: if snorkel is 3/4in i.d. and 36in long(this is quite long) get abt 16 cu in.
: which is abt 15% of a 2 litre breath. a factor, but not a real big one.

: what's the driver and at what %, tho'?

I think Pete Notman says it is 16% oxygen. With a 36 inch breathing tube holding about 16 cubic inches (about 250 cc) of esentially iner, or very depleted air (after a few breaths not much oxygen in it), you change the equation a bit.

Each 2 liter breath contains 2 componnts now. the first part of your inhalation is that .25 liter of dead air, and then you get just 1.75 liters of good air. If you need 2 and you only are getting 1.75 for any period of time you are going to eventually drop in the oxygen content of your blood -- and that is what will get you.

Since you'll need some flexibility, connecting the hose to the stern chamber makes more sense. but even there i think you would need about 4 feet of hose, If you connect to the bow chamber you would need about 5 to 6 feet of hose. And the longer you go the worse the effect, and the sooner it will hit you.

Has anyone mentioned that you might get some nasty headaches from oxygen deprivation? They won't kill you but they can slow up your fun for a few hours.

PGJ