There are four classes of fires:

Class A: Ordinary solid combustibles such as paper, wood, cloth and some plastics.
Class B: Flammable liquids such as alcohol, ether, oil, gasoline and grease, which are best extinguished by smothering.
Class C: Electrical equipment, appliances and wiring in which the use or a nonconductive extinguishing agent prevents injury from electrical shock. Don’t use water.
Class D: Certain flammable metallic substances such as sodium and potassium. These materials are normally not found in the Medical Center.