(Chemical formula: CO2). A colorless, odorless, noncombustible gas used in several welding processes; supplied in cylinders, shipped at its vapor pressure of 5722 kPa (830 psig) at 21°C (70°F). Molecular weight: 44.011; specific gravity: 1.522 at 21°C (70°F);critical pressure: 1183 kPa (171.6 psia).