HVACR Glossary

Air
The elastic, invisible mixture of gases that surrounds the earth. It is composed of 78% nitrogen, 21% oxygen, and 1% rare gases including carbon dioxide, krypton, neon, argon, ozone, helium, and ammonia. Also called atmosphere. One Btu will raise the temperature of 55 cubic feet of air 1 F. Also see ambient, atomizing, combustion, compressed, excess, induced, preheated, primary, seal, secondary, and ventilation air.