chemical reaction by which oxygen combines
chemically with the burning material.
Such things as rags or paper soaked with oil or with
paints or solvents are particularly subject to
spontaneous combustion if they are stowed in confined
spaces where the heat caused by oxidation cannot be
dissipated rapidly enough.
A fire involving combustible fuel or other material
must have an ignition source, and the material must be
hot enough to burn. The lowest temperature at which a
flammable material gives off vapors that will burn when
a flame or spark is applied is called the flash point. The
fire point, which is usually a few degrees higher than the
flash point, is the temperature at which the fuel will
continue to burn after it has been ignited. The ignition or
self-ignition point is the lowest temperature to which a
material must be heated to give off vapors that will burn
without the aid of a spark or flame. In other words, the
ignition point is the temperature at which spontaneous
combustion occurs. The ignition point is usually at a
much higher temperature than the fire point.
METHODS OF HEAT TRANSFER
Heat from a fire is transferred by one or more of the
following methods:
1. Conduction
2. Convection
3. Radiation
Conduction
Conduction is the transfer of heat through a body or
from one body to another by direct physical contact. For
example, on a hot stove, heat is conducted through the
pot to its contents. Wood is ordinarily a poor conductor
of heat, but metals are good conductors. Since most
ships are constructed of metal, heat transfer by
conduction is a potential hazard. Fire can move from
one fire zone to another, one deck to another, and one
compartment to another by heat conduction.
Often, the skillful application of water, using fog
patterns to rapidly coat and recoat surfaces with a film of
water, will slow or halt the transmission of heat by
conduction. Fog patterns coat surfaces more efficiently
12-20
Student Notes:
Figure 12-8.—Tetrahedron and fire triangle.
