The most used gases in therapies and surgery are oxygen and nitrogen protoxide. The first one can be excessively present, either because of a hyperbaric chamber, or because of a leak from the normal distribution system. The second one is a common anaesthetic, which obligatorily need to be supervised in the operating room.
Oxygen (O2): leaks might occur because of a mechanic interruption of the pipes and of the distributors.
Nitrogen protoxide (N2O): it is only used as anaesthetic in the operating room. A leak of this gas during an operation can seriously compromise all the presents and the result of the operation itself.
O2: both excess and lack of oxygen may cause important diseases, sometimes death.
N2O: at ordinary temperature and pressure it is a colourless, non flammable gas with a slightly sweet odour. It is widely used in medical applications as analgesic and anaesthetic. It is also known as laughing gas for its euphoric effects.