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Imho the key point your missing is balanced risk
Originally Posted by JonG
The risk of poor decision making due to narcosis and the risk of retained c02 due to high density gas, far outweighing the manageable risk of helium decompression which can be mitigated with conservative decompression choices.
When we planned a 140m dive I was lucky enough to talk to some people at Comex and their attitude 15 years ago was Nitrogen had no place in a deep diving gas.
Have no fear I am too much of a fuckwit above water never mind under it to be twatting about with mind bending ENDs.
In the 90s mix was hard to come by so mostly we were on air with long durations at 50 and shorter excursions to 60-70, the lack of paranoia and sense of impending doom on a mix at depth now is much more enjoyable.
It was more of an academic interest in the change of opinion from the 90s to now. Does anyone know what caused the negative mindset back then? It was very much the norm to get off it quickly and have in mind that a helium bend was hard to treat, but that may have been due to the fact that we weren't properly decompressing the squishy grey bits properly so neuros were more common perhaps.
I never bent on mix, just air but with a tea bag for a ticker it could have been either anyway.
If there was a bias of safety towards either end of the scale it would all be marginal gains and balancing pros and cons.
The current trust in high fraction trimix seems a little misplaced imho in the absence of more testing to understand the implications of a cocktail in comparison with heliox.