High Quality Content by WIKIPEDIA articles! Lower flammability limit (LFL), usually expressed in volume per cent, is the lower end of the concentration range of a flammable solvent at a given temperature and pressure for which air/vapor mixtures can ignite. The flammability range is delineated by the upper and lower flammability limit. Outside this range of air/vapor mixtures, the mixture will not ignite (unless heated). The LFL decreases with increasing temperature; thus, a mixture that is below its LFL at a given temperature may ignite if heated sufficiently. The LFL is typically close to the saturated vapor concentration at the flash point, however, due to differences in technique between measuring LFL and the various flash points (open/closed cup as well as different apparatus) some spread in the data usually exists.