stand ready at all times to shift combustibles to safe
fire can be reached faster if you quickly secure all
ventilation systems to the space. In general, a large
areas. Take whatever measures possible to keep
enough volume of C02 must be used to reduce the
additional fuel away from the fire. In particular,
oxygen content to 15 percent or less.
immediately close supply valves in fuel oil, lube oil, and
JP-5 lines.
REDUCING THE RATE OF COMBUSTION
REMOVING HEAT
Dry chemical fire extinguishing agents and Halon
1301 do not extinguish fires by cooling or smothering.
The fire will go out if you can remove enough heat
Instead, they are believed to interrupt the chemical
by cooling the fuel to below temperature at which it
reaction of the fuel and oxygen. This action reduces the
will support combustion. Heat may be transferred in
rate of combustion, and the fire is extinguished quickly.
three ways as follows:
Speed is very important in fire fighting. If you allow
1.
By radiation
a fire to burn without confining or extinguishing it, the
2.
By conduction
fire can spread rapidly. A small fire in a trash can may
spread to other combustibles and become a large fire
3.
By convection
that could affect several compartments or even the
In the process known as radiation, heat is radiated
whole ship. The cost of damage that may have originally
through the air in all directions. Radiated heat is what
been a few dollars could end up costing millions of
causes you to feel hot when you stand near an open fire.
dollars. Therefore, the ship's fire party must get to the
In conduction, heat is transferred through a substance
scene with their equipment and start fighting the fire as
or from one substance to another by direct contact from
soon as possible. Any delay that allows the fire to spread
molecule to molecule. Therefore, a thick steel
will make it more difficult to extinguish the fire with the
bulkhead with a fire on one side can conduct heat from
personnel and equipment available.
the fire and transfer the heat to the adjoining
compartments. In convection, the air and gases rising
REVIEW QUESTIONS
from a fire are heated. These gases can then transfer the
heat to other combustible materials that are within
Q11.
Which of the following processes is NOT a
reach. Heat transferred by convection is a particular
method of transferring heat?
danger in ventilation systems. These systems may
1.
carry the heated gases from the fire to another location
2.
Conduction
several compartments away. If there are combustibles
with a low flash point within a compartment served by
3.
Convection
the same ventilation system, a new fire may start.
4.
Glaciation
To eliminate the heat side of the fire triangle, cool
Q12.
Heat, fuel, and oxygen are the three
the fire by applying something that will absorb the
components of the fire triangle.
heat. Although several agents serve this purpose, water
is the most commonly used cooling agent. Water may
1.
True
be applied in the form of a solid stream, as a fog, or
2.
False
used together with aqueous film-forming foam
(AFFF).
CONTROLLING OXYGEN
EXTINGUISHING AGENTS
Oxygen is the third component of the fire triangle.
Learning Objective: Recall the different extinguishing
Oxygen is difficult to control because you obviously
agents used to extinguish fires.
cannot remove the oxygen from the atmosphere that
The extinguishing agents commonly used by Navy
normally surrounds a fire. However, oxygen can be
fire fighters include the following:
diluted or displaced by other substances that are
noncombustible. For example, if a fire occurs in a closed
Water
space, it can be extinguished by diluting the air with
carbon dioxide (C02) gas. This dilution must proceed to
Aqueous film-forming foam (AFFF)
a certain point before the flames are extinguished. The
Purple-K-Powder (PKP)
point at which the dilution is enough to extinguish the
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