ABSTRACT
Atmospheric air is a mixture of oxygen (O2, 20.95%), nitrogen (N2,78.09%), argon (0.93%), carbon dioxide (CO2, 0.03%), and water vapor (0-2%). For practical purposes we usually assume O2, 21% and N2, 79% and ignore the contributions from CO2 and argon. The degree of humidification determines the water vapor pressure and proportional dilution of other gases.
