Not all fires are the same. Different fuels create different fires and require different types of fire extinguishing agents.
Class A fires are fires in ordinary combustibles such as wood, paper, cloth, trash, and plastics.
Class B fires are fires in flammable liquids such as gasoline, petroleum oil and paint. Class B fires also include flammable gases such as propane and butane. Class B fires do not include fires involving cooking oils and grease.
Class C fires are fires involving energized electical equipment such as motors, transformers, and appliances. Remove the power and the Class C fire becomes one of the other classes of fire.
Class D fires are fires in combustible metals such as potassium, sodium, aluminum, and magnesium.
Class K fires are fires in cooking oils and greases such as animals fats and vegetable fats.
Some types of fire extinguishing agents can be used on more than one class of fire. Others have warnings where it would be dangerous for the operator to use a particular fire extinguishing agent.