Flammability Ranges

If the vapors of a flammable liquid mix with air while in the presence of an ignition source, an explosion can occur. There is a minimum quantity of vapors or air that are required for an explosion to take place. This amount is called the lower flammable limit (LFL). There is also a maximum proportion of vapor to air in which an explosion does not occur. This is called the upper flammable limit (UFL). These numbers are typically expressed as a percentage of volume of vapor in the air.

The range of numbers in between the LFL and UFL is known as the flammability range.

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