Rebreather World - View Single Post - How to dive deep

jhaaja · 21st April 2006, 10:11

Quote: (Originally Posted by Mark Chase)

Obviously a lot of work went into this article and your efforts are to be applauded. However I would have a serious rethink about using air as a bailout gas for a trimix dive. Doing a 70m dive on something like 18/45 diluent and getting a problem so bad that bailout is required at depth I would not like to be hitting the narcosis of air and I don't fancy the DCI risk of the nitrogen spike either.

Personally I would have something like 21/35 as bailout for a straightforward clear ascent dive and i would use 18/45 for an overhead penetration dive or back to shot dive.

On a 70m dive we would have 80% staged on the deco station and a drop tank on the boat. As a result we would carry a 10 of bottom mix and a 10 of intermediate deco ranging from 32/30 up to 50% depending on the deco commitment. 50% is a good gas but often you will exceeded the capacity of the 10ltr on the deep mix unless you can switch deeper than 21m.

No deco station? then i would carry a third gas or operate team bailout.

ATB

Mark Chase

I would second this. It sounds a really stupid thing to change to air from a good trimix. The narcosis will hit you bad and you are allready excited because of the shit flying around because of the bail-out.

I like to have nearly the same amount of helium in my deep bail-out mix.

JH

21st April 2006, 10:11	#5 (permalink)
jhaaja Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Mar 2005 Location: Finland Posts: 885	Re: How to dive deep (50m+) Quote: (Originally Posted by Mark Chase) Obviously a lot of work went into this article and your efforts are to be applauded. However I would have a serious rethink about using air as a bailout gas for a trimix dive. Doing a 70m dive on something like 18/45 diluent and getting a problem so bad that bailout is required at depth I would not like to be hitting the narcosis of air and I don't fancy the DCI risk of the nitrogen spike either. Personally I would have something like 21/35 as bailout for a straightforward clear ascent dive and i would use 18/45 for an overhead penetration dive or back to shot dive. On a 70m dive we would have 80% staged on the deco station and a drop tank on the boat. As a result we would carry a 10 of bottom mix and a 10 of intermediate deco ranging from 32/30 up to 50% depending on the deco commitment. 50% is a good gas but often you will exceeded the capacity of the 10ltr on the deep mix unless you can switch deeper than 21m. No deco station? then i would carry a third gas or operate team bailout. ATB Mark Chase I would second this. It sounds a really stupid thing to change to air from a good trimix. The narcosis will hit you bad and you are allready excited because of the shit flying around because of the bail-out. I like to have nearly the same amount of helium in my deep bail-out mix. JH
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