Hydrogen is a colorless, odorless gas. It is easily ignited. Once ignited it burns with a pale blue, almost invisible flame. The vapors are lighter than air. It is flammable over a wide range of vapor/air concentrations. Hydrogen is not toxic but is a simple asphyxiate by the displacement of oxygen in the air. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket. Hydrogen is used to make other chemicals and in oxyhydrogen welding and cutting. Fuel Hydrogen can be used as a fuel. Rockets Since hydrogen is highly flammable, especially when mixed with pure oxygen, it is used as a fuel in rockets. Usually, they combine liquid hydrogen with liquid oxygen to make an explosive mixture. Chemical processes Hydrogen is an essential part of many chemical processes. Acids and bases Hydrogen atoms are in every acid and base. Hydrogen gas is sometimes used directly to create an acid. For example, it is used in the creation of hydrochloric acid: Fertilizer Hydrogen is important in creating ammonia (NH3) for use in making fertilizer. Food and fat Hydrogen gas is used as a hydrogenating agent to for polyunsaturated fats, such as used in margarine. But it is also used in making unhealthy trans-fats that are often used in cookies and other good.