What do tech divers breathe? | Answered |

[@pauldawson2902]

Great, thanks. As an oldie I was taught 'always keep breathing', you have gone with 'never hold your breath when ascending' Did that change at the same time as the quarter turn rule?

[@pucioy]

Mark, I got a funny question which I cannot find answer to. I talked about it with divers and physicists and I got a different answers. None of them was clear and convincing. Imagine that we have huge pipe ( let's say 20m long and diameter 3m) mounted vertically in the lake. 5m of the pipe is under water and 15m is sticking out over the surface. Of course if top of the pipe is open, water level in the pipe is the same as water level outside of the pipe. Now comes funny part. What depth is gonna be shown on a dive computer of diver who is in the pipe on the level of outside water but we closed the top of the pipe and pomped out the air ? Of course when we pumped out the air, level of water in the pipe is much higher then outside so actually diver being on the level of surface of outside water is still deep underwater inside the pipe. Just funny riddle...:)))

[@mohawkdroid69]

#askmark I fully understand the portion of don't hold your breath and rise. What is the problem with holding your breath and descending? As long as I've taken a few deep breaths from the reg, air supply, and everything is confirmed. What's the harm in holding my breath to descend like when I freedive?

[@Yggdrasil42]

Remember that the gas in your lungs will shrink as outside pressure increases. If you would descend from the surface to 40m your lungs would have to shrink to 1/5 th the size (1 bar vs 5 bar of ambiend pressure). Yes lungs are flexible but they're not tough. Freedivers do this kind of thing regularly so I'm not sure it's bad for you but I read that the lungs of extreme freedivers fill with plasma from their blood on descent which gets reabsorbed on ascent. Doesn't sound great to me.

[@nyax129]

Come on mark. It's about the black

[@nickpaulie]

How regulate how much volume and what type of gas to be in the bottles. Because I seen compressors for filling of bottles there is just one item to connect the bottle-where is the switch to helium or other type of gas or there is other types of compressors?

[@Yggdrasil42]

Other types of compressors for Nitrox (for higher O2 percentages) and groups of large cylinders (buffers) filled with pure O2 and pure Helium. The operator mixes the desired gas mix from those sources. For example they fill the tank partially with pure oxygen from a buffer tank then add compressed air from the compressor to dilute it to the desired mix. They use apps (or tables) to calculate how much of which gas to use.

[@marioschmitt4435]

#askmark Is there any rule, like ISO regulations for autonomous diver, that is necessary to conduct deco dives? Don’t get me wrong, common sense should say, don’t do, what you haven’t been trained to, yet is there any regulation preventing recreational divers from doing a planned deco dive? No worries, am doing tech training at moment, not planning to exeed my limits in any way.