Mixing open circuit gas on the fly

[WillHartNZ]

I've been thinking a bit about Mixed gas diving and came up with a bit of an interesting idea. I'm sure many other people have thought of it and there's probably some major flaw in the concept.

Anyway here goes:

Is it possible mix open circuit gas "on the fly" to ensure the diver is getting the optimal gas mixture for any given depth and reducing unnecessary gas usage? Kind of similar to the way rebreathers mix the gases. In my mind this would also reduce the amount of gas the diver must carry as he will be able to use all his gas at all depths.

Can anyone think of why this wouldn't work?

 

[Wookie]

You'd need fast software, excellent cells, and completely reliable solenoids to make it reality. A failed solenoid in a rebreather means the diver has to manually ad gas. A failed solenoid on a device you are proposing would likely result in someone getting pure helium (resulting in death) or pure O2 (resulting in death) or no gas at all (resulting in death).

That tech doesn't yet exist for my comfort level.

 

[GrimSleeper]

If you use planning software to generate schedules for identical profiles, one using multiple OC gasses and one using CCR at a sensible set-point, you'll find there really isn't a great gain in decompression terms - and therefore time/gas used - from holding a constant pO2 unless the target pO2 is high enough to become risky in terms of oxygen toxicity.

And, as Wookie pointed out, you'd actually have to use a machine that would manage to be more potentially dangerous than a rebreather to do it...


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[Akimbo]

The mixing and monitoring capability is the hard part of a rebreather. Your suggestion basically trades carrying a lot more gas in place of breathing bags (assuming mixing at IP) and CO2 absorbent.

It seems to me that open circuit's advantage of simplicity is lost with what you suggest. You might as well go closed circuit at that point.

 

[Dr. Lecter]

This is easy. Buy a fancy CCR and just put a one-way exhaust valve in the exhale side of the loop. Stupid idea as far as I can see, but you could dial in whatever gas mixture your dil/O2 blend would allow for.