Mine Gases Questions and Answers Basic Principles Specific Gravity

Specific Weight is defined as weight per unit volume. Weight is a force. The Specific Gravity - SG - is a dimensionless unit defined as the ratio of density of the material to the density of water at a specified temperature. The specific gravity of some common gases can be found in the table below:

  • As a reference, normal air has a specific gravity of 1.
  • If the specific gravity is greater than 1 the gas is heavier than air and the vapor will be found low; the larger the number the heavier the gas is and the lower vapors will be found.
  • If the specific gravity is less than 1 the gas is lighter than air and the vapor will be found high; the smaller the number the lighter the gas is and the higher vapors will be found.
  • Various vapors can be "layered" when multiple gasses are present.
Gas Specific Gravity
- SG -
Acetylene (ethyne) - C2H2 0.907
Air 1.000
Ammonia - NH3 0.596
Argon - Ar 1.379
Arsine 2.69
Benzene - C6H6 2.6961
Blast Furnace gas 1.02
Butadiene 1.869
Butane - C4H10 2.0061
Carbon dioxide - CO2 1.5189
Carbon monoxide - CO 0.9667
Carbureted Water Gas 0.63
Chlorine - Cl2 2.486
Coke Oven Gas 0.44
Cyclobutane 1.938
Cyclopentane 2.422
Cyclopropane 1.451
Decane 4.915
Digestive Gas (Sewage or Biogas) 0.8
Ethane - C2H6 1.0378
Ethylene (Ethene) - C2H4 0.9683
Fluorine 1.31
Helium - He 0.138
Heptanes 3.459
Hexane 2.973
Hydrogen 0.0696
Hydrogen chloride - HCl 1.268
Hydrogen sulfide - H2S 1.1763
Isobutane 2.01
Isopentane 2.48
Krypton 2.89
Methane - CH4 0.5537
Methyl Chloride 1.74
Natural Gas (typical) 0.60 - 0.70
Neon 0.696
Nitric oxide - NO 1.037
Nitrogen - N2 (pure) 0.9669
Nitrogen - N2 (atmospheric) 0.9723
Nitrous oxide - N2O 1.530
Nonane 4.428
Octane 3.944
Oxygen - O2 1.1044
Ozone 1.660
Pentane 2.487
Phosgene 1.39
Propane - C3H8 1.5219
Propene (Propylene) - C3H6 1.4523
Sasol 0.42
Silane 1.11
Sulfur Dioxide - SO2 2.264
Toluene-Methylbenzene 3.1082
Water Gas (bituminous) 0.71
Water Vapor 0.6218
Xenon 4.53

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