Fire Extinguishers Classification
Types of Fires
Fire extinguishers are divided into five categories based on different types of fires. Each fire extinguisher has a numerical rating that also serves as a guide for the amount of fire the extinguisher can extinguish. The higher the number, the more power the extinguisher has to fight flames. The following is a quick guide to help choose the right type of extinguisher.
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 are suitable for use on electrically energized fires. This class of fire extinguishers does not have a numerical rating. The presence of the letter "C" indicates that the extinguishing agent is non-conductive.
Class D Extinguishers are designed for use on flammable metals and are often specific for the type of metal in question. Class D hazards are very dangerous. They burn hot (2500 F for magnesium, even higher for other metals). Most react violently with water, Halons, Halon substitutes and CO2. They emit toxic vapors (lithium fires produce huge amounts of dense smoke; the best
extinguisher to use on lithium fires is the extinguisher with a copper agent). Proper extinguishing technique may require 8 - 15 lbs. or more of extinguishing agent per pound of burning material.
Class K fires are kitchen fires. This class was added to the NFPA portable extinguishers Standard 10 in 1998. Since July 1, 1998, all new extinguishers installed in restaurant kitchens must be K class rated.
Note: Many extinguishers available today can be used on different types of fires and will be labeled with more than one designator, e.g. A-B, B-C, or A-B-C. If you have a multi-purpose extinguisher make sure that it is properly labeled.