# Re: Clarification

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Posted by John Walker on February 02, 2001 at 23:52:41:

In Reply to: Clarification posted by mattschechter on February 02, 2001 at 22:24:26:

!.6 is more than enough oxygen. Think of it this way. At sea level you take in only .21 oxygen. 1.6 is a combined fraction of oxygen. Example: .21 or 21% oxygen goes into 1.6, 7.61 times.

Each 33' of sea water is 1 atm (atmosphere).

Add another 1 atm to the surface pressure and you get another atmosphere

In diving ( and physics) we call this atmosphers absolute

33 feet salt water (fsw) is 1 atmosphere water plus one atmoshere at the earths surface. This equals 2 ATA or 2 atmospheres absolute, same thing.

If we breathe air at the surface (sea level= 1 ATM) we breathe almost .21 or 21% oxygen. At 33 feet salt water (fsw) we are at 2 atmospheres absolute. 1 atmosphere(atm) of sea water pressure plus 1 atmosphere for sea level pressure. This equals 2 atmospheres absolute ( or 2 atm)

If air has a fraction of .21 or 21% oxygen then multiply that by ATM's or Atmospheres absolute.

Air has a pressure of oxygen of PO2.21 at the surface.

At 33 fsw the pressure of O2 is doubled at .42
2 ata * .21 = .42

At 66 fsw the pressure of O2 increases 1 more atm and is .63.
3 ata * .21 = .63

We call this a pO2 or a ppO2 for pressure (p) of O2 or (pp) Partial Pressure of O2.

Hope this helps, John

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