LEL stands for Lower Explosive Limit in gas detection. The Lower Explosive Limit is the lowest concentration of a gas or vapour that can ignite or explode in the presence of an ignition source. The LEL is expressed as a percentage of the gas or vapour in air. For example, the LEL of methane is 5%, which means that if the concentration of methane in the air is below 5%, it is not flammable, but if it exceeds 5%, it can ignite if there is a source of ignition such as a spark or flame.
LEL is an important parameter to monitor in industrial settings where flammable gases or vapours may be present, such as in petrochemical plants, refineries, and natural gas processing facilities. Gas detectors that measure LEL are designed to provide an early warning of potentially hazardous conditions, allowing workers to take appropriate safety measures, such as shutting down equipment or evacuating the area.