Tutorial Guide to Gas Detection - Presentations

The Lower Explosive Limit (LEL) or Lower Flammability Limit (LFL) defines the lowest concentration of a combustible in air that allows the explosion. There could be a high explosion risk even with very small gas concentrations: in fact a great part of flammable gases and vapors have the LEL figure below 5% of volume. The Upper Explosive Limit (UEL) defines the maximum concentration of fuel in air that may causes explosion. Concentrations of the combustible above the UEL cannot generate explosion because of the insufficient concentration of the combustion supporter (typically Oxygen).