Question

Choose the correct answer from the alternatives given in the brackets.
The mixture of gases used by deep sea divers is _______ .
(Helium-Oxygen, Oxygen-Nitrogen)

Answer 1

Oxygen is toxic at sufficient partial pressure. Scuba divers use a soft suit and breathe an air mixture at ambient pressure, which increases with depth, so that pure oxygen is toxic at depths below I think about 10 metres. Nitrogen is not toxic, but at pressure engenders depression so that extended use is not recommended. Helium is neither toxic nor narcotic so they use helium oxygen mixture.