in the main to divers on some form of Nitrox (air, EANx, etc).
Trimix is much lighter. Even 30/30 is lighter enough (by roughly 60%!) to make this much less of an issue. Hypoxic mix (more He) is even lighter, to the point that the shift of the gas mass is almost inconsequential.
But for most divers where wetsuits are going to be in use, simply due to depth and water temperature at that depth issues (it gets colder as you go deeper), you will likely be on some form of Nitrox. SOME people (Kool-Aid drinkers in particular) might be on 30/30 at depths beyond 100'.
Nitrogen and Oxygen are relatively close in molecular weight; they are "neighbors" on the periodic chart, and both are diatomic as molecules. He is monoatomic, and has a molecular weight of ~4. N2 and O2 have molecular weights of ~28 and ~32, respectively.
So if you have a mix that is made up of 30% Helium, the Helium part weighs only 14% as much as an equivalent amount of N2 would! That's a HUGE difference.
Effectively, 30/30 has a mass of only 41% that of 30% Nitrox!
So if you have 18 lbs of EANx30 in a set of HP120 doubles (about right) if that gas was 30/30 Trimix you'd have 7.5lbs of gas in the tanks! That's a biiiig difference - probably enough of a difference that swimming up your full tanks is not going to be much of an issue, assuming you are weighted properly on the surface.
For higher He content Trimix, the gas is even lighter of course.
So, the entire issue of finding yourself at the bottom with a holed BC and unable to swim up the mass of your gas, assuming you have properly weighted yourself at the surface for your dive, is likely to only be a factor if you are diving a Nitrox (Nitrogen and Oxygen only) mix of some description. And it is precisely under these conditions that you would consider potentially venting some of the "extra", quite-heavy, gas in order to be able to swim up your rig.
If you are diving a Trimix or Heliox gas, it is extremely unlikely that the mass of the gas is a factor in the trouble you find yourself in - which implies that absent being stupid about your weighting in the first place, you should not have a problem with 'Mix in this regard.
As for freezing a reg, this concept (ditching gas as opposed to weight) is a self-rescue option to cover a holed BC where you have no secondary buoyancy option. This implies you're diving wet, as if you're diving DRY you use the drysuit as a BC to get off the bottom.
I doubt you're going to be doing that in water cold enough to freeze a reg on you if you were to vent the gas.
Trimix is much lighter. Even 30/30 is lighter enough (by roughly 60%!) to make this much less of an issue. Hypoxic mix (more He) is even lighter, to the point that the shift of the gas mass is almost inconsequential.
But for most divers where wetsuits are going to be in use, simply due to depth and water temperature at that depth issues (it gets colder as you go deeper), you will likely be on some form of Nitrox. SOME people (Kool-Aid drinkers in particular) might be on 30/30 at depths beyond 100'.
Nitrogen and Oxygen are relatively close in molecular weight; they are "neighbors" on the periodic chart, and both are diatomic as molecules. He is monoatomic, and has a molecular weight of ~4. N2 and O2 have molecular weights of ~28 and ~32, respectively.
So if you have a mix that is made up of 30% Helium, the Helium part weighs only 14% as much as an equivalent amount of N2 would! That's a HUGE difference.
Effectively, 30/30 has a mass of only 41% that of 30% Nitrox!
So if you have 18 lbs of EANx30 in a set of HP120 doubles (about right) if that gas was 30/30 Trimix you'd have 7.5lbs of gas in the tanks! That's a biiiig difference - probably enough of a difference that swimming up your full tanks is not going to be much of an issue, assuming you are weighted properly on the surface.
For higher He content Trimix, the gas is even lighter of course.
So, the entire issue of finding yourself at the bottom with a holed BC and unable to swim up the mass of your gas, assuming you have properly weighted yourself at the surface for your dive, is likely to only be a factor if you are diving a Nitrox (Nitrogen and Oxygen only) mix of some description. And it is precisely under these conditions that you would consider potentially venting some of the "extra", quite-heavy, gas in order to be able to swim up your rig.
If you are diving a Trimix or Heliox gas, it is extremely unlikely that the mass of the gas is a factor in the trouble you find yourself in - which implies that absent being stupid about your weighting in the first place, you should not have a problem with 'Mix in this regard.
As for freezing a reg, this concept (ditching gas as opposed to weight) is a self-rescue option to cover a holed BC where you have no secondary buoyancy option. This implies you're diving wet, as if you're diving DRY you use the drysuit as a BC to get off the bottom.
I doubt you're going to be doing that in water cold enough to freeze a reg on you if you were to vent the gas.
