Its a bit more complicated than that. Smokers with lung disease who become "carbon dioxide retainers" can tolerate low levels of oxygen and actually become drowsy when given too much oxygen (when I say too much, if I was given that much oxygen I wouldn't be affected).Sea Skimmer wrote:Smokers can fall asleep easily enough even without drinking. The mere act of laying down is what does it, should you be dumb enough to do that at all. No real surprise since smoking = oxygen deprivation = drowsiness.
Moreover while I don't know the exact numbers or the exact cut off, it is said that hypoxia tends to manifest as agitation rather than drowsiness, although it can do both (at least this was the reasoning given in a past exam paper why a patient's confusion is less likely to be due to hypoxia). Obviously if the oxygen level gets to zero I think its safe to say people will be unconscious.