Hydrogen (H2)
Hydrogen gas is odourless and colourless, mixes well with air and explosive mixtures are easily formed. Heating may cause violent combustion or explosion. Reacts violently with air, oxygen, halogens and strong oxidants, causing fire and explosion hazard. Metal catalysts, such as platinum and nickel, greatly enhance these reactions.
The substance can be absorbed into the body by inhalation, and is a simple asphyxiant. High concentrations in the air cause a deficiency of oxygen with the risk of unconsciousness or death.