COMPOSITION OF AIR

Composition
Main article: Atmospheric chemistry
Composition of Earth's atmosphere as of Dec. 1987. The lower pie represents the least common gases that compose 0.038% of the atmosphere. Values normalized for illustration.

Mean atmospheric water vapor
Filtered air includes trace amounts of many of the chemical elements. Substantial amounts of argon, nitrogen, and oxygen are present as elementary gases. Note the major greenhouse gases: water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Many additional elements from natural sources may be present in tiny amounts in an unfiltered air sample, including contributions from dust, pollen and spores, sea spray, vulcanism, and meteoroids. Various industrial pollutants are also now present in the air, such as chlorine (elementary or in compounds), fluorine (in compounds), elementary mercury, and sulfur (in compounds such as sulfur dioxide [SO2]).
Composition of dry atmosphere, by volume[5]
ppmv: parts per million by volume
Gas
Volume
Nitrogen (N2)
780,840 ppmv (78.084%)
Oxygen (O2)
209,460 ppmv (20.946%)
Argon (Ar)
9,340 ppmv (0.9340%)
Carbon dioxide (CO2)
383 ppmv (0.0383%)
Neon (Ne)
18.18 ppmv (0.001818%)
Helium (He)
5.24 ppmv (0.000524%)
Methane (CH4)
1.745 ppmv (0.0001745%)
Krypton (Kr)
1.14 ppmv (0.000114%)
Hydrogen (H2)
0.55 ppmv (0.000055%)
Nitrous oxide (N2O)
0.3 ppmv (0.00003%)
Xenon (Xe)
0.09 ppmv (9x10-6%)
Ozone (O3)
0.0 to 0.07 ppmv (0%-7x10-6%)
Nitrogen dioxide (NO2)
0.02 ppmv (2x10-6%)
Iodine (I)
0.01 ppmv (1x10-6%)
Carbon monoxide (CO)
trace
Ammonia (NH3)
trace
Not included in above dry atmosphere:
Water vapor (H2O)
~0.40% over full atmosphere, typically 1%-4% at surface
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