Our respiratory air consists of up to 78 % volume of nitrogen. It is odourless,
colourless and it normally does not contribute to chemical reactions. The danger of
nitrogen lies in the fact that in enclosed rooms it displaces the oxygen component.
As the human respiratory reflex does not react to a lack of oxygen but to an accumulation
of carbon dioxide, we do not receive any warning signals. Loss of consciousness and
asphyxiation merge into one another unnoticed.