Flammable (Explosive) Limits 2 : The lower and upper percentages by volume of concentration of gas in a gas-air mixture that will form an ignitable mixture. (See NFPA No. 325M). (RP500B)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}