From one of the links on Mangetout’s Google search:
So there! I always wondered why they flap their cheeks. (note: I jumped once, and don’t recall breathing, but then again, I don’t recall blinking either. I do recall in detail the feeling when my C2 vertebra was broken by the opening shock.)
I have a vague suspicion that it might be tongue-in-cheek … but I could be wrong, and in any case, it could be taken seriously by readers. Either way, it should probably be removed from the FAQ … or if it is intended as humor, it should be made a bit more obvious.
I was taught in Scuba diving class that one could survive running out of air. The thing to do was to drop your weight belt, which would send you floating toward the surface (assuming you were’nt so deep as to have no bouyancy). The air that remained in the lungs would expand as the pressure dropped, and while some exhaling would be necessary, inhaling would not. (Good thing, since inhaling would also not be possible!) You could expect a case of the bends, but breathing would not be necessary during the ascent because of moving into a lower pressure zone.
While the pressure differential through air is much less than that through water, in the case of skydiving you’re moving into a higher pressure zone. Pretty hard to do that without breathing.
Of course, the main point of the tale in the OP is breathing through your skin. If you’re expecting that to happen, don’t hold your breath (har!).
If you had your mouth open in freefall, would the turbulence produced by the 120 mph winds resuppy oxygen to your lungs or would you still need to inhale and exhale to get the oxygen into your bloodstream?
It may well take longer than the time you could hold your breath, and generally you start after you’ve exhaled, when you discover that no more air is available. The residual oxygen in your lungs is sufficient to sustain you as it becomes available through decompression.
Scuba diving is based on breathing compressed air. You wouldn’t be able to inhale atmospheric pressure-air at the ambient pressure below the surface. (In fact, if your chest is more than one feet deep in water, you can’t inhale atmospheric pressure-air through a tube.) One lungful of the compressed Scuba air might be equal to several lungfuls of non-compressed air. As you rise, it decompresses and expands. If you didn’t exhale, the expanding gasses would burst the lungs.
While there may not be much of lungful left at the time the situation arises, its volume increases as the pressure decreases during the ascent. Not all the oxygen we inhale is used, so there will be some oxygen there. It’s enough, I recall, to keep you supplied through the ascent.