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 TM 55-1905-223-SDC
to bear in the form of water fog. In the interim, Aqueous Film Forming Foam (AFFF) is most effective against
this type of fire. If power to the affected cables is completely deenergized, this type of fire is considered a
Class A fire.
b. Diesel fuel. Diesel fuel has a flash point of 140 F and an auto ignition (ignition without the
assistance of an external pilot source) temperature of 400 F. When ignited, it will produce a heavy black
smoke. The fire should be attacked using AFFF. If AFFF is not available, use dry chemical extinguishers.
Low-velocity water fog should be available when setting the reflash watch.
c. Hydraulic oil. Hydraulic oil has a flash point of about 400 F and an auto ignition temperature of
over 650 F. If hydraulic oil at 3,000 psi is atomized from a leak in a pipe, it will readily burn if exposed to an
ignition source. Laboratory tests indicate that the oil mist fire will continue to burn even if the ignition source is
removed when the oil is at the normal operating temperature of 110F to 130 F. A hydraulic oil fire can ignite
surrounding combustibles such as cable insulation and produce intense heat once its ignition temperature has
been reached. Such a fire will cause a pressure increase in a sealed compartment. Hydraulic oil spray/mist
fires should be attacked with dry chemical fire extinguishers. AFFF should be used against two-dimensional
fires. If the fire is an oil mist, the extinguisher should be aimed at the base of the fire until the flame is
extinguished. This will interrupt the fuel flow to the fire. If the fire cannot be extinguished by dry chemical
extinguishers, water should be brought to bear. Dry chemical extinguishers do not cool a fire; therefore,
reflash can be expected. Low velocity water fog should be available when setting the reflash watch.
d. Oil mist. If an oil leak mist accumulates before an ignition source is introduced, later ignition can
result in an explosion. It is important to secure and/or depressurize the source of the leak as soon as possible
and avoid actions that could cause an arc, sparking, or open flame before the mist is dispersed.
e. Vegetable oil. The vegetable oil used in cooking has a smoke point of 420 F, a flash point at 10F
to 20 F higher, and an autoignition temperature of about 600 F when fresh. Respective temperatures are
much lower when the oil has been used. If installed, the aqueous potassium carbonate system should be
used to extinguish a deep fat fryer fire. If not, AFFF or PKP extinguishers should be used, applying the AFFF
continuously or the chemical in short bursts of 3 seconds to extinguish flames. Repeat if oil reignites. The
range exhaust hood damper should be closed immediately. As soon as a fire hose with a low-velocity fog
applicator is charged, apply water fog simultaneously with a 3-second PKP extinguisher discharge if the fire is
still burning. If the oil reignites, repeat this procedure. Low-velocity fog should be maintained available for the
reflash watch.
f. Gasoline. Fires involving gasoline fuel can be extinguished only BY smothering. C02 provides only
temporary smothering and, the flammable vapors which continue to evolve from these fuels at ordinary
temperatures can easily be reignited causing the fire to begin all over again. Dry chemical agents provide a
more permanent smothering effect and should be utilized to avoid
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