How high can you go in a normally aspirated

[Jim Rainer]

Wayne, I stick to the regs, no more than 30 minutes if at 12,500 and no higher without O2. Actually, as long as I have a kit on board, I put the mask on at 10K. At night, I'll put it on above 6K. May not be necessary but it makes one feel more refreshed. O2 is cheap. About $15 for a filluip at the scuba dive shop. Incidentally, I am and have been a non-smoker all my life and in good physical codition. I think there is a lot of variation in people as far as O2 is concerned.