Interesting. Maybe I got confused because I remember watching Simon Mitchell’s talk[1] about the hydrogen dives with Richard Harris. He mentioned that the Comex Hydra tests revealed hydrogen was significantly cold to breathe.
If I’m not mistaken, hydrogen has a lower heat capacity than helium. So how come helium doesn’t feel cold to dive? Could it also have to do with the actual percentages?
Mitchell mentions that for their 245m dive they’re using 4% O2, 91% H and 5% N2. Could it be that most average trimix doesn’t incur a temp penalty because when we’re diving 30/70 it just doesn’t have that much of an affect?