Lel Uel r2y55

Reference Information

Lower and Upper Explosive Limits for Flammable Gases and Vapors (LEL/UEL) Before a fire or explosion can occur, three conditions must be met simultaneously. A fuel (ie. combustible gas) and oxygen (air) must exist in certain proportions, along with an ignition source, such as a spark or flame. The ratio of fuel and oxygen that is required varies with each combustible gas or vapor. The minimum concentration of a particular combustible gas or vapor necessary to its combustion in air is defined as the Lower Explosive Limit (LEL) for that gas. Below this level, the mixture is too “lean” to burn. The maximum concentration of a gas or vapor that will burn in air is defined as the Upper Explosive Limit (UEL). Above this level, the mixture is too “rich” to burn. The range between the LEL and UEL is known as the flammable range for that gas or vapor.

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The values shown in this table are valid only for the conditions under which they were determined (usually room temperature and atmospheric pressure using a 2 inch tube with spark ignition). The flammability range of most materials expands as temperature, pressure and container diameter increase. Sources: Data extracted from Gas Data Book, 7th edition, copyright 2001 by Matheson Gas Products, and from Bulletin 627, Flammability Characteristics of Combustible Gases and Vapors, copyright 1965 by U.S.Department of the Interior, Bureau of Mines.

All concentrations in percent by volume.

Gas Heptane Hexane Hydrogen Hydrogen Cyanide Hydrogen Sulfide Isobutane Isobutylene Isopropanol Methane Methanol Methylacetylene Methyl Bromide 3-Methyl-1-Butene Methyl Cellosolve Methyl Chloride Methyl Ethyl Ketone Methyl Mercaptan Methyl Vinyl Ether Monoethylamine Monomethylamine Nickel Carbonyl Pentane Picoline Propane Propylene Propylene Oxide Styrene Tetrafluoroethylene Tetrahydrofuran Toluene Trichloroethylene Trimethylamine Turpentine Vinyl Acetate Vinyl Bromide Vinyl Chloride Vinyl Fluoride Xylene

LEL 1.1 1.2 4.0 5.6 4.0 1.8 1.8 2.2 5.0 6.7 1.7 10.0 1.5 2.5 7.0 1.9 3.9 2.6 3.5 4.9 2.0 1.4 1.4 2.1 2.4 2.8 1.1 4.0 2.0 1.2 12.0 2.0 0.7 2.6 9.0 4.0 2.6 1.1

UEL 6.7 7.4 75.0 40.0 44.0 8.4 9.6 – 15.0 36.0 11.7 15.0 9.1 20.0 17.4 10.0 21.8 39.0 14.0 20.7 – 7.8 – 9.5 11.0 37.0 – 43.0 – 7.1 40.0 12.0 – – 14.0 22.0 21.7 6.6

Gas Acetone Acetylene Acrylonitrile Allene Ammonia Benzene 1,3-Butadiene Butane n-Butanol 1-Butene Cis-2-Butene Trans-2-Butene Butyl Acetate Carbon Monoxide Carbonyl Sulfide Chlorotrifluoroethylene Cumene Cyanogen Cyclohexane Cyclopropane Deuterium Diborane Dichlorosilane Diethylbenzene 1,1-Difluoro-1-Chloroethane 1,1-Difluoroethane 1,1-Difluoroethylene Dimethylamine Dimethyl Ether 2,2-Dimethylpropane Ethane Ethanol Ethyl Acetate Ethyl Benzene Ethyl Chloride Ethylene Ethylene Oxide Gasoline

LEL 2.6 2.5 3.0 1.5 15.0 1.3 2.0 1.8 1.7 1.6 1.7 1.7 1.4 12.5 12.0 8.4 0.9 6.6 1.3 2.4 4.9 0.8 4.1 0.8 9.0 5.1 5.5 2.8 3.4 1.4 3.0 3.3 2.2 1.0 3.8 2.7 3.6 1.2

UEL 13.0 100.0 17 11.5 28.0 7.9 12.0 8.4 12.0 10.0 9.7 9.7 8.0 74.0 29.0 38.7 6.5 32.0 7.8 10.4 75.0 88.0 98.8 – 14.8 17.1 21.3 14.4 27.0 7.5 12.4 19.0 11.0 6.7 15.4 36.0 100.0 7.1

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