There are various types of fire extinguishers that can be used when putting out a fire, and what type a person should use depends on what type of fire it is. There are four common types of fire classifications listed on extinguishers to help people better understand which one should be used. These types are also given numerical ratings to use as a guide for the amount of fire it can handle. For instance, the higher the numerical rating, the more fire extinguishing power it has.
Class A consists of solids or ordinary combustibles such as wood, paper, most plastics, or cardboard. Class B consists of flammable liquids such as kerosene, grease, gasoline, or oil. Class C consists of electrical components such as appliances, outlets, circuit breakers, or wiring. This class is not given a numerical rating, and the "C" means it is non-conductive. Class D consists of metals such as aluminum, magnesium, potassium, or sodium. They are often found in chemical laboratories and carry no numerical rating because they are designed solely for putting out fires involving of these materials.
Fire extinguishers will have one or more classes listed on them to explain what type of fire it's primarily used for. There are also four common types of material used in the extinguishers to put out a fire.
The water fire extinguisher is the least expensive but the most widely used. It is filled with water and pressurized with oxygen, and would typically be used for Class A fires. This particular variety would not be suitable for liquid or electrical fires.
The foam and dry chemical fire extinguishers are both dry chemical extinguishers. The foam type is more expensive than water but also more versatile. It is filled with a foam, such as aqueous film forming foam, and pressurized with nitrogen, and it would typically be used for Class A and B fires. It is not recommended for electrical fires.
The dry chemical extinguisher is considered a multipurpose device. It is filled with a dry powder, such as monoammonium phosphate, and is also pressurized with nitrogen, but can be used for Class A, B and C fires. Special powders are made available for Class D metal fires. Using a dry chemical extinguisher can leave sticky or corrosive residue that can be damaging to the surface that has been sprayed.
The CO2 fire extinguisher contains carbon dioxide, which is ideal for electrical fires and can also be used to extinguish some liquids and Class B and C fires. This extinguisher contains carbon dioxide and is highly pressurized. It does not leave a harmful residue, but it also has no post fire security, meaning that if it is not able to displace enough oxygen, the fire could re-ignite.
With four common types of fire extinguishers, choosing which one to use in putting out a fire would depend on the situation at hand. When purchasing one, the buyer should base his decision according to what type of fire he is most likely to encounter and what items he wishes most to protect.