Quote Originally Posted by EricR
You can dive with 100% helium but it is darn expensive. At greater depths you have to replace all of the O2 or as much as you can afford (lots of calculations going on here) as O2 is toxic. If you were to dive with 100% O2 you would go into convulsions at anywhere from 18 to 27 feet. It's all about partial pressures and all kinds of other voodoo.
I never suggested 100% Oxygen.

Are you serious ... Man can exist, breathing 100% helium, with *NO* oxygen?

What about the space program ... where the atmosphere may well be 100% oxygen... at a much reduced pressure? OIr are you relating to *much* increased pressures as would be found in diving?