[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.