When planning a dive with a single deco bottle, when do you decide to plan on 50% vs. O2, and why? Assume standard gases and depths in the 100-130ft (30-40m) range.
So far I've heard two reasons for the choice:
- Change from bottom gas: If you're using 32% or 30/30, it doesn't make much sense to use 50% for deco.
- Fast vs. slow tissues: If you are doing shallower dives and going into deco, you are doing longer dives. Therefore you'll wind up with more slow tissue saturation and more time on O2 at 20ft is better for that.
My current thinking for each depth is something like:
Depth.........Bottom gas...Deco gas
100 ft...............32%.......100%
110 ft....30/30 or 25/25.......100%
120 ft....25/25 or 21/35........50%
130 ft....25/25 or 21/35........50%
If the bottom gas is the reason, where would you draw the line? E.g. for a 110 ft dive on 30/30 would you use 100%, but the same dive on 25/25 use 50%? Or 120ft dive on 25/25 use 100% but same dive on 21/35 use 50%?
So far I've heard two reasons for the choice:
- Change from bottom gas: If you're using 32% or 30/30, it doesn't make much sense to use 50% for deco.
- Fast vs. slow tissues: If you are doing shallower dives and going into deco, you are doing longer dives. Therefore you'll wind up with more slow tissue saturation and more time on O2 at 20ft is better for that.
My current thinking for each depth is something like:
Depth.........Bottom gas...Deco gas
100 ft...............32%.......100%
110 ft....30/30 or 25/25.......100%
120 ft....25/25 or 21/35........50%
130 ft....25/25 or 21/35........50%
If the bottom gas is the reason, where would you draw the line? E.g. for a 110 ft dive on 30/30 would you use 100%, but the same dive on 25/25 use 50%? Or 120ft dive on 25/25 use 100% but same dive on 21/35 use 50%?