(Fire Pr) A hand-portable or wheeled device that can be used to extinguish small or incipient fires. Typically a container filled with any of a variety of fire extinguishing agents and means for expelling them. Note: Extinguishers are usually labeled with instructions for proper use. Some fire extinguishers are effective only on one class of fire; others are suitable on two or three classes. None are suitable for all four classes of fire. Class A. : Afire extinguisher for use on fires involving ordinary combustiblematerials such as wood, cloth, paper, rubber, and many plastics. Class B. For fires involving flam or combustible liquids, flammable gases, greases, and similar materials. Class C: For fires in-volving energized electrical equipment where safety to the operator requires the use of electrically nonconductive extinguishing agents. (When electrical equipment is deenergized, Class A or B extinguishers may be effective. Class D: For fires involving certain combustible metals such as magnesium, titanium, zirconium, sodium, and potassium. CO2: A fire extinguisher that discharges carbon dioxide gas; suitable for Class B and Class C fires. dry powder: A fire extinguisher that discharges a fine dry powder, usually sodium bicarbonate, potassium bicarbonate, or ammonium phosphate, by the pressure of a compressed gas stored in the same container as the powder; generally suitable for Class B and Class C fires. sodaacid: A fire extinguisher that discharges water by the pressure of carbon dioxide gas that is produced by the mixing of acid and soda when the extinguisher is actuated. Caution: the water may contain unreacted acid or soda