A Class A fire extinguisher is designed to extinguish fires involving ordinary combustibles such as wood, paper, cloth, rubber, and many plastics. The rating is based on the type of material that the extinguisher is effective against. Class A extinguishers typically use water or a foam agent to extinguish fires.
Class A fire extinguishers use a combination of water, monoammonium phosphate, and ammonium sulfate to smother the fire. These agents work by cutting off the oxygen supply to the fire, which causes it to go out. Class A fire extinguishers are typically used in homes, offices, and other buildings where ordinary combustibles are present. They are not recommended for use on fires involving flammable liquids, gases, or electrical equipment, as the water or foam agents can be dangerous or ineffective on those types of fires. They can also be known as “water type” or “regular extinguisher”.