Flammable hazards Solvents, chemicals, and other sources of flammable vapors and gases are present in many manufacturing, manufacturing and conversion processes and serve as fuel during combustion or explosion. In most industrial processes, there is enough oxygen to support combustion. But even in inert or treated processes, the sudden introduction of air can mix with process vapor to create a flammable mixture. Flammability measurement For each flammable substance, there is a concentration level in the air, usually expressed as a percentage by volume, known as the Lower Flammability Limit, LFL or the Lower Explosive Limit, LEL. Below the LFL, the mixture of fuel and air is too thin to support combustion. For example, a mixture of 1.1% Hexane in air equals 100% of its LFL — rich enough to burn
