Argon

Argon is used because of its inert properties for protection against the oxidizing effect of air. Argon is widely used as a blanketing or shielding gas in metallurgy and arc welding and cutting. Argon is also used to fill incandescent and fluorescent lamps and windows.
Argon is a colorless, odorless, tasteless and nontoxic gas. Argon, along with helium, neon, krypton, xenon and radon is also known as a "rare" gas. Argon forms no known chemical compounds. The gas is 1.38 times heavier than air and is slightly soluble in water. Argon is present in the atmosphere at a concentration of 0.93%. Argon is recovered from air in an Air Separation Unit (ASU) where it is drawn off as a cryogenic liquid at about -303°F. Argon can then be distributed as a cryogenic liquid or as a gas in cylinders.