AIR

The colorless, odorless, tasteless, gaseous mixture that makes up the earth's Atmosphere. Four gases comprise 99.997 percent (by volume) of clean, dry, air: Nitrogen (78.084 percent); Oxygen (20.946 percent); Argon (0.934 percent); and Carbon Dioxide (0.033 percent). The remaining components include neon, helium, methane, krypton, nitrous oxide, hydrogen, xenon, and various organic vapors. Under normal conditions, air contains up to about 3 percent water vapor (by volume) and many solid, liquid, or gaseous contaminants introduced by human activities and natural causes such as wind erosion and the burning of fossil fuels.