FIRE EXTINGUISHER AND CLASSIFICATIONS
Fires and extinguishers are classified according to the type of fuel that is being consumed by the fire.
CLASS AFires involving the combustion of ordinary materials such as wood, cloth, paper, plastics etc. The extinguishers contain pressurized water or water based extinguishing agents.
Fires involving combustible or flammable liquids such as gasoline, kerosene and many chemical agents including gases.
Extinguishers contain carbon dioxide or a dry chemical extinguishing agent.
Fires involving energized electrical equipment such as appliances of all kinds, motors, computers etc.
Extinguishers contain carbon dioxide, Halon, dry chemical or liquid extinguishing agent.
When extinguishing electrical fires in or around sensitive equipment such as computers, a carbon dioxide extinguisher is preferred, as it does not leave any reside that will harm subsequent operation of the equipment
Fires involving combustible metals such as sodium, lithium, titanium, magnesium.
Extinguishing agent usually comes in dry powder form stored in a bucket.
Fires involving cooking fats & oil in commercial cooking.
Extinguishing agent comes as liquid chemical.
The ratings for Class “A” or “B” portable extinguishers are also accompanied by a numerical value which corresponds its extinguishing capacity.
CLASS A Fire extinguishers with a Class “A” ratings are effective against fires involving paper, wood, textiles and plastics. The primary chemical used to fight these fires is monoammonium phosphate, because of its ability to smother fires in these types of materials. To achieve the Class A rating, an extinguisher must be capable of extinguishing the wood crib, wood panel, and *excelsior fire tests. Ratings are based on the size of the crib, panel and excelsior fires that are repeatedly extinguished. The following dimensions are approximate sizes, supplied for informational purposes only.
|Rating||Wood Crib (Inches)||Wood Panel (Feet)||Excelsior (Pounds)|
CLASS B Fire extinguishers with a Class “B” ratings are effective against flammable liquid fires. These can be fires where cooking liquids, grease, oil, gasoline, kerosene, or paint have become ignited. Two commonly used chemicals are effective in fighting these types of fires. Monoammonium phosphate effectively smothers the fire, while sodium bicarbonate induces a chemical reaction which extinguishes the fire. To achieve the Class B rating, an extinguisher must repeatedly put out a flaming liquid fire. The rating is again based on the size of the fire extinguished.
|Rating||Pan Size (Sq. Ft.)||Gallons of Heptane|
CLASS CFire extinguishers with a Class C rating are suitable for fires in "live" electrical equipment. Both monoammonium phosphate and sodium bicarbonate are commonly used to fight this type of fire because of their non-conductive properties. To achieve the Class C rating, an extinguisher and contents must pass certain Electrical Conductivity measurements in accordance with UL 711 and UL 299.
All extinguisher ratings are shown on the extinguisher faceplate. Each extinguisher is rated with a letter (A, B, C, D or K) corresponding to the type of fire that it can be used on (see table above).
HOW TO CHOOSE A FIRE EXTINGUISHER
Some extinguishers are rated to be used on more than one type of fire. These combinations are AB, AC, BC and ABC, which can be used on those types of fires corresponding to their rating letters as defined above. The combination extinguishers usually contain dry or wet chemical extinguishing agents, water, or carbon dioxide.
Class C extinguishers do not have a numerical rating, as the fires that they are used for usually are made up of both Class A and B fires, thus requiring then to also carry an A orB rating. Class C only refers to the fact that the extinguishing medium is non-conducting and can be used on electrical fires in which the equipment is energized.
Class D extinguishers usually are specific to the metal that would potentially ignite. It only carries the letter rating to indicate the type of fire it is to be used on.
WHAT EACH TYPE OF EXTINGUISHER LOOKS LIKE
Generally, you can tell with a glance which type of extinguisher is hanging on the wall, or in the cabinet, just by looking at its shape. Check the labels of the extinguishers in your area and note the color and shape/size of the extinguisher. This may help if someone assists you in fighting a fire with the WRONG extinguisher (i.e. water on an electrical fire) - you can STOP them before they are injured or make matters worse!
ABC-rated multipurpose dry powder extinguishers are the most common on campus, particularly in the corridors of academic buildings. They are almost always RED in color and have either a long narrow hose or no hose (just a short nozzle). These extinguishersare very light (5-25 lbs total weight).
Water extinguishers are usually SILVER (chrome-metal) in color, have a flat bottom, have a long narrow hose, and are quite large (2-1/2 gallons).
