There are two types of fire extinguishers that use a dry chemical. One is called “multi-purpose dry chemical” and uses ammonium phosphate as the extinguishing agent, which is effective on “A,” “B,” and “C” class fires. This chemical is corrosive and must be scrubbed from surfaces after use. These types of extinguishers are very common and are found in schools, homes, hospitals and offices. Sodium bicarbonate is used in extinguishers known as “regular dry chemical,” which are capable of handling “B” and “C” class fires. These extinguishers are found in garages, kitchens and laboratories. Sodium bicarbonate is easy to clean and non-toxic.
These extinguishers contain liquid CO2 that is expelled as a gas. They are effective against “B” and “C” class fires. Unlike other chemicals, CO2 does not leave a harmful residue and is environmentally friendly. It also poses very little danger to electronics and is effectively employed in laboratories, computer rooms, and other areas with sensitive equipment.
These extinguishers are most suited for “A” class fires. However, they cannot be used in “B,” “C” or “D” class fires. In “B” and “D” class fires, the water will spread the flames. In a “C” class fire, the water is conductive and poses a risk of electric shock to the operator. However, the misting nozzle of a “Water Mist” extinguisher breaks up the stream of deionized water so that there is no conductive path back to the operator. Since the agent used is water, these types of extinguishers are inexpensive and environmentally friendly.
Wet Chemical Fire Extinguishers
These devices are designed to combat “K” class fires and commonly use potassium acetate. They are appropriately employed in commercial kitchens and restaurants, especially around deep fryers. The chemical is emitted as a fine mist that does not cause grease to splash onto other surfaces. They can also be used in “A” class fires.