Classes of fires: Class A fires are fires in ordinary combustible materials (e.g., paper, wood, cloth); Class B fires are those in combustible or flammable liquids, flammable gases, greases, and similar materials; Class C fires are those in electrical equipment; and Class D fires are those in combustible metals (e.g.. magnesium, sodium, potassium, etc.).
Class A - Fires in ordinary combustible materials such as wood, cloth, paper, etc. Class B - Fires in flammable liquids and gases such as oils and paints Class C - Fires involving energized electrical equipment where the electrical conductivity of the extinguishing medium is of importance. Class D - Fires involving combustible metals such as potassium or sodium