[Mark Chase]

For what its worth

25 @ 60 on 18/45

5m/min ascent to...

1 @ 39 gas switch to 32%
2 @ 18
4 @ 15
5 @ 12
6 @ 9 gas switch to 80%
25 @6

Decoplanner 20/80GF

5 min ascent to the surface added by me

But that’s not the question. The question was is it worth putting He in the deco mix. The answer is Yes if you believe current thinking. At first gas switch depth using 32% you would have a PP of Nitrogen of 1.8. When you switch to 32% your PPn would be 3.4 this is a bad thing. So to prevent this you would swap to 32/35 to give a PPn of 1.65. Thus continuing the reduction in the Nitrogen and reducing the He as well.

This is claimed to greatly improve the decompression at a sub clinical level and to me it makes sense. If you put the He into the profile it increases the deco but the divers actually running these gases appear to be ignoring the He.

Bobs profile has a switch to 50 % at 21m with a PPn of 1.15. The switch to 50% puts him on a PPn of 1.55. The shock to the system is far less and therefore the profile looks better than a swap deeper to 32%.

If it weren’t for my personal preference of bail out gas I would have preferred to run 50% for deco. As it was I have been doing a lot of research into adding He to my 32% and if I had stayed OC that’s the option I would have gone for on my longer deep dives (60+).

Food for thought and I certainly don’t have enough medical knowledge to adequately argue the case but on a layman level it seems pretty obvious that hiking the PPn is a bad thing.

ATB

Mark Chase