Lower Flammability Limit (LFL)

What Does Lower Flammability Limit (LFL) Mean?

Lower flammability limit (LFL) refers to the lower limit of the gaseous or vaporized fuel, combustible material or dust’s concentration in the air, at a fixed temperature and pressure, which can lead to flame propagation, detonation or an explosion. Fuel or combustible volumetric concentrations below LFL are non-flammable and are considered safe.

Safeopedia Explains Lower Flammability Limit (LFL)

LFL is expressed in terms of % of volume, at 25 °C and sea level atmospheric pressure. It decreases with the temperature increase. Therefore, any combustible mixture that is at a lower % than the LFL may ignite if heated adequately.

Comparing to the flash point of liquid, LFL is near the saturated vapor concentration. However, this relation is not constant. LFL is sometimes referred as lower explosive limit (LEL) by some safety professionals.