| Lower
and Upper Explosive Limits for Flammable Gases and Vapors (LEL/uel) |
| 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 support 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. |
| 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, 6th edition, copyright 1980 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 |
LEL
|
UEL
|
|
Gas |
LEL
|
UEL
|
| Acetone |
2.6 |
13.0 |
Heptane |
1.1 |
6.7 |
| Acetylene |
2.5 |
100.0 |
Hexane |
1.2 |
7.4 |
| Acrylonitrile |
3.0 |
--- |
Hydrogen |
4.0 |
75.0 |
| Allene |
1.5 |
11.5 |
Hydrogen
Cyanide |
5.6 |
40.0 |
| Ammonia |
15.0 |
28.0 |
Hydrogen
Sulfide |
4.0 |
44.0 |
| Benzene |
1.3 |
7.9 |
Isobutane |
1.8 |
8.4 |
| 1,3-Butadiene |
2.0 |
12.0 |
Isobutylene |
1.8 |
9.6 |
| Butane |
1.8 |
8.4 |
Isopropanol |
2.2 |
--- |
| n-Butanol |
1.7 |
12.0 |
Methane |
5.0 |
15.0 |
| 1-Butene |
1.6 |
10.0 |
Methanol |
6.7 |
36.0 |
| Cis-2-Butene |
1.7 |
9.7 |
Methylacetylene |
1.7 |
11.7 |
| Trans-2-Butene |
1.7 |
9.7 |
Methyl
Bromide |
10.0 |
15.0 |
| Butyl
Acetate |
1.4 |
8.0 |
3-Methyl-1-Butene |
1.5 |
9.1 |
| Carbon
Monoxide |
12.5 |
74.0 |
Methyl
Cellosolve |
2.5 |
20.0 |
| Carbonyl
Sulfide |
12.0 |
29.0 |
Methyl
Chloride |
7.0 |
17.4 |
| Chlorotrifluoroethylene |
8.4 |
38.7 |
Methyl Ethyl
Ketone |
1.9 |
10.0 |
| Cumene |
0.9 |
6.5 |
Methyl
Mercaptan |
3.9 |
21.8 |
| Cyanogen |
6.6 |
32.0 |
Methyl Vinyl
Ether |
2.6 |
39.0 |
| Cyclohexane |
1.3 |
7.8 |
Monoethylamine |
3.5 |
14.0 |
| Cyclopropane |
2.4 |
10.4 |
Monomethylamine |
4.9 |
20.7 |
| Deuterium |
4.9 |
75.0 |
Nickel
Carbonyl |
2.0 |
--- |
| Diborane |
0.8 |
88.0 |
Pentane |
1.4 |
7.8 |
| Dichlorosilane |
4.1 |
98.8 |
Picoline |
1.4 |
--- |
| Diethylbenzene |
0.8 |
--- |
Propane |
2.1 |
9.5 |
| 1,1-Difluoro-1-Chloroethane |
9.0 |
14.8 |
Propylene |
2.4 |
11.0 |
| 1,1-Difluoroethane |
5.1 |
17.1 |
Propylene
Oxide |
2.8 |
37.0 |
| 1,1-Difluoroethylene |
5.5 |
21.3 |
Styrene |
1.1 |
--- |
| Dimethylamine |
2.8 |
14.4 |
Tetrafluoroethylene |
4.0 |
43.0 |
| Dimethyl
Ether |
3.4 |
27.0 |
Tetrahydrofuran |
2.0 |
--- |
| 2,2-Dimethylpropane |
1.4 |
7.5 |
Toluene |
1.2 |
7.1 |
| Ethane |
3.0 |
12.4 |
Trichloroethylene |
12.0 |
40.0 |
| Ethanol |
3.3 |
19.0 |
Trimethylamine |
2.0 |
12.0 |
| Ethyl
Acetate |
2.2 |
11.0 |
Turpentine |
0.7 |
--- |
| Ethyl
Benzene |
1.0 |
6.7 |
Vinyl
Acetate |
2.6 |
--- |
| Ethyl
Chloride |
3.8 |
15.4 |
Vinyl
Bromide |
9.0 |
14.0 |
| Ethylene |
2.7 |
36.0 |
Vinyl
Chloride |
4.0 |
22.0 |
| Ethylene
Oxide |
3.6 |
100.0 |
Vinyl
Fluoride |
2.6 |
21.7 |
| Gasoline |
1.2 |
7.1 |
Xylene |
1.1 |
6.6 |
|
|
