There are three basic types of fire extinguishers that are made in order to put out fires of all sorts. Water based fire extinguishers are filled with pressurized water to put out fire from combustible fires originating from wood or paper. Dry chemical fire extinguishers are filled with a dry chemical that smothers fires originating from gas or oil. Water will not put out these fires, and would in fact make them worse. Carbon dioxide fire extinguishers are used to extinguish electrical fires. It is important to have the correct fire extinguisher on hand to quickly put out fires that may occur.
Dry chemical extinguishers are sold under the heading of Class B. Class B fire extinguishers are made to put out fires from combustible liquids, such as gasoline, kerosene, grease and oil. Each class B, or dry chemical, fire extinguisher will come with a numerical rating that indicates the number of square feet of fire it can effectively put out. Dry chemical extinguishers can contain a number of dry chemicals, including contain mono-ammonium phosphate, sodium bicarbonate, or potassium bicarbonate solution. These dry chemicals suffocate these types of fires.
Fire extinguishers filled with carbon dioxide or another non-conductive agent are appropriate for putting out electrical fires. Class C fire extinguishers are made for putting out fires originating from appliances, wiring, circuit breakers and outlets. Though mainly used for electrical fires, these fire extinguishers can also be used to put out fires from combustible liquids. However, they should never be used to put out fires from wood or paper unless there is no other alternative.
There are a few things to keep in mind when using fire extinguishers. Carbon dioxide fire extinguishers are under considerable pressure. They will expel their contacts in about 20 seconds whereas it takes a full minute for dry chemical extinguishers to expel their contents. One danger is that carbon dioxide fire extinguishers have the ability to spread the burning contents around the area. Also, as the carbon dioxide expels, it will rapidly cool the handle, and can cause frostbit to the handler if caution is not taken. Dry chemical fire extinguishers, though effective at putting out electrical fires, can cause damage to electrical components when they are exposed.
Place the fire extinguisher that best suits the area where it is placed. It is important that the area is equipped with the fire extinguisher best able to handle a fire that might erupt, otherwise it will not be of service during a real emergency. If you are unsure as to which fire extinguisher is best for your space, check your company and building regulations. You can always place both kinds in an area, just be sure they are adequately labeled so that during an emergency the proper one can be quickly identified to put out a fire.