Powder Fire Extinguishers are dry substances packed in high-pressurized cylinders. Powder Fire Extinguishers are often seen in a home, workshops, kitchens and anywhere combustible solids and liquids are. This type of fire extinguisher is also recommended for electrical fires.
At present, there are about 4 types of powdered chemicals used in putting out fires.
Ammonium Phosphate is recommended for type ‘A’ , ‘B’ and ‘C’ fires. This chemical is sprayed on a fiery surface in powder form and at 350° melts, easily spreading over to smother the fire. Since a chemical reaction due to heated temperature causes it to liquefy, it is considered more corrosive than other extinguisher in powder form.

Sodium Bicarbonate or baking soda is used in types ‘B’ and ‘C’ fires only. When sprayed on fire, the sodium bicarbonate goes through a decompression reaction which in turn results to the emission of carbon dioxide. This is an indirect way of releasing carbon dioxide to neutralize the oxygen that hastens the spread of the flames.

Potassium Bicarbonate is like wise used on type ‘B’ and ‘C’ fires. Unlike the baking soda, potassium bicarbonate when used as a fire extinguisher is 2 times more effective when used on oil and gas fires. Potassium bicarbonate is the only flame retardant certified for use in airplane fires since it does not react to alcohol and successfully contains and stops fire from spreading in the fastest time possible.  

Potassium Bicarbonate and Urea complex also known as ammonium bicarbonate was once used as a fire-proofing coating. Now it effectively puts out fires through its ability to break down into smaller parts to spread itself. It coats the area and suppresses the flame until it has died out.

Special powder fire extinguishers are used for type ‘D’ fires. The L2 is highly recommended for flames involving combustible metals. Unlike some powdered chemicals used as retardants, L2 has no adverse reaction to combustible metals.