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

Flash point

The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source...

, 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.

See also

• Flammability limit
  Flammability limit
  Flammability limits, also called flammable limits, give the proportion of combustible gases in a mixture, between which limits this mixture is flammable. Gas mixtures consisting of combustible, oxidizing, and inert gases are only flammable under certain conditions. The lower flammable limit ...
  
  
• Flammability
  Flammability
  Flammability is defined as how easily something will burn or ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. Internationally, a variety of test protocols exist to quantify flammability...
  
  
• Flash point
  Flash point
  The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air. Measuring a flash point requires an ignition source...
  
  
• Minimum Ignition Energy
  Minimum Ignition Energy
  Minimum ignition energy is the minimum amount of energy required to ignite a combustible vapor, gas or dust cloud, for example due to an electrostatic discharge. MIE is measured in joules ....
  
  
• Petroleum
  Petroleum
  Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
  
  
• Upper flammable limit