What happens when you suffocate long enough to pass out? Let's say you had the self control to hold your breath long enough, or if you smothered yourself for long enough, to lose consciousness. How long will the unconsciousness last if you weren't revived? Will you wake up with a headache or some hangover-type symptoms (not an actual hangover, obviously, because you suffocated, not dehydrated)? Could it do any permanent (or semi-permanent) damage provided that you don't crash down and break something? What state of mind would you be in while unconscious? Similar to sleeping? Would you dream? Would you remember it? On a related note... What about other ways of forcing yourself into an unconscious state? Such as doing that head-rush trick? (If you don't know, you stand bent over with your head down for a minute or so, then quickly straighten up to a standing position. If you do it right, you will lose consciousness. Good party trick ) How would the effects differ from asphyxiation?