The proper way to use a fire extinguisher is by using the P.A.S.S. method.
P- Pull the pin.
A- Aim the extinguisher nozzle at the base of the flames.
S- Squeeze the trigger while holding the extinguisher upright.
S- Sweep the extinguisher from side to side, covering the area of the fire with the extinguishing agent.
Identify the Proper Fire Extinguisher
All ratings are shows on the extinguisher faceplate. Some extinguishers are marked with multiple ratings such as AB, BC and ABC. These extinguishers are capable of putting out more than one class of fire.
Multipurpose (ABC-rated) chemical extinguishers leave a residue that can harm sensitive equipment, such as computers and other electronic equipment. Because of this, carbon dioxide or halon extinguishers are preferred in these instances because they leave very little residue.
ABC dry powder residue is mildly corrosive to many metals. For example, residue left over from the use of an ABC dry powder extinguisher in the same room with a piano can seriously corrode piano wires.
Carbon dioxide or halon extinguishers are provided for most labs and computer areas.
Class A and B extinguishers carry a numerical rating that indicates how large a fire an experienced person can safely put out with that extinguisher. Extinguish flammable liquids, greases or gases by removing the oxygen, preventing the vapors from reaching the ignition source or inhibiting the chemical chain reaction.
Class A and B extinguishers carry a numerical rating that indicates how large a fire an experienced person can safely put out with that extinguisher. Extinguish ordinary combustibles by cooling the material below its ignition temperature and soaking the fibers to prevent re-ignition.
Use pressurized water, foam or multi-purpose (ABC-rated) dry chemical extinguishers. DO NOT USE carbon dioxide or ordinary (BC-rated) dry chemical extinguishers on Class A fires.
Foam, carbon dioxide, ordinary (BC-rated) dry chemical, multi-purpose dry chemical, and halon extinguishers may be used to fight Class B fires.
Class C extinguishers have only a letter rating to indicate that the extinguishing agent will not conduct electrical current. Class C extinguishers must also carry a Class A or B rating. Extinguish energized electrical equipment by using an extinguishing agent that is not capable of conducting electrical currents.
Carbon dioxide, ordinary (BC-rated) dry chemical, multi-purpose dry chemical and halon* fire extinguishers may be used to fight Class C fires. DO NOT USE water extinguishers on energized electrical equipment.
Class D extinguishers carry only a letter rating indicating their effectiveness on certain amounts of specific metals. Extinguish combustible metals such as magnesium, titanium, potassium and sodium with dry powder extinguishing agents specially designated for the material involved. In most cases, they absorb the heat from the material, cooling it below its ignition temperature.