Definition(s)
Lower Explosive Limit (LEL)
“Lower Explosive Limit “ (LEL) means the lower limit of flammability of gas or vapor at ordinary ambient temperatures expressed by a percentage of gas or vapor in air by volume. This limit is assumed constant for temperatures up to 250°F (120°C) above this, it should be decreased by a factor of 0.7, because explosibility increases with higher temperatures.
Source: State of Wyoming Occupational Safety and Health Rules and Regulations for Oil and Gas Well Drilling, Revised January 8, 2013. Regulations