than solid streams, reducing run off and the effect on
ship stability.
Convection
Convection is the transfer of heat through the
motion of circulating gases or liquids. Heat is
transferred by convection through the motion of smoke,
hot air, and heated gases produced by a fire.
When heat is confined (as within a ship), convected
heat moves in predictable patterns. The fire produces
lighter than air gases that rise toward high parts of the
ship. Heated air, which is lighter than cooler air, also
rises. As these heated combustion products rise, cool air
takes their place; the cool air is heated, in turn, and then
rises to the highest point it can reach.
Hot smoke originating at a fire on a low deck will
travel horizontally along passageways, and then upward
by way of ladder and hatch openings, heating
flammable materials in its path. To prevent fire spread,
release the heat, smoke, and gases to the atmosphere.
However, the structural design of a ship makes it
difficult to rapidly cut openings through decks,
bulkheads, or the ship’s hull for ventilation. It is
imperative that the fire be confined to the smallest
possible area. Doors and hatchways should be kept
closed when they are not in use. If a fire is discovered,
attempts should be made to close off all openings to the
fire area until firefighting personnel and equipment can
be brought into position to fight the fire.
Radiation
Heat radiation is the transfer of heat from a source
across an intervening space; no material substance is
involved. The heat travels outward from the fire in the
same manner as light; that is, in straight lines. When it
contacts a body, it’s absorbed, reflected, or transmitted.
Absorbed heat increases the temperature of the
absorbing body. For example, radiant heat that is
absorbed by an overhead will increase the temperature
of that overhead, perhaps enough to ignite its paint.
Heat radiates in all directions unless it’s blocked.
Radiant heat extends fire by heating combustible
substances in its path, causing them to produce vapors,
then igniting the vapor.
Within a ship, radiant heat raises the temperature of
combustible materials near the fire and, depending on
the ship’s design, at quite some distance from the fire.
Ship fires can spread as a result of radiating bulkheads
and decks. Intense radiated heat can make an approach
to the fire extremely difficult. For this reason, protective
clothing should be worn by firefighters.
REVIEW 6 QUESTIONS
Q1. Fire prevention is the responsibility of—
Q2. List the three components that make up a fire.
a.
b.
c.
Q3. What process is involved in most cases of
spontaneous combustion?
Q4. List the three methods of heat transfer.
a.
b.
c.
CLASSES OF FIRE
Learning Objective: When you finish this chapter, you
will be able to—
Recognize the four classifications of fire and
identify the means used to extinguish them.
Fires are divided into four classifications, each
indicating the type of material burning. By knowing the
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Student Notes:
