Posted by CalAbDiver on August 20, 2001 at 13:20:38:
In Reply to: Re: so none of you dummasses has heard of mixing helium with air? posted by Jeff B on August 20, 2001 at 10:57:12:
it just doesnt make a lot of sense to me when instead of several O2/He/N2 variations one simple 50/50 mix of ordinary air with helium would dilute the O2 enought to completely avoid O2 tox and would delute the N2 enough to make a 300 fsw dive the simple equivalent of a 132 fsw air dive.
air at 21/0/79 diluted 50% with He to 10.5/50/39.5 gives an EAD of 132 for a 300 fsw dive so the USN tables for a 130 fsw dive could be used for decompression, and with EAN42 and EAN84 as deco & travel mixes you could begin deco at 90 sfw as needed and switch to the EAN84 or 80%O2 at 30 fsw for your last 3 deco stops at 30,20,&10 fsw.
you could switch off the EAN42 used as travel mix anywhere between 33 fsw and 90 fsw depending on the dive plan and the bottom time requirement.