CO2 (carbon dioxide) extinguishers are generally red (often yellow around aircraft or on military sites), have a LARGE "tapered" nozzle (horn), are VERY HEAVY (5-100 lbs. hand held or wheeled units)
CO2 Extinguishers are all high-pressure cylinders.
Care should be used not to drop a CO2 cylinder; if it is damaged pressure released can punch a hole through the nearest wall(s) and end up on the other side of the building! (The containers are quite sturdy, but don't abuse them.)
Note: CO2 extinguishers do not have pressure gauges and must be weighed to determine the exact amount of extinguishing agent inside.
WHEN TO USE AN EXTINGUISHER
Fires have the ability to burn quickly out of control. The only time that a portable extinguisher should be used to fight a fire is when:
Person should be familiar with the use of a fire extinguisher.
The extinguisher is readily available for immediate use (is near by) and is in good working order which is fully charged.
The extinguisher is suitable for the fire hazard being protected.
The fire is small enough to be controlled by the type of extinguisher present and the fire does not move from its originating position
The possibility that the fire will block your exit route does not exist.
If the above conditions can not be met, evacuate the area immediately and call your Fire Department.
HOW TO USE A PORTABLE FIRE EXTINGUISHER
The easiest way to remember how to use a portable fire extinguisher is to use the acronym PASS
- ....Pull the safety pin.
- ...aim the extinguisher nozzle at the base of the flames.
- ...squeeze the trigger while holding the extinguisher upright.
- ...sweep the extinguisher from side to side, covering the area of the fire with extinguishing agent.
WHAT TO DO AFTER USING AN EXTINGUISHER
After an extinguisher has been used, even just a little bit, you must report it to Management so that it can be recharged or possibly replaced. While CO2 and Halon extinguishers will generally hold their pressure after a slight discharge, BC and ABC rated DRY CHEMICAL extinguishers will usually NOT hold a charge after partial use. While the gauge may hold steady in the green immediately after a light use, check it the next day and you'll find the pressure gauge is on EMPTY! This is because upon use the dry powder permeates inside the seals or orings and allows the nitrogen carrier gas to escape over a period of time. You can't "test" an extinguisher and put it back in the cabinet! Any discharge of agent must be reported and the extinguisher must be recharged or possibly replaced!!!
HOW TO FIGHT SMALL FIRES
Extinguish ordinary combustibles by cooling the material below its ignition temperature and soaking the fibers to prevent re-ignition. Use pressurized water, foam or multi-purpose(ABC-rated) dry chemical extinguishers. DO NOT USE carbon dioxide or ordinary (BC-rated) dry chemical extinguishers on Class A fires.
Extinguish flammable liquids, greases or gases by removing the oxygen, preventing the vapors from reaching the ignition source or inhibiting the chemical chain reaction.
Foam, carbon dioxide, ordinary (BC-rated) dry chemical, multi-purpose dry chemical, and Halon extinguishers may be used to fight Class B fires.
Extinguish energized electrical equipment by using an extinguishing agent that is not capable of conducting electrical currents.
Carbon dioxide, ordinary (BC-rated) dry chemical, multi-purpose dry chemical and Halon fire extinguishers may be used to fight Class C fires. DO NOT USE water extinguishers on energized electrical equipment.
NOTE: Multipurpose (ABC-rated) chemical extinguishers leave a residue that can harm sensitive equipment, such as computers and other electronic equipment. Because of this, carbon dioxide or Halon extinguishers are preferred in these instances because they leave very little residue.
Extinguish combustible metals such as magnesium, titanium, potassium and sodium with dry powder extinguishing agents specially designated for the material involved. In most cases, they absorb the heat from the material, cooling it below its ignition temperature.
ENSURING EXTINGUISHERS ARE READY TO USE
Make sure that there are extinguishers available in your working area and know their locations. Make sure that the extinguishers are suitable for the hazards most likely to occur in that area.
Ensure that the safety pin is in place and attached by a plastic seal. If it is missing or has been tampered with, notify Management. Ensure that the extinguisher is full by "hefting" to test its weight (for carbon dioxide, CO2 extinguishers) and checking that the pressure gauge is in the acceptable (usually 100-175 lbs for water, some foam and dry chemical extinguishers) zone indicated on the gauge. If the extinguisher needs to be recharged, notify your Safety coordinator or Building Services.