cold water/sealed regs

[ghosch]

Since you've provided an opening ;D

It is true that the air you breath from a rebreather is warmer than OC. The chemical reaction warms it, as well as your body as the same air passes through your lungs many times. Rebreathing the air also moistens it leading to greater comfort and hydration. The difference is noticable after a long dive in cold water (of course, never having dove in EXTREME cold, I guess I wouldn't know).

With a rebreather traditional free flows become virtually non-existant (I suppose it is still theoretically possible) because all the regulators are doing is occasionally (or continuously in the case of SCR) injecting miniscule amounts of gas.

There are other situations on a rebreather which can lead to an unregulated flow of gas, but they aren't caused by freezing!