Fire Extinguisher Types: A Complete Guide

Using the wrong type of fire extinguisher on a fire can be ineffective at best and dangerous at worst. Understanding the five primary extinguisher classes is essential for selecting the right tool for each hazard.

Class A extinguishers are designed for ordinary combustibles: wood, paper, cloth, trash, and most plastics. Water is the primary agent, which cools the fire below its ignition temperature. Class A is the most common type for home use.

Class B extinguishers are for flammable liquids: gasoline, oil, grease, paint, and petroleum gases. They work by smothering the fire with foam, carbon dioxide, or dry chemical agents that displace oxygen and interrupt the chemical reaction.

Class C extinguishers are for energized electrical equipment. Non-conductive agents like carbon dioxide and dry chemical are used because water-based agents would conduct electricity and pose an electrocution risk. Once power is shut off, the fire becomes a Class A hazard.

Class D extinguishers are for combustible metals such as magnesium, titanium, and sodium. Specialized dry powder agents are required because normal extinguishing agents are ineffective or can react dangerously with burning metals.

Class K extinguishers are designed for cooking oils and fats, particularly in commercial kitchens. Wet chemical agents saponify the oil, converting it into a non-flammable soap foam. Never use water or standard ABC extinguishers on a kitchen grease fire.