Fire extinguishers are divided into four classifications, according to the type of fire they are designed to eliminate. Extinguishers are available in individual classifications and combinations. Some also have a numerical rating to indicate the amount of fire the extinguisher can handle. There are many types of fire extinguishers, some more common than others.
Class A fire extinguishers are water extinguishers and are designed for fires involving paper, wood, cardboard and plastic.
Class B extinguishers work on fires caused by flammable or combustible fluids such as oil, kerosene, grease and gasoline.
Class C fire extinguishers are designed for fires involving electrical equipment.
Class D fires involve combustible metals, typically in chemical laboratories.
Dry-chemical fire extinguishers can be used for fires in class A, B and C. The dry chemicals are foam or powder of sodium bicarbonate, potassium bicarbonate or monoammonium phosphate.
Carbon dioxide fire extinguishers are suitable for class B and C fires, and unlike the dry-chemical types, they do not leave any damaging residue.
Halon gas extinguishers are good for using on electrical equipment, and they also do not leave residue.