A fire extinguisher is an active fire protection device used to extinguish or control a fire, often in emergency situations. Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel, containing a chemical agent which can be discharged to extinguish a fire.
Fire extinguishers have been a major part of fire prevention. The first, primitive fire extinguishers were most likely created shortly after fire was discovered. They come in a wide variety of sizes and shapes. Their greatest benefit is the convenience and the safety that they provide.
The typical steps for operating a fire extinguisher (described by the acronym "PASS") are the following:
There are various types of extinguishers, which are used for different types of fires; using the wrong type can worsen the fire hazard, but using the right one can create a better situation. However, fire extinguishers are not a substitute for trained fire-fighting professionals with state-of-the-art equipment. They are, rather, a supplement to be used as a prevention measure—but once the fire is out of control, the safest recourse is to quickly leave the hazard area and call the fire department.
The modern fire extinguisher was invented by British Captain George William Manby in 1818; it consisted of a copper vessel with 3 gallons (13.6 liters) of pearl ash (potassium carbonate) solution contained within compressed air.
The soda-acid extinguisher was invented in the nineteenth century, which was comprised of a cylinder with 1 or 2 gal of water with sodium bicarbonate mixed into it. A vial was suspended in the cylinder containing concentrated sulphuric acid. Depending on the type of extinguisher, the vial of acid could be broken in one of two ways. One way 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 pressurized the water. The pressurized water was forced from the canister through a nozzle or short length of hose.
Around 1912, Pyrene invented the carbon tetrachloride, or 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) sizes. The CTC vaporized and extinguished the flames by chemical reaction. The extinguisher was suitable for liquid and electrical fires, and was popular in motor vehicles for the next 60 years. However, the vapor and combustion by-products were highly toxic, and could cause death in confined spaces.
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.
|Foam||Solid blue||Red with a blue band||A||B|
|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.
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 at least 5 percent 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.
|Type||Old Code||BS EN 3 Color 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 (Limited)||B||C||E|
|Carbon Dioxide CO2||Black||Red with a Black panel above the operating instructions||A (Limited)||B||E|
|Halon||Emerald Green||Pre-03- Signal red with a green panel||A||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 EN3-4) and inability to pass this test makes it compulsory to add a special label (pictogram) indicating the inability to isolate the user from a live electric source.
There is no official standard in the United States for the color of fire extinguishers, though they are typically red, except for Class D extinguishers, which are usually yellow. 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. No official pictogram exists for Class D extinguishers, though training manuals sometimes show a drill press with shavings burning underneath. The types of fires and additional standards are described in NFPA 10: Standard for Portable Fire Extinguishers.
|Fire Class||Geometric Symbol||Pictogram||Intended Use|
|A||Green Triangle||Garbage can and wood pile burning||Ordinary combustibles|
|B||Red Square||Gasoline can with a burning puddle||Flammable liquids|
|C||Blue Circle||Electric plug with a burning outlet||Energized electrical equipment|
|D||Yellow Star||N/A||Combustible metals|
|K||Black Hexagon||Pan burning||Cooking oils|
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.
Fire extinguishers are typically 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 (size/UL rating depending on type of vehicle and cargo, ie. fuel tankers typically must have a 20lb. when most others can carry a 5lb.).
Varying classes of competition vehicles require fire extinguishing systems, the simplest requirements being a 1A10B.C.E. hand-held portable extinguisher mounted to the interior of the vehicle.
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:
All links retrieved April 10, 2017.
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