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
Extinguish flammable liquids, greases
or gases by removing the oxygen, preventing the vapors from reaching the
ignition source or inhibiting the chemical chain reaction. Foam, carbon
dioxide, ordinary (BC-rated) dry chemical, multi-purpose dry chemical,
and halon extinguishers may be used to fight Class B fires.
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.
* Even though halon is widely used, EPA legislation is phasing it out of use in favor of agents less harmful to the environment.
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
NOTE: 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 on campus.