At higher altitudes (Flight Levels) even 100% O2 is not sufficient. It must
be delivered under pressure through a secure O2 mask.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
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"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? I guess it might be cumulative, i.e. the longer
you go at 92% the less safe it is? Dropped down to about 88% when I
got distracted with some cockpit chores and started normal sea level
breathing.