1. 3. DRY CHEMICALS TYPE FIRE EXTINGUISHER
● This type is suitable for tracking gas fire, fires is electrical equipment. The chemical
powder employed is usually sodium based and when applied to a fire undergoes
chemical reaction.
● Chemical dry powders containing mixtures of sodium, potassium and barium
compounds have been found useful in extinguishing fires in metals such as sodium
and magnesium.
● The chemical powder is contained in the main shell and CO2 gas is held under high
pressure in a sealed cartridge. When the extinguisher is operated, the cartridge is
broken allowing CO2 gas to escape to the main shell and push out the powder in the
form of fog.
2. OPERATION
Carry the extinguisher to the place of fire
and keep it upright. Remove the safety
clip and strike the knob located in the cap
to activate the piercing mechanism which
in turn breaks the sealing disc of the
cartridge. Direct the stream of escaping
powder at the base of the flame. For
effective result stand about 5 to 8 feet
away and direct the stream near the seat of
the fire, progress forward, moving the
nozzle rapidly with a side to side
sweeping motion. When using on outdoor
fires always operate extinguisher from the
upwind side for the fire.
3. 4. CARBON-DI-OXIDE TYPE FIRE EXTINGUISHER.
● CO2 is effective as an extinguishing agent primarily because it reduces the oxygen
content of air to a point where combustion cannot continue.
● CO2 is non-combustible and does not react with most substances. Being a gas it can
penetrate and spread to all areas affected by fires.
● These fire extinguishers are used for putting out fires in petroleum products, gaseous
substances under pressure and also in sophisticated electrical and electronic
apparatus.
Carbon-di-oxide extinguishers are not to be used in
● Fires involving chemicals that contain their own oxygen supply.
● Fires involving reactive metals such as sodium, potassium and magnesium.
4. OPERATION
Carry the extinguisher to the place of fire.
Remove the safety pin and operate the
discharge device or unscrew the valve
depending on the design. Direct the jet at
the base of fire, starting at one edge and
sweeping across the surface of the burning
material. When used in open air, the
operator should stand on the up-wind side
of the fire and should apply the gas in a
downwind direction as close as possible to
the fire. On fires in electrical equipment
first switch off the current then direct the
jet or horn straight at the fire.
5. 5. HALON TYPE FIRE EXTINGUISHER
● Halon is the most effective extinguishing agent than any other extinguishing agent. It
is ideal for intense and rapid flammable fires.
● Halon is non-conductive and leaves no traces, when applied. So it is also suitable for
electrical fires, computer rooms etc.
● Halon extinguishing the fire by interrupting the chain reactions which takes place at
the flame zone for continuance of fire.
● Halon is twice as effective as carbon-di-oxide on a weight basis and five times as
effective as carbon-di-oxide on volume basis.
6. OPERATION
Carry the extinguisher to the place of fire,
remove the safety pin and operate the discharge
device. When operated it is discharged as a
semiliquid jet at a high velocity and evaporate
rapidly to cover a fire in a blanket of mist. The
halogenated extinguishing agents are known as
Halons. Halogenated extinguishing agents are
hydrogen in which one or more hydrogen atoms
have been replaced by atoms from the halogen
series i.e., fluorine, chlorine, bromine and
iodine. There are many halogenated but only
two are most effective and less toxic. They are
Halons 1301nand Halon 1211.
