Is Po2 only something to worry about if diving enriched o2?

[dmaziuk]

What is the danger of a low Po2

The danger is we can only feel excess CO2, we can't feel lack of oxygen. We just pass out with no, or very little, warning.

There's a thread in Accidents about kids jumping in a pool with a tank of pure helium, IIRC some of the posters there say they black out after as few as four breaths of pure He (i.e. ppO2 = 0).

 

[boulderjohn]

Since previous posts have things covered, I want to discuss a low PO2 possibility that has not been covered--using plain air.

If you were to come diving with me in either Colorado or New Mexico and set your computer for using air, your alarm will sound. You will get a low PO2 warning while still on the surface. That is because air thins out at altitude, and that New Mexico/Colorado diving locations, total air pressure has dropped enough so that the oxygen partial pressure will be below that level that you have been warned will kill you. It is, however, what we breathe every day, and we live through that. We also go into the mountains, where we continue to breathe even lower POs and still survive. When you are at the surface and the computer gives you that alarm, you will have been breathing that PO2 for a long time already.

If you are breathing air at .17 and descend 10 feet, you will be breathing the equivalent of air at sea level.

I do not advocate breathing hypoxic mixes without proper training, but if you were to fill your tank with .14 PO2 and descend 17 feet, you will be breathing the equivalent of air at sea level.

My computer allows me to change the default warning PO2 to a lower level.

 

[ssssnake529]

That is good information to be aware of. Thanks for that.

Since previous posts have things covered, I want to discuss a low PO2 possibility that has not been covered--using plain air.

If you were to come diving with me in either Colorado or New Mexico and set your computer for using air, your alarm will sound. You will get a low PO2 warning while still on the surface. That is because air thins out at altitude, and that New Mexico/Colorado diving locations, total air pressure has dropped enough so that the oxygen partial pressure will be below that level that you have been warned will kill you. It is, however, what we breathe every day, and we live through that. We also go into the mountains, where we continue to breathe even lower POs and still survive. When you are at the surface and the computer gives you that alarm, you will have been breathing that PO2 for a long time already.

If you are breathing air at .17 and descend 10 feet, you will be breathing the equivalent of air at sea level.

I do not advocate breathing hypoxic mixes without proper training, but if you were to fill your tank with .14 PO2 and descend 17 feet, you will be breathing the equivalent of air at sea level.

My computer allows me to change the default warning PO2 to a lower level.