The explosive limit of a gas or a vapour, is the limiting concentration (in air) that is needed for the gas to ignite and explode. This page is about the physical properties of gas as a state of matter A vapor or vapour (see Spelling differences) is a substance in the Gas phase at a Temperature lower than its Critical temperature In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release There are two explosive limits for any gas or vapor, the lower explosive limit (LEL) and the upper explosive limit (UEL). At concentrations in air below the LEL there is not enough fuel to continue an explosion; at concentrations above the UEL the fuel has displaced so much air that there is not enough oxygen to begin a reaction. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Concentrations of explosive gases are often given in terms of percent of lower explosive limit (%LEL).
A deflagration is a propagation of a combustion zone at a velocity less than the speed of sound in the unreacted medium. A detonation is a propagation of a combustion zone at a velocity greater than the speed of sound in the unreacted medium. An explosion is the bursting or rupture of an enclosure or container due to the development of internal pressure from a deflagration or detonation. As defined in NFPA 69.
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Gases and vapours
Controlling gas and vapor concentrations outside the explosive limits is a major consideration in occupational safety and health. Occupational safety and health is a cross-disciplinary area concerned with protecting the Safety, Health and welfare of people engaged in Methods used to control the concentration of a potentially explosive gas or vapor include use of sweep gas, an unreactive gas such as nitrogen or argon to dilute the explosive gas before coming in contact with air. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 This article pertains to the chemical element For other uses see Argon (disambiguation. Use of scrubbers or adsorption resins to remove explosive gases before release are also common. Adsorption is a process that occurs when a gas or liquid Solute accumulates on the surface of a solid or a liquid (adsorbent forming a film of molecules or atoms (the Gases can also be maintained safely at concentrations above the UEL, although a breach in the storage container can lead to explosive conditions or intense fires. Fire is the heat and light energy released during a Chemical reaction, in particular a combustion reaction.
Dusts
Dusts also have upper and lower explosion limits, though the upper limits are hard to measure and of little practical importance. Lower explosive limits for many organic materials are in the range of 10–50 g/m³, which is much higher than the limits set for health reasons, as is the case for the LEL of many gases and vapours. Dust clouds of this concentration are hard to see through for more than a short distance, and normally only exist inside process equipment.
Explosion limits also depend on the particle size of the dust involved, and are not intrinsic properties of the material. In addition, a concentration above the LEL can be created suddenly from settled dust accumulations, so management by routine monitoring, as is done with gases and vapours, is of no value. The preferred method of managing combustible dust is by preventing accumulations of settled dust through process enclosure, ventilation, and surface cleaning. However, lower explosion limits may be relevant to plant design.
Examples
The explosive limits of some gases and vapors are given below. Concentrations are given in percent by volume of air.
| Substance | LEL | UEL |
|---|---|---|
| Acetone | 3% | 13% |
| Acetylene | 2. Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless mobile flammable Acetylene ( IUPAC name ethyne), C2H2 is a Hydrocarbon belonging to the group of Alkynes It is the simplest of all alkynes 5% | 82% |
| Benzene | 1. Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 2% | 7. 8% |
| Butane | 1. Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 8% | 8. 4% |
| Ethanol | 3% | 19% |
| Ethylbenzene | 1. Ethylbenzene is an Organic compound with the formula C6H5CH2CH3 0% | 7. 1% |
| Ethylene | 2. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. 7% | 36% |
| Diethyl ether | 1. Diethyl ether, also known as ether and ethoxyethane, is a clear colorless and highly Flammable liquid with a low Boiling point and a 9% | 36% |
| Diesel fuel | 0. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum 6% | 7. 5% |
| Gasoline | 1. 4% | 7. 6% |
| Hexane | 1. Hexane is an Alkane Hydrocarbon with the Chemical formula CH3(CH24CH3 or C6H14 1% | 7. 5% |
| Heptane | 1. n -Heptane is the straight-chain Alkane with the Chemical formula H3C(CH25CH3 or C7H16 05% | 6. 7% |
| Hydrogen | 4% | 75% |
| Hydrogen sulfide | 4. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Hydrogen sulfide (or hydrogen sulphide) is the Chemical compound with the formula H 2 S. 3% | 46% |
| Kerosene | 0. Kerosene, sometimes spelled kerosine in scientific and industrial usage is a Combustible Hydrocarbon liquid 6% | 4. 9% |
| Methane | 4. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. 4% | 17% |
| Octane | 1% | 7% |
| Pentane | 1. Octane is a straight-chain Alkane with the Chemical formula CH3(CH26CH3 Pentane is any or one of the Organic compounds with the formula C5H12 5% | 7. 8% |
| Propane | 2. Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable 1% | 9. 5% |
| Propylene | 2. Propene, also known as propylene, is an unsaturated organic compound having the Chemical formula C 3 H 6 0% | 11. 1% |
| Styrene | 1. Styrene, also known as vinyl benzene as well as many other names (see table is an Organic compound with the Chemical formula C6H5CH=CH2 1% | 6. 1% |
| Toluene | 1. Toluene, also known as methylbenzene or phenylmethane, is a clear water -insoluble liquid with the typical smell of Paint thinners redolent of 2% | 7. 1% |
| Xylene | 1. o-Xylene|m-Xylene|p-XyleneThe term xylene or xylol refers to a mixture of three Benzene derivatives which is used as a Solvent in the Printing 0% | 7. 0% |
See also
References
- David R. Flammability limits, also called flammable limits or explosive limits give the proportion of combustible Gases in a mixture between which limits Lide, Editor-in-Chief; CRC Handbook of Chemistry and Physics, 72nd edition; CRC Press; Boca Raton, Florida; 1991; ISBN 0-8493-0565-9
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