Gaseous composition of dry air.


Constituent Chemical symbol Mole percent
Nitrogen N2 78.084
Oxygen O2 20.947
Argon Ar 0.934
Carbon dioxide CO2 0.0350
Neon Ne 0.001818
Helium He 0.000524
Methane CH4 0.00017
Krypton Kr 0.000114
Hydrogen H2 0.000053
Nitrous oxide N2O 0.000031
Xenon Xe 0.0000087
Ozone* O3 trace to 0.0008
Carbon monoxide CO trace to 0.000025
Sulfur dioxide SO2 trace to 0.00001
Nitrogen dioxide NO2 trace to 0.000002
Ammonia NH3 trace to 0.0000003

* Low concentrations in troposphere; ozone maximum in the
30- to 40-km regime of the equatorial region.

Mackenzie, F.T. and J.A. Mackenzie (1995) Our changing planet. Prentice-Hall, Upper Saddle River, NJ, p 288-307.
(After Warneck, 1988; Anderson, 1989; Wayne, 1991.)