Classification of Air Contaminants - Brochure

Under natural circumstances, the air we breathe contains (by volume) approximately 78% nitrogen, 21 % oxygen and trace amounts of argon, neon, helium, krypton, hydrogen, nitrous oxide and xenon as permanent gases. Variable gases in the atmosphere are water vapour (0 to 7% by volume), carbon dioxide (.03%) and much smaller amounts of methane, carbon monoxide, ozone, ammonia, nitrogen dioxide, sulphur dioxide and hydrogen sulphide. The atmosphere is also a host to natural atmospheric impurities in the form of particles and gases that originate from wind erosion, sea spray evaporation, volcanic eruption and biological processes such as sporing and pollinating.