There are four classes of fires. All fire extinguishers are labeled, using standard symbols, for the classes of fires on which they can be used.
A red slash through any of the symbols tells you the extinguisher cannot be used on that class of fire. A missing symbol tells you only that the extinguisher has not been tested for a given class of fire, but may be used if an extinguisher labeled for that class of fire is not available.
Types of Fires:
CLASS A – Ordinary combustibles such as wood, cloth, and paper.
CLASS B – Flammable liquids such as gasoline, oil, and oil-based paint.
CLASS C – Energized electrical equipment, including wiring, fuse boxes, circuit breakers, machinery and appliances.
CLASS D – Combustible metals such as magnesium or sodium.