Hydrogen Dangers

Hydrogen is the most abundant chemical element in the universe. On Earth, it is mostly found in numerous compounds. At ordinary temperatures and pressures, the free element takes the form of a colorless, odorless gas. Its dangers are associated with extreme flammability and its reactivity with other elements.

Combustion in Air

• Hydrogen burns readily in air over a wide range of concentrations (from 4 percent to 75 percent by volume). This process, called combustion, involves the reaction of hydrogen with oxygen, and produces water and a large amount of heat. If allowed to expand rapidly from a high-pressure cylinder, hydrogen can ignite spontaneously in air.

Explosive Mixture with Oxygen

• Hydrogen forms an explosive mixture with oxygen. A pure hydrogen-oxygen flame is nearly invisible and can be very dangerous.

Reactions with Chlorine and Fluorine

• Hydrogen also reacts violently with chlorine and fluorine, which are strong oxidants.

Asphyxiant

• When present at high concentrations in the air, hydrogen can act as an asphyxiant.

Comparison with Gasoline

• Gasoline and hydrogen are highly flammable. But gasoline can spill onto materials that might then ignite. By contrast, if hydrogen leaks out of a tank, it quickly disperses and rises through the air, minimizing the chances of catching fire.

Safe Storage

• Hydrogen can be safely stored and transported in specially designed pressurized cylinders or tanks.