SparticleBrane:I didn't quite word it as well as I hoped, sorry.
The question still stands, though--would he be able to donate it if it was under his waist strap? Personally I'd rather not be the guy who needs air in that situation.
From the waist strap to the 2nd stage is about 3' of hose. Even if it you couldn't get it out of the strap, there's more than enough hose. BTW, fully deploying the long hose is part of the pre-dive check.