Gas Symbol MolecularWeight

Volume %

Basic constituentsNitrogen N2 28.013 78.084 0.004 %Oxygen O2 32.0 20.946 0.002 %Argon Ar 39.948 0.934 0.001 %

Trace gasesNeon Ne 20.183 18.12 0.04 ppmHelium He 4.003 5.239 0.05 ppmKrypton Kr 83.80 1.14 0.01 ppmXenon Xe 131.30 0.087 0.001 ppmHydrogen H2 2.016 0.5 0.01 ppm

ImpuritiesWater H2O 18.015 0.1 2.8 %Carbon dioxide CO2 44.011 300 30 ppmMethane CH4 16.043 1.5 to 2.5 ppmCarbon monoxide CO 28.010 0.061 to 1.1 ppmSulphur dioxide SO2 64.06 1.1 ppmNitrous oxide N2O 44.012 0.5 ppmOzone O3 47.998 0.011 to 0.11Nitrogen dioxide NO2 46.005 0.005 to 0.02 ppmRadon Rn 222 TraceNitric oxide NO 30.006 Trace

Openshaw, D. and Cain, S., "Ultra-pure Cryogenic Nitrogen Generator", TCE, TheChemical Engineer, The Institution of Chemical Engineers, Rugby, England, UK.,November 2002, p. 30.

FIG. 1-9Gaseous Composition of Air

=Alpha

=Beta =Gamma

=Delta

=Epsilon

=Zeta =Eta

=Theta

=Iota

=Kappa

-Lambda

=Mu

=Nu

=Xi =Omicron

=Pi

=Rho

=Sigma

=Tau

=Upsilon

=Phi =Chi

=Psi

=Omega

FIG. 1-10Greek Alphabet

1-15