Water acts a cooling agent to extinguish the fire. Class B fires involve flammable liquids such as gasoline, oil, grease, tar, oil-based paint, lacquer, and flammable gas. Class B extinguishers use carbon dioxide gas, dry chemical or foam to cover the fire and exclude air. Class C fires involve energized electrical equipment including wiring, fuse boxes, circuit breakers, machinery, and appliances. Class C extinguishers require the use of non-conductive agents such as carbon dioxide or dry chemicals.
Carbon dioxide is the preferred agent, as it leaves no residue to be cleaned up.
Class D fires involve combustible metals such as magnesium and sodium. Care must be taken that no agent is used that might react with the metal. Extinguisher Sizes All extinguishers are rated as to the size of fire they are designed to handle. Installation and Maintenance Extinguishers should be installed in plain view above the reach of small children, near an escape route and away from stoves and heating appliances. Rechargeable models must be serviced after every use.