Lower Flammability Limit. The lower flammability limit (LFL) is defined by the ASTM Standard E 681-85 as "the minimum concentration of a combustible substance that is capable of propagating a flame through a homogeneous mixture of the combustible and gaseous oxidizer under the specified conditions of test" /AST85/. The conditions of test usually reported for refrigerants are in dry air in ambient temperature and pressure.

Lower Flammable Limit - The lower limit of flammability of a gas or vapor at ordinary ambient temperatures expressed in percent of the gas or vapor air by volume.  This limit is assumed constant for temperatures up to 250° F(120° C) and is normally listed on a product's material safety data sheet.

Lower flammability limit. The minimum concentration of a combustible gas in air which will ignite if a source of ignition is present. Used interchangeably with the term "lower explosive limit" (LEL).

See LOWER EXPLOSIVE LIMIT.

Lower Flammability Limit, the minimum concentration in air at which flame propagation occurs