguishers, contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the agent. These types as are 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 an reasonable amount of time. Unlike stored pressure types, these extinguishers utilize compressed carbon dioxide instead of nitrogen, although nitrogen cartridges are used on low temperature (-60 rated) models. Cartridge operated types are available in dry chemical and dry powder in the US and water, wetting agent, foam, and dry powder(ABC, BC, or D) in the rest of the world.
Fire extinguishers are further divided into handheld and cart-mounted, also called wheeled extinguishers. Handheld extinguishers weight from 2 to 30 pounds (1 to 14 kilograms), and are hence easily portable by hand. They exist in both stored- and generated-pressure types and contain all types of suppressants. Cart-mounted units typically weigh 50+ pounds (23+ kilograms), are cartridge-operated, and typically contain either dry chemical, Purple-K, foam, Halon, Halotron-1 or CO2. Wheeled models are most commonly found at construction sites, airport runways, heliports, and temporary landing sites.
The first automatic 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 litres) of pearl ash (potassium carbonate) solution contained within compressed air.
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.
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 bung that held the vial closed. Once the acid was mixed with the bicarbonate solution, carbon dioxide gas was expelled and thereby pressurize 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.
The chemical foam extinguisher was invented around 1905 by Alexander Laurant of Russia, who first used it to extinguish a pan of burning naptha. It works and looks similar to the soda-acid type, but the inner parts are different. The main tank contains a solution of water, foam compound (usually made from licorice root) and sodium bicarbonate. A cylindrical metal or plastic chamber holds about a quart and a half of 13% aluminum sulfate and is capped with a lead cap. When the unit is turned over, the chemicals mix, producing CO2 gas. The licorice causes some of the CO2 bubbles to become trapped in the liquid and is discharged on the fire as a thick whitish-brown foam.
Around 1912 Pyrene invented the carbon tetrachloride (CTC) extinguisher, which expelled the liquid from a brass or chrome container by a handpump; 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. A further variety consisted of a glass bottle "bomb" filled with the liquid that was intended to be hurled at the base of a fire. The CTC vaporized and extinguished the flames by creating a dense, oxygen-excluding blanket of fumes, and to a lesser extent, inhibiting the chemical reaction. The extinguisher was suitable for liquid and electrical fires, and was popular in motor vehicles for the next 60 years. 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.
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 to extinguisher the previously difficult to extinguish fires in telephone switchboards. It consisted of a tall metal cylinder containing 7.5 lbs. of CO2 with a wheel valve and a woven brass, cotton covered hose, with a composite funnel-like horn as a nozzle. CO2 is still popular today as it is a ozone-friendly clean agent and is useful for a extinguishing a person who is on fire, hence its widespread use in film and television.
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 CO2 cartridge. 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.
Halon 1211 came over to the US in the 1970s, and had been used there since the late 40s or early 50s. Halon 1301 had been developed by DuPont and the US Army in 1954. Both 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 severly restricted its use, but it is still widely available in North America, the Middle East, and Asia.
|Foam||Solid blue||Red with a blue band||A||B|
|Dry chemical (powder)||Red with a white band||A||B||C||E|
|Carbon dioxide||Red with a black band||A (limited)||B||C||E||F|
|Vapourising liquid (not halon)||Red with a yellow band||A||B||C||E|
|Wet chemical||Solid oatmeal||Red with an oatmeal band||A||F|
In Australia, yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted.
|Type||Old Code||BS EN 3 Colour Code||Fire Class|
|Water||Signal Red||Signal Red||A|
|Foam||Cream||Red with a Cream panel above the operating instructions||A||B||sometimes E|
|Dry powder||French Blue||Red with a Blue panel above the operating instructions||A||B||sometimes C||E|
|Carbon dioxide CO2||Black||Red with a Black panel above the operating instructions||B||E|
|Wet chemical||No F Class||Red with a Canary Yellow panel above the operating instructions||A||F|
|Class D powder||French Blue||Red with a Blue panel above the operating instructions||D|
The UK recognizes six fire classes. Class A fires involve organic solids such as paper and wood. Class B fires involve flammable liquids. Class C fires involve flammable gases. Class D fires involve metals, Class E fires involve live electrical items and Class F fires involve cooking fat and oil. Fire extinguishing capacity is rated by fire class using numbers and letters such as 13A, 55B. EN 3 does not recognize a separate E class - this is an additional feature requiring special testing (dielectric test per EN 3-7:2004) and NOT passing this test makes it compulsory to add a special label (pictogram) indicating the inability to isolate the user from a live electric source.
In the UK the use of Halon gas is now illegal except under certain situations.
|Fire Class||Geometric Symbol||Pictogram||Intended Use||Mnemonic|
|A||Green Triangle||Garbage can and wood pile burning||Ordinary solid combustibles||Think A for anything that leaves ash|
|B||Red Square||Gasoline can with a burning puddle||Flammable liquids and gases||Think B for anything in a barrel - gas, oil, etc.|
|C||Blue Circle||Electric plug with a burning outlet||Energized electrical equipment||Think C for current|
|D||Yellow Pentagram (Star)||Burning Gear and Bearing||Combustible metals|
|K||Black Hexagon||Pan burning||Cooking oils and fats||Think K for kitchen|
The Underwriters Laboratories rate fire extinguishing capacity in accordance with UL/ANSI 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.
Powder based agent that extinguishes by separating the four parts of the fire tetrahedron. It prevents the chemical reaction between heat, fuel and oxygen and halts the production of fire sustaining "free-radicals", thus extinguishing the fire.
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.
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.
There is no all-encompassing fire code in the United States. Generally, most municipalities (by adoption of the International Fire Code) require inspections every 30 days to ensure the unit is pressurized and unobstructed (done by an employee of the facility) and an annual inspection by a qualified technician. 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 National Fire Protection Association 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 as well:
The extinguisher is emptied of its chemical and presure to check for proper operation. All components are disassembled, inspected, cleaned, lubed, or replaced if defective. Liquid agents are replaced at this time, dry agents may be re-used in in good condition, halon is recovered and re-used, but CO2 is simply discharged to the atmosphere. Extinguisher is then re-filled and recharged, after a "verification of service" collar is placed around the cylinder neck. It is impossible to properly install or remove a collar without depressurizing the extinguisher, although '''many fly-by-night companies either cut and tape these, cut and dab a little crazy-glue on the bottom of the cut area on the collar or put the largest one possible on so that it slips over the valve-watch out!! Note: Cartridge-operated extinguishers should be visually examined, but do not require a verification of service collar.
Extinguishers installed on vehicles-every 5 years regardless or type.
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. CO2 types have the test date, company's ID, etc. 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 maintenenace 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.
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 (Ex. 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 ID 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 ID sign for each extinguisher on the site.
Fire extinguisher signs are mounted above or to the side of the extinguisher they relate to.
Most licensing authorities have regulations describing the standard appearance of these signs (e.g. text height, pictographs used and so on).
Photo-luminescent fire extinguisher signs are made of a polymer 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.
Photo-luminescent signs are sometimes mis-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. However, many fire extinguishers and extinguisher mounting posts have strips of reflective adhesive tape placed on them to facilitate their location in situations where only emergency lighting or flashlights are available.
Older luminescent signs sometimes used a radioactive tritium source to energise the polymeric material. This source could pose a hazard when such signs are dismantled or damaged. Modern photoluminescent materials are, however, not radioactive.