Combustibles
Flammable and combustible chemicals are those that evaporate fast enough to generate sufficient vapor to ignite in the presence of an ignition source. The temperature at which this can occur is the chemical’s flash point.
In addition, flammable and combustible chemicals are those that can react with oxidizers, to cause a fire or explosion. Combustible materials will generate sufficient vapors at or above 100°F (37.8°C). Flammable chemicals will generate sufficient vapors at temperatures below 100°F (37.8°C).
Material Safety Data Sheets may also list a chemical’s auto-ignition temperature, which is the lowest temperature at which there is enough heat energy to ignite vapors spontaneously.
Other important characteristics of flammable and combustible chemicals are their explosive limits. The Lower Explosive Limit (LEL or lower flammable limit) is the lowest concentration of the substance in air that will produce a flash of fire when an ignition source is present. The Upper Explosive Limit (UEL or upper flammable limit) is the highest concentration of the substance in air that will produce a flash of fire when an ignition source is present.
At higher concentrations than the UEL, the mixture is too rich to burn. At concentrations lower than the LEL, the mixture is too lean to burn. Note that for flammable chemicals that are also toxic, concentrations at which the flammability is a hazard are usually well above the toxicity hazard concentrations.
Table of LEL’s/UEL’s
| Gas | LEL (% by volume) | UEL (% by volume) |
|---|---|---|
| Acetone | 2.6 | 12.8 |
| Acetylene | 2.5 | 100 |
| Acrolein | 2.8 | 31 |
| Acrylonitrile | 3 | 17 |
| Allene (propadiene) | 1.5 | 11.5 |
| Ammonia | 15 | 28 |
| Benzene | 1.3 | 7.9 |
| 1,3-Butadiene | 2 | 12 |
| Butane | 1.6 | 8.4 |
| n-Butanol | 1.4 | 11.2 |
| 1-Butene | 1.6 | 10 |
| Cis-2-Butene | 1.7 | 9.7 |
| Trans-2-Butene | 1.7 | 9.7 |
| Butyl Acetate | 1.7 | 7.6 |
| Carbon Disulfide | 1.3 | 50 |
| Carbon Monoxide | 12.5 | 74 |
| Carbonyl Sulfide | 12 | 29 |
| Chlorotrifluoroethylene | 8.4 | 38.7 |
| Cumene | 0.9 | 6.5 |
| Cyanogen | 6.6 | 32 |
| Cyclohexane | 1.3 | 7.8 |
| Cyclopropane | 2.4 | 10.4 |
| Decaborane | 0.2 | --- |
| Deuterium | 4.9 | 75 |
| Diborane | 0.8 | 88 |
| Dichlorosilane | 4.1 | 98.8 |
| Diethylbenzene | 0.8 | --- |
| Diethyl Ether | 1.9 | 36 |
| 1,1-Difluoro-1-Chloroethane | 9 | 14.8 |
| 1,1-Difluoroethane | 5.1 | 17.1 |
| 1,1-Difluoroethylene | 5.5 | 21.3 |
| Dimethylamine | 2.8 | 14.4 |
| Dimethyl Ether | 3.4 | 27 |
| 2,2-Dimethylpropane | 1.4 | 7.5 |
| Dimethyl Sulfide | 2.2 | 20 |
| Ethane | 3 | 12.4 |
| Ethanol | 3.3 | 19 |
| Ethyl Acetate | 2.2 | 11 |
| Ethyl Amine | 3.5 | 14 |
| Ethyl Benzene | 0.8 | 6.7 |
| Ethyl Chloride | 3.8 | 15.4 |
| Ethylene | 2.7 | 36 |
| Ethylene Oxide | 3 | 100 |
| Gasoline | 1.2 | 7.1 |
| Heptane | 1.1 | 6.7 |
| Hexane | 1.2 | 7.4 |
| Hydrazine | 2.9 | 98 |
| Hydrogen | 4 | 75 |
| Hydrogen Cyanide | 5.6 | 40 |
| Hydrogen Sulfide | 4 | 44 |
| Isobutane | 1.8 | 8.4 |
| Isobutylene | 1.8 | 9.6 |
| Isopropanol | 2.2 | 12.7 |
| Methane | 5 | 15 |
| Methanol | 6.7 | 36 |
| Methylacetylene | 1.7 | 11.7 |
| Methyl Bromide | 10 | 15 |
| 3-Methyl-1-Butene | 1.5 | 9.1 |
| Methyl Butyl Ketone | 1.2 | 8 |
| Methyl Cellosolve | 1.8 | 14 |
| Methyl Chloride | 8.1 | 17.4 |
| Methyl Ethyl Ketone | 1.4 | 11.4 |
| Methyl Mercaptan | 3.9 | 21.8 |
| Methyl Vinyl Ether | 2.6 | 39 |
| Monoethylamine | 3.5 | 14 |
| Monomethylamine | 4.9 | 20.7 |
| Monomethylhydrazine | 2.5 | 92 |
| Nickel Carbonyl | 2 | --- |
| Pentane | 1.4 | 7.8 |
| Picoline | 1.4 | --- |
| Propane | 2.1 | 9.5 |
| Propionaldehyde | 2.9 | 17 |
| Propylene | 2.4 | 11 |
| Propylene Oxide | 2.8 | 37 |
| Styrene | 0.9 | 6.8 |
| Tetrafluoroethylene | 4 | 43 |
| Tetrahydrofuran | 2 | 11.8 |
| Toluene | 1.1 | 7.1 |
| Trichloroethylene | 8 | 10.5 |
| Triethylene Amine | 1.2 | 8 |
| Trimethylamine | 2 | 11.6 |
| Turpentine | 0.7 | --- |
| Unsymmetrical dimethylhydrazine | 2 | 95 |
| Vinyl Acetate | 2.6 | 13.4 |
| Vinyl Bromide | 9 | 15 |
| Vinyl Chloride | 3.6 | 33 |
| Vinyl Fluoride | 2.6 | 21.7 |
| Xylene | 0.9 | 7 |
The flammable liquids of most concern in industry and laboratories are those that have flash points below room temperature. These include…
| Solvent | Flash Point (° C) | Flash Point [° F] |
|---|---|---|
| Acetone | -17.8 | [0] |
| Benzene | -11 | [12.2] |
| Carbon disulfide | -29 | [-20.2] |
| Ethanol | 13 | [55.4] |
| Ethyl acetate | 1 | [33.8] |
| Ethyl ether | -45 | [-49] |
| Hexane | -18 | [-0.4] |
| Toluene | 9.5 | [49.1] |
| Xylene (above room temperature—but close enough) | 29 | [84.2] |
Data obtained from various sources, presumed to be reliable, for reference only. In any critical application, double check all parameters, including flammable properties!
AC