Sea level concentrations of the six principal constituents of dry and staurated air are given below. Dry air is often obtained by drying compressed atmospheric air using a suitable drying agent. In some cases dry air is made up in cylinders using 20.95 mol% oxygen with the balance being exclusively nitrogen. Care should be taken that argon is not analyzed as oxygen, as can occur in GC analysis. Dry air contains a higher concentration of oxygen than atmospheric air, which contains moisture. The absolute humidity of saturated air is found using steam tables. For example, saturated air at 100 degrees F contains 6.46 mol% water vapor. Relative humidity at any temperature is the fraction of the water vapor concentration corresponding to saturation. Constituent Gases [Dry Air (mol%), Sat Air @ 100 degrees F(mol%)]; Nitrogen (78.09, 73.04), Oxygen (20.95, 19.60) Water (0.00, 6.46), Argon (0.93, 0.87), Carbon Dioxide (0.030, 0.028), Neon (0.0018, 0.0017), Helium (0.000524, 0.00049)
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