Flammable liquids are always covered with a layer of
vapors. When mixed with air and contacted by an ignition
source, it is the vapor, not the liquid which burns. The
fuel vapor and oxygen provide two sides of the fire
triangle. A flammable liquid is usually more dangerous
when temperatures are high because more vapors are
Four terms are commonly used with flammable
The lowest temperature at which a liquid gives off
enough vapors to form a flammable mixture with air.
The lowest temperature at which the vapor-air mixture
will continue to burn after it is ignited. This is
generally a few degrees above the flash point.
The temperature at which a mixture of flammable vapor
and air will ignite without a spark or flame. This term
is also applied to the temperature of a hot surface
which will ignite flammable vapors. The temperature
varies with the type of surface.
FLAMMABLE OR EXPLOSIVE RANGE
The range between the smallest and largest amounts of
vapor in a given quantity of air which will explode or
burn when ignited. The amount is usually expressed in
percentages. For instance, carbon disulfide has an
explosive range of one to 50 percent. If air contains
more than one or less than 50 parts of carbon disulfide
vapor, the mixture can explode or burn.