Fire is the process of chemical oxidation and combustion who's elements consist of fuel, oxygen, and heat. These
three elements are commonly referred to as the fire triangle. When all three elements of the fire triangle are
intact, and in the proper state and proportion, burning can take place, and when any of these elements are
removed, the burning will stop.
3.
Properties of Fire.
a. Ignition Temperature. Ignition temperature of a substance (solid, liquid, or gaseous) is the minimum
temperature to which the material exposed to air must be heated in to initiate or cause a self-sustained
combustion. Ignition temperature of the same material varies according to the percentage composition of the
vapor air mixture, shape, and size of space where the ignition occurs, rate and duration of heat, temperature of the
ignition source and oxygen concentration.
b. Vapors. Vapors in the process of combustion are the gaseous substance given off by the material that
is burning. In burning wood, heat causes the resinous substance in the wood to vaporize. The vapors combined
with the oxygen and the flame from the kindling ignites the combustible vapor-oxygen gas. The heat from the
fire heats the wood, which in turn creates more vapors and thus sustains the fire until the wood is consumed.
c. Vapor Explosive Range. When vapors from petroleum products are mixed with the proper amounts
of air (oxygen), they form explosive mixtures within a limited range. This range is usually called the explosive
range or explosive limits. (As used here, the word "explosion" means the instantaneous burning of a mixture of
flammable material and oxygen.) Gasoline vapors form explosive mixtures when mixed with air in a range from
about 1 to 8 percent by volume. This mixture within the explosive range ignites at once when it comes in contact
with a spark or flame.
(1) Upper explosive limits. A vapor-air mixture with more than 8 percent gasoline vapor is beyond
the upper limit and it does not ignite.
(2) Lower explosive limits. A vapor-air mixture with less than 1 percent gasoline vapor does not
ignite.
4.
Source of Ignition.
Source of ignition is any substance that can produce heat or a spark. Volatile petroleum fuels vaporize at normal
atmospheric temperatures, and the vapors burn readily when ignited. All fires connected with flammable products
result from the ignition of vapors. There is little danger in a closed container that holds a flammable product
unless it is exposed to heat. The hazard arises from tie ignition of vapors produced during transfer or use of
petroleum products and those resulting from spills or leaks. Fuel handles must remember that air and fuel are
present in all operations they perform. Heat is all that is needed to case a fire or an explosion. The best way to
prevent petroleum fires is to reduce vapor formation and control sources of ignition. Some of the most common
sources of ignition and control measures are as follows:
a. Smoking and Matches. Collect all smoking materials at the entrance checkpoint. Post "No Smoking
Within 50 Feet" signs where they can easily be seen.
b. Poor Housekeeping. Keep the area free of trash and similar combustibles that can be ignited by small
sources of heat.
c. Mechanical or Friction Sparks (impact between metals).
QM5200
2-2
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