Gaseous composition of unpolluted air

Unpolluted air is a concept, what the composition of the air would be if man and his works were not on earth. We will never know the precise composition of unp0olluted air because by the time we had means and the desire to determine its composition. The gaseous composition of unpolluted air (dry basis) is given below:

Name of gas	PPM (volume)
Nitrogen	780,900
Oxygen	209,400
Water	-
Argon	9,300
Carbon dioxide	315
Neon	18
Helium	5.2
Methane	1.0-1.2
Krypton	1.0
Nitrous oxide	0.5
Hydrogen	0.5
Xenon	0.08
Organic vapors	Ca. 0.02

The real atmosphere has been more than a dry mixture of permanent gases. It has other constituents – vapor of both water and organic liquids, and particulate matter held in suspension. Above their temperature of condensation, the vapor molecules act just as permanent gas molecules in the air. The predominant vapor in the air has been water vapor.

The gaseous composition of unpolluted air (wet basis) is given below:

Name of gas	PPM (volume)
Nitrogen	756,500
Oxygen	202,900
Water	31,200
Argon	9,000
Carbon dioxide	305
Neon	17.4
Helium	5.0
Methane	0.97-1.16
Krypton	0.97
Nitrous oxide	0.49
Hydrogen	0.49
Xenon	0.08
Organic vapors	Ca. 0.02

The major components of air, nitrogen (78%). Oxygen (20.94%0 and argon (0.93%), do not react with one another under normal circumstances. Similarly, the trace components helium, neon, krypton, hydrogen and nitrous oxide have little or no interaction with other molecules.