What Does
Explosive (Flammable) Range Mean?
The explosive flammable range of a combustible gas or vapor is the range between the lower exposure limit (LEL) and the upper exposure limit (UEL) for that particular gas or vapor. This is the flammable range at which the gas will burn. Below this range, the substance is too lean to burn, and above it is too rich.
Safeopedia Explains Explosive (Flammable) Range
Three conditions must be met in order for an explosion to occur. There must be a fuel, oxygen must be present and their must he an ignition source. In the case of a combustible gas, the gas is the fuel, the atmosphere provides the oxygen and the ignition source is provided by a spark of flame.