Why do you inhale pure oxygen when diving?

Pure oxygen is not used when diving, but mixed gas is used.

Generally, shallow diving uses compressed air or artificial mixed gas of nitrogen and oxygen.

For deep diving, another artificial helium-oxygen mixture must be used.

This is because the solubility of nitrogen in human blood increases with the increase of diving depth and pressure, and decreases after floating. Nitrogen dissolved in the body will change back to gaseous state and wander around in blood vessels, just like a large number of bubbles are lost during infusion, which will be life-threatening.

Pure oxygen will paralyze the respiratory center of brain stem, and people will stop breathing at this time.

In the same way, the oxygen bottle used in hospital emergency treatment is not pure oxygen, but mixed with 5% carbon dioxide, which is also to prevent the patient from respiratory center paralysis and leading to respiratory stop.