That they recognize. The human factors literature, NASA research, etc is pretty clear that someone who lives in a non-mountainous area will start to have effects somewhere between 4,000 and 8,000 feet ASL. That's the reason why airliners are pressurized to what they are. More importantly, that's why NASA treats a 5,000 ft cabin altitude as only marginal.Somewhere right around 10k is where most people start having effects
Of course. It doesn't need to be fancy to work.OK, a canula then combined with cabin heat. Not a significant' system
I know. I just wanted to point out a couple of things. Sorry for the derail.My point was if you want to dabble in that altitude regime then it is less complex than much higher.