Definition(s)
Lower Flammable Limit
The minimum concentration of a vapor in air (or other oxidant) below which propagation of flame does not occur on contact with an ignition source. The LFL is usually expressed as a volume percentage of the vapor in air. Sometimes called lower explosive limit (LEL). In popular terms, a mixture containing a percentage of flammable vapor below the LFL is too “lean” to burn.
Source:API Standards 2217A, Guidelines for Safe Work in Inert Confined Spaces in the Petroleum and Petrochemical Industries, Fourth Edition, July 2009. Global Standards
Lower Flammable Limit (Gas Properties)
Volume fraction of flammable gas or vapour in air below, which an explosive gas atmosphere does not form, expressed as a percentage (see IEC 60079-20)
NOTE This is also known as lower explosive limit (LEL).
Source: IEC 60079-29-1, Explosive atmospheres – Part 29-1: Gas detectors – Performance requirements of detectors for flammable gases. Global Standards
Lower Flammable Limit (LFL)
Lower flammable limit (LFL) means the concentration of a hydrocarbon gas in air below which there is insufficient hydrocarbon to support and propagate combustion.
Source: IMO MSC.1/Circ.1321, Guidelines for measures to prevent fires in engine-rooms and cargo pump-rooms, 11 June 2009, International Maritime Organization. Regulatory Guidance
Lower Flammable Limit (LFL)
Lower flammable limit (LFL) is the volume fraction of gas or vapour below which an explosive atmosphere does not form. Also referred to as lower explosive limit (LEL).
Source: IMO MSC.1/Circ.1370, Guidelines for the design, construction and testing of fixed hydrocarbon gas detection systems, 22 June 2010, International Maritime Organization. Regulatory Guidance