Hydrogen Safety Part III

Explosion

An explosion cannot occur in a tank or any contained location that contains only hydrogen. An oxidizer, such as oxygen must be present in a concentration of at least 10% pure oxygen or 41% air. Hydrogen can be explosive at concentrations of 18.3-59% and although the range is wide, it is important to remember that gasoline can present a more dangerous potential than hydrogen since the potential for explosion occurs with gasoline at much lower concentrations, 1.1-3.3%. 


Furthermore, there is very little likelihood that hydrogen will explode in open air, due to its tendency to rise quickly. This is the opposite of what we find for heavier gases such as propane or gasoline fumes, which hover near the ground, creating a greater danger for explosion. 

Asphyxiation

With the exception of oxygen, any gas can cause asphyxiation. In most scenarios, hydrogen's buoyancy and diffusivity make hydrogen unlikely to be confined where asphyxiation might occur.

Toxicity/poison

Hydrogen is non-toxic and non-poisonous. It will not contaminate groundwater (it's a gas under normal atmospheric conditions), nor will a release of hydrogen contribute to atmospheric pollution Hydrogen does not create "fumes."

Cryogenic burns

Any cryogenic liquid (hydrogen becomes a liquid below -423°F) can cause severe freeze burns if the liquid comes into contact with the skin. However, to keep hydrogen ultra-cold today, liquid hydrogen containers are double walled, vacuum-jacketed, super insulated containers that are designed to vent hydrogen safely in gaseous form if a breach of either the outer or inner wall is detected. The robust construction and redundant safety features dramatically reduce the likelihood for human contact.