What do you think about the possibility of using hydrogen as a buffer gas (is that the right term? I haven't looked into this stuff in a good long time...). H/O mixtures are only explosive over a fairly narrow range, so it should be perfectly safe to breathe once the total pressure (And thus hydrogen fraction) are high enough, and I know I've seen it proposed in science fiction, but I'd be interested to know what an actual diver thinks about it.
Commercial diving operations have used hydrogen mixes on an experimental basis for extremely deep dives. This was done mainly to reduce the work of breathing, not to save helium. At extreme depths of like 400m even helium gas gets thick and hard to breathe, whereas hydrogen is a little less dense. Nowadays most work at 400m+ is done by ROVs instead of human divers due to cost and safety.
For sport diving in the 30 – 120m range using hydrogen mixes would be ridiculously dangerous due to the fire risk. What happens if your tank leaks on the dive boat next to an engine? No sane dive shop owner or boat captain would ever allow it.
> What happens if your tank leaks on the dive boat next to an engine?
Nothing much would happen, the hydrogen would rapidly rise up and away.
You'd have a hard time intentionally causing a fire with a low level leak of hydrogen near a closed fire like an engine, never mind by accident.
A small amount of safety precaution (and diving is quite full of safety precautions, so I think they could handle it) is all you would need to make it safe.
You're kidding right? I tell you what, how about you mix up a tank of 18% O₂ / 45% H / 37% N₂ pressurized to 230bar. Then open the tank valve next to an old outboard motor or a deckhand smoking a cigarette.
Sport diving with flammable mixes is something that only works in hacker fantasy land, not the real world.
Smoking would be bad because the fire would be amongst the tanks, but you'd have to open it almost on top of the motor to cause a fire that way, because the fire in contained, and the hot part (the exhaust) is under water. Plus the motor is not located where the people/supplies are.
So simply don't carry the tank over to the motor and open it there, and don't smoke. Even the most basic of safety practice would make this not a problem.
Do you not carry any fuel onboard? Hydrogen is safer than gasoline, yet people carry it without a second thought.
