CaveSloth
Contributor
Think about how many minutes the gas will last you at different depths. 1 cf per minute is a conservative estimate of surface breathing rate. That means 2 cf per minute at 33 ft, 3 cf / min at 66 ft, 4 cf / min at 99 ft.
2 85 cf steel tanks doubled together will give you roughly about 42.5 minutes of air at 100 ft. If you are practicing the rule of thirds, that means that you need to turn your dive at around 14 minutes if you are diving double 85s.
With double 133 tanks, you get about 66 minutes of air or turning the dive at 22 minutes instead.
2 85 cf steel tanks doubled together will give you roughly about 42.5 minutes of air at 100 ft. If you are practicing the rule of thirds, that means that you need to turn your dive at around 14 minutes if you are diving double 85s.
With double 133 tanks, you get about 66 minutes of air or turning the dive at 22 minutes instead.