Hydrogen Gas H2 UN1049 Hydrogen gas is colorless, odorless, tasteless, flammable, and nontoxic. Hydrogen gas exists as a gas at ambient temperatures and atmospheric pressures. Hydrogen gas is the lightest gas known with a density approximately 0.07 that of air. The concentration of hydrogen gas in the atmosphere volume is 5.0 x 10-5%. Hydrogen is principally shipped and used in gaseous form for refineries, petrochemical companies for hydrotreating, catalytic reforming and hydrocracking. Hydrogen is also used in heat treating, metal production, welding, lasers, plastics, food production, and semiconductors. Download Hydrogen PDF   previous - Helium-3 Gas next - Krypton Gas