Not all fires are the same. If you use the wrong type of fire extinguisher on the wrong class of fire, you can, in fact, make matters worse.
To assist people quickly identify the right type of fire extinguisher, pictographs are used to represent different classes of fire. There are six different classes represented by the letters A, B, C, D, E and F.
These pictographs can be found on all modern fire extinguishers and indicate which classes of fires the extinguisher will work for, or should not be used for.
Fires are normally classified according to the fuel involved, however, any fire that involves energised electrical equipment is always classified as a class (E) until the electrical circuit is disconnected. It is then reclassed according to the type of material that is burning.
Class A Extinguishers will put out fires in ordinary combustibles, such as wood and paper. The numerical rating for this class of fire extinguisher refers to the amount of water the fire extinguisher holds and the amount of fire it will extinguish.
Class B Extinguishers should be used on fires involving flammable liquids, such as grease, gasoline, oil, etc. The numerical rating for this class of fire extinguisher states the approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish.
Class C Extinguishers should be used on fires involving flammable liquids, such as grease, gasoline, oil, etc. The numerical rating for this class of fire extinguisher states the approximate number of square feet of a flammable liquid fire that a non-expert person can expect to extinguish.
Class D Extinguishers are designed for use on flammable metals and are often specific for the type of metal in question. There is no picture designator for Class D extinguishers. These extinguishers generally have no rating nor are they given a multi-purpose rating for use on other types of fires.
Class E Extinguishers are suitable for use on electrically energised fires. This class of fire extinguishers does not have a numerical rating. The presence of the letter indicates that the extinguishing agent is non-conductive.
Class F Extinguishers are suitable for cooking oils and fats, such as the cooking oils and fats usually found in industrial kitchens etc.
Portable fire extinguishers are generally inspected checked twice per year in accordance with Australian Standard AS1851.