biglove wrote: ↑
September 18th 2019, 6:58pm
Didn’t watch the video, knew Bedlam would give us the real stuff and he did. Never understood the ins and outs of mixed gas diving. Now I have a basic grasp.
This place and the Lords are what a forum should be.
Cheers Bigs :-)
I will add to my post a couple of things.
The reason you see guys doing deep dives with multiple tanks is that every breath you take at 40m uses 5x as much air as you would at sea level...which means you use your tanks up quickly when you are deep. So they might take a couple of tanks to compensate.
Also, if you dive really deep you need to start with only a tiny amount of oxygen in the mix at the top. At 100m you are getting 11 atmospheres of pressure. For a 100m dive you might use a 10% O2 mix. You can't breathe that at the surface so you would have that clipped off somewhere on your body and you would take another tank with at least 16% O2 as a 'travel gas' to get you deep enough to start using the low-O2 (anoxic) cylinder.
You would also carry additional cylinders with high O2 concentrations (50% - 100%) so that when you come close to the surface (around 6m) you can use the high O2 gas to flush the nitrogen out of your system quickly and reduce the time you need to 'off-gas' in decompression.
So for 100m dive you might have 5 tanks attached; 1 cylinder for travel gas to get down, 2 anoxic tanks for the deep bit, 1 nitrox to start early on decompression as you ascend, and 1 100% O2 deco tank for near the surface to reduce deco time.