What's minimum safe O2 level?

"PaulH" wrote in message
om...
I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime?

It all depends on the individual, but 90% saturation is considered about the
safe minimum.

The effects ARE cumulative over time, hence the 30 minutes granted for
operations without oxygen between 12,500' and 14,000'. However, IMHO at a
safe saturation level the main effects of extended time without supplemental
O2 have to do with fatigue, leading to secondary impairment, rather than
impairment due directly to hypoxia.

All that said, the bottom line is that even at 10,000' anyone can benefit
from supplemental oxygen. If nothing else, you'll feel better after a long
flight, and you may find that mental tasks are actually easier.

Pete