Quote Originally Posted by bprewit
When diving I know the compressed air tank has a regulator and the air is fed to the diver at a certain pressure so must you vary this pressure when diving at deeper depths? Do you need "X" amount of pressure to be able to take a breath at "X" depth? Thats off the subject here but was just curious.
The way regulators work is that the 1st stage, which attaches to the tank, supplies air at an "intermediate" pressure, which is around 125psi above the ambient water pressure. So the deeper you go, the more air is delivered to the 2nd stage, which is what you breathe from. This stage supplies air to your lungs at the ambient pressure, which of course increases rapidly with depth. So, basically, you're breathing ALOT more air at depth because your lungs need more air to overcome the surrounding water pressure.

The thing is, O2 supply is almost never the limiting factor in diving time or depth; it's excess nitrogen, which is absorbed into your tissues, and eventually causes disorientation. We never experience this on land because we're breathing far less air at a given time, and our body can expel the nitrogen. At depth, though, it builds up, and pretty soon you have to surface. If you come up too fast or after being down too long, the nitrogen expands in your bloodstream quicker than you can expel it. This is the bends, and actually I've heard that whales occasionally suffer from it if they dive too deep and come up too fast, even though they're only breathing at the surface.

So, unless this system has a way of supplying oxygen to our lungs without nitrogen, I don;t see how it could expand a diver's depth or bottom time.

Edit;
I forgot a couple of things. First, there are current "rebreathers" in use which allow divers to breathe the same air over and over; it gets scrubbed of CO2 and new O2 is injected. Divers who use these love 'em. One great thing is that there are very few bubbles that come out. Anyone who's been diving knows that exhaling bubbles is fairly loud and can spook marine animals, who must have no idea what's going on... just think if you saw someone walking down the street spewing a stream of water with each breath.

The other thing is, great post Tim! I always kind of wondered about that liquid breathing thing in The Abyss.