[nradov]

That's mostly correct but your body doesn't metabolize oxygen based on the partial pressure. The actual rate of oxygen metabolism depends mostly on activity level regardless of depth or PPO2.

Your body can function pretty well at PPO2 levels less than 0.17 bar. People go to an altitude of 10000 ft / 3000 m all the time where PPO2 is only 0.14 bar.

[ddls]

0.17 is a rule of thumb we use in diving. There are many like it which allow a little leeway in case there's a slip-up. pp02 can surely go higher than 1.2 (I know personally) before causing problems in some people. That said, I bet if you're climbing at 0.14 bar that you've stashed a pony bottle of 100% oxygen somewhere in your kit, just in case, no ?

[nradov]

People live and work just fine at 0.14 bar PPO2, no supplemental oxygen required. Aerobic capacity will be reduced. 10000 ft is the usual limit for requiring supplemental oxygen in aviation.