MOLECULAR DENSITY GAS COMP WEIGHT kg/m3 Hydrogen H2 2.016 0.090 Helium He 4.020 0.166 Methane CH4 16.043 0.668 Ammonia NH3 17.031 0.717 Water Vapor, steam H2O 18.016 0.804 Natural gas 19.500 0.700 Neon Ne 20.179 0.900 Acetylene (ethyne) C2H2 26.000 1.092 Carbon monoxide CO 28.010 1.165 Nitrogen N2 28.020 1.165 Ethylene C2H4 28.030 1.260 Air 29.000 1.205 Nitric oxide NO 30.000 1.249 Ethane C2H6 30.070 1.264 Oxygen O2 32.000 1.331 Methyl Alcohol 32.040 Sulfur S 32.060 Hydrogen Sulfide H2S 34.076 1.434 Hydrochloric Acid 36.470 1.630 Hydrogen Chloride HCl 36.500 1.528 Argon Ar 39.948 1.661 Propene (propylene) C3H6 42.100 1.748 Carbon dioxide CO2 44.010 1.842 Nitrous Oxide N2O 44.013 Propane C3H8 44.090 1.882 Nitrogen Dioxide NO2 46.006 Ethyl Alcohol 46.070 Ozone O3 48.000 2.140 Sulfuric Oxide SO 48.063 Methyl Chloride 50.490 Butylene (Butene) C4H8 56.110 2.504 Butane C4H10 58.100 2.489 Nitrous Trioxide NO3 62.005 Sulfur Dioxide SO2 64.060 2.279 Ethyl Chloride 64.520 Chlorine Cl2 70.906 2.994 Methyl Butane 72.150 N-Pentane 72.150 Iso-Pentane 72.150 Carbon disulphide 76.130 Benzene C6H6 78.110 3.486 Sulfur Trioxide SO3 80.062 Cyclohexane 84.160 Hexane 86.170 R-22 86.480 Toluene C7H8 92.141 4.111 N-Heptane 100.200 R-134a 102.030 N-Octane 114.220 R-12 120.920 R-11 137.370 R-123 152.930 R-114 170.930