Lower Explosive Limit (Lel) 6 : The lowest concentration by volume of combustible gases in mixture with air that can be ignited at ambient conditions. (RP 14C)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}