The minimum concentration of vapor in air or oxygen below which propagation of a flame does not occur on contact with a source of ignition, and the maximum proportion of vapor or gas in air above which propagation of a flame does not occur; usually expressed in terms of percentage by volume of gas or vapor in air. A change in temperature or pressure may vary the flammable limits of a gas.
The percent by volume limits (i.e., upper and lower flammable limits) of flame propagation does not occur on contact with a source of ignition. See flammable range.
The range of concentrations in air of flammable vapors of a substance between which the vapors will ignite and continue to burn; possibly resulting in an explosion. The lower limit is the Lower Flammable (or explosive) Limit, LFL, and the upper limit is the Upper Flammable (or explosive) Limit, UFL. Below the LFL, there is not enough vapor to support combustion. Above the UFL there is too much vapor. The mixture is too much to burn. NOTE: The MSDS uses Explosive Limit, but the preferred term is Flammable Limit. The terms are synonymous.
Flammables have a minimum concentration below which propagation of flame does not occur on contact with a source of ignition. This is known as the lower flammable explosive limit (LEL). There is also a maximum concentration of vapor or gas in air above which propagation of flame does not occur. This is known as the upper flammable explosive limit (UEL). These units are expressed in percent of gas or vapor in air by volume.
The concentration limits between which a flammable gas or vapor may ignite. Concentrations below the lower flammable limit (LFL) are too lean to burn, while those above the upper flammable limit (UFL) are too rich.
For gases or vapors which form flammable mixtures with air or oxygen, there is a minimum concentration of vapor in air or oxygen below which propagation of flame does not occur on contact with a source of ignition. There is also a maximum proportion of vapor or gas in air above which propagation of flame does not occur. These boundary-line mixtures of vapor or gas with air, which if ignited will just propagate flame, are known as the lower and upper flammable limits (LFL and UFL) or the lower and upper explosive limits (LEL and UEL), and are expressed in terms of percentage by volume of gas or vapor in air. LEL and LFL are different terms for the same concept. In popular terms, a mixture below the LFL/LEL is too "lean" to burn or explode and a mixture above the UFL/UEL is too "rich" to burn or explode.
The upper and lower concentration limits for a flammable gas, above and below which flame propagation does not occur upon contact with a source of ignition. Flammable limits are calculated at ambient temperature and pressure in the air.
The lowest and highest concentrations of vapor or gas in the air that will ignite when exposed to a spark of flame. There are two types: the Lower Flammable Limit (LFL, or LEL) and the Upper Flammable Limits (UFL, or UEL). Products with wide flammable limits (such as ethyl ether, 1.9-36) may ignite either near or far away from an ignition source, while products with narrow flammable limits may ignite only near the ignition source. When considering the explosion hazards, the LFL is the most important. The lower the LFL, the less of a substance needed in the air before it can ignite.
