UFC 3-460-03
21 JANUARY 2003
8.4. Preventing Petroleum Fires.
8.4.1. General. The absence of any one of the conditions listed in paragraph 8.4.1, as represented by
the missing leg of the fire triangle, prevents a fire. It is not practical to eliminate air completely or to
control air-vapor proportions where gasoline is handled and dispensed. Temperatures cannot be
controlled to the point where vapors are not possible; therefore, to eliminate all sources of ignition, it
is essential to prevent fires. NOTE: Liquid oxygen coming in contact with fuel reacts violently to
produce spontaneous combustion. It is mandatory that these materials be kept isolated from each
other. Three simultaneous conditions are necessary to create petroleum fires:
8.4.1.1. Petroleum must be in the form of vapor.
8.4.1.2. Air-vapor mixture must be present in the correct proportion to support combustion or
explosion.
8.4.1.3. The combustible mixture of air and petroleum vapor must be raised to its ignition
temperature or subjected to a source of ignition.
8.4.2. Sources of Fire and Explosion.
8.4.2.1. Vapors above the explosive limit are not combustible if the tank is not opened; however,
after the tank has been opened vapors escaping to the atmosphere are quickly diluted to within the
explosive limit, and, if ignited, will cause fire at manholes and other tank outlets. Eventually the
vapor concentration in the tank is diluted, creating a fire and explosion hazard within the tank.
8.4.2.2. Extra precautions must be taken when venting a tank to be sure all sources of ignition are
eliminated. Petroleum vapors are heavier than air and will travel several hundred feet before they
dissipate into the atmosphere. Any source of ignition may ignite these vapors and cause a
flashback, resulting in fatalities of personnel caught in the flashback and loss of the property
issuing such vapors.
8.4.2.3. Sludge and other saturated material (e.g., sediment, hollow roof supports, sidewall scale,
oil-soaked wooden structures) continuously release petroleum vapors. These vapors can
accumulate to above the explosive limit in an enclosed area. A tank should not be declared safe
until all such materials have been removed.
8.4.2.4. Primary contributors to vapor ignition are static or stray electrical currents and personal
negligence. The human factor can be reduced by education and taking strict disciplinary action
against safety regulation violators.
8.4.3. Preventive Measures. Preventing petroleum fires can best be done by reducing or controlling
the open presence of petroleum products and vapors, and by eliminating sources of ignition, as
follows:
8.4.3.1. Provide proper ventilation for pumphouses, pits, and other enclosed spaces where
petroleum vapors may accumulate.
8.4.3.2. Take all precautions to prevent petroleum product leaks or spills.
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