Air, Composition
Air, Composition : of. Dry atmospheric air contains the following gases in the proportions (by weight) indicated: Nitrogen 75. 5; Oxygen 23. 2; Argon 1. 3; Carbon Dioxide 0. 05-0. 4; Krypton 0. 028; Xenon 0. 005; Neon 0. 00086; Helium 0. 000056. By volume, air contains 21% oxygen, 78. 5% nitrogen; 0. 3% carbon dioxide. For all Fire Service calculations, however, the lesser gases are usually ignored, nitrogen, oxygen and carbon dioxide only being considered