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Flammability and Combustibility Gas Compounds

Heat Transfer Engineering

Flammability and Combustibility of Selected Gas and Compounds

Flammable describes any solid, liquid, vapor, or gas that will ignite easily and burn rapidly. A flammable liquid is defined by NFPA and USDOT as a liquid with a flash point below 100°F (38°C). Flammability is further defined with lower and upper limits:

LFL = lower flammability limit (volume % in air)
UFL = upper flammability limit (volume % in air)

The LFL is also known as the lower explosive limit (LEL). The UFL is also referred to as the upper explosive limit (UEL). There is no difference between the terms flammable and explosive as applied to the lower and upper limits of flammability.

A vapor-air mixture will only ignite and burn over the range of concentrations between LFL and UFL.

Reference

• From SFPE Handbook of Fire Protection Engineering, 4th ed., Society of Fire Protection Engineers, 2008.

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