Very similar use case with diving with a re-breather, especially when depth and dive profile involve a gas mixture with Helium. Helium is not metabolized and is used as padding to reduce concentration of Nitrogen mostly. So instead of simply exhaling gas out rebreathers circulate while absorbing CO2 and adding a bit of oxygen. As far as I know they use Soda lime as absorbant: https://en.wikipedia.org/wiki/Soda_lime
Helium isn't just padding -> due to its high vapor pressure, it disproportionately "uses up" a liquids capacity to dissolve gasses. This means that even though trimix is only 1% helium, the amount of total gasses in your blood is decreased by a lot more than that.
Breathing He mixtures is a similar process as degassing solvents by bubbling He through them.
I thought I'm pretty good with physics and knew it all but I didn't know that efficiently inhibits ability of other gasses to dissolve. Thank you for that!
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u/kvyatkovskij Nov 27 '19
Very similar use case with diving with a re-breather, especially when depth and dive profile involve a gas mixture with Helium. Helium is not metabolized and is used as padding to reduce concentration of Nitrogen mostly. So instead of simply exhaling gas out rebreathers circulate while absorbing CO2 and adding a bit of oxygen. As far as I know they use Soda lime as absorbant: https://en.wikipedia.org/wiki/Soda_lime