The funny thing is that 3000 years ago you wouldn’t get burned at the stake for thinking like that.

That’s easy to check. I’m currently insanely jet lagged and super tired, yawning every few minutes. My pulse oximeter is indicating 99% saturation, so that’s not it.

Edit: on the other hand, I’m a flight attendant, so my body is used to lower oxygen atmospheres, so I usually have >98% O2 levels.