Air is considered the mixture of gases that make up the earth's atmosphere. The principal gases that compose dry air are Nitrogen (N2) at 78.09%, Oxygen (O2) at 20.946%, Argon (A) at 0.93%, and Carbon Dioxide (CO2) at 0.033%. One of the most important variable constituents of air and most important gases in meteorology is water vapor (H2O), which may vary between zero and about four per cent.
Other components are traces of Neon (Ne), Helium (He), Methane (CH4), Krypton (K), Hydrogen (H), Nitrous Oxide (N2O) and Xenon (Xe)
