Do scuba divers breath pure oxygen?

Answer 1

Believe it or not, we can die from too little oxygen AND too much oxygen.

This concept involves partial pressures.

If we first consider using standard air (i.e. 20% Oxygen and 80% Nitrogen):

(1 bar = 1 kilogram of pressure per square centimetre)

At the surface - Total Pressure of air = 1 bar

- Pressure of Oxygen = 0.2 bar

- Pressure of Nitrogen = 0.8 bar

At 10m - Total Pressure of air = 2 bar

- Pressure of Oxygen = 0.4 bar

- Pressure of Nitrogen = 1.6 bar

At 20m - Total Pressure of air = 3 bar

- Pressure of Oxygen = 0.6 bar

- Pressure of Nitrogen = 2.4 bar

At 30m - Total Pressure of air = 4 bar

- Pressure of Oxygen = 0.8 bar

- Pressure of Nitrogen = 3.2 bar

At 40m - Total Pressure of air = 5 bar

- Pressure of Oxygen = 1.0 bar

- Pressure of Nitrogen = 4.0 bar

At 50m - Total Pressure of air = 6 bar

- Pressure of Oxygen = 1.2 bar

- Pressure of Nitrogen = 4.8 bar

At 60m - Total Pressure of air = 7 bar

- Pressure of Oxygen = 1.4 bar

- Pressure of Nitrogen = 5.6 bar

At 70m - Total Pressure of air = 8 bar

- Pressure of Oxygen = 1.6 bar

- Pressure of Nitrogen = 6.4 bar

It is at the partial pressure of 1.6 bar (which occurs at 70m where oxygen becomes toxic. That is why most dive organisations recommend 50m as a maximum for recreational diving.

However, if pure oxygen is used:

At surface - Pressure of Oxygen = 1 bar

At 10m - Pressure of oxygen = 2 bar

The oxygen has already become toxic!

Hope that answers your question. The concept is called "partial pressures" and "oxygen toxicity" if you want to research more on a search engine.

Answer 2

Pure oxygen becomes toxic at a pressure of 1.6 atmospheres so once you go below 6 meters you risk an oxygen toxicity event which usuall results in the diver becoming unconcious.

Answer 3

Technical Scuba divers do, but recreational divers do not.