Fires are classified differently by how they are ignited.
A – Ordinary combustibles or fibrous material, such as wood paper, cloth, rubber and some plastics
B – Flammable or combustible liquids such as gasoline, kerosene, paint, paint thinners and propane
C – Energized electrical equipment, such as appliances, switches, panel boxes and power tools
D – Certain combustible metals, such as magnesium, titanium, potassium and sodium. These metals burn at high temperatures and give off sufficient oxygen to support combustion. They may react violently with water or other chemicals, and must be handled with care
K – Cooking oils, trans-fats or fats in cooking appliances
Fire extinguishers are rated using these letters to determine which chemicals are most effective on ceasing the fire.