You need ~0.2 Bar of oxygen partial pressure. The purpose of Trimix/Heliox is to keep oxygen partial pressure under 1 Bar while also reducing nitrogen to prevent narcosis. You can't breathe the 200m mix at sea level pressure.
> You can't breathe the 200m mix at sea level pressure.
What makes you think you can’t (other than it being hypoxic)? You most certainly can breath Heliox, in fact, it has been used medically[0] for almost 100 years, far longer than used for commercial diving.
Heliox doesn’t denote a specific concentration of helium and oxygen; even just within diving the mix varies depending on the depth it is to be used at.
Also, the oxygen partial pressure you need to stay under is 1.6 Bar for oxygen toxicity. Huge difference between 1.0 and 1.6, depending on oxygen percentage, the difference could be a >50% reduction in MOD.
jsjohnst|7 years ago
What makes you think you can’t (other than it being hypoxic)? You most certainly can breath Heliox, in fact, it has been used medically[0] for almost 100 years, far longer than used for commercial diving.
[0] https://en.m.wikipedia.org/wiki/Heliox
johncolanduoni|7 years ago
jsjohnst|7 years ago
ConceptJunkie|7 years ago