%LEL

The lower explosive limit (LEL) or lower flammable limit (LFL) of a combustible gas is the smallest amount of the gas that supports a self-propagating flame when mixed with air (or oxygen) and ignited. In gas-detection systems, the amount of gas present is specified as a percentage (%) LEL. Zero percent (0%) LEL denotes a combustible gas-free atmosphere. One hundred percent (100%) lower explosive limit denotes an atmosphere in which gas is at its lower flammable limit. The relationship between percent LEL and percent by volume differs from gas to gas.