Marine Scientist and Master Instructor
- Reaction score
- U.S. East Coast
- # of dives
- 2500 - 4999
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Nothing special needed. 40% is about as safe as air, regardless of what CGA and other handwringers say.
No need to worry about moisture - the gas in the tank contains only traces of water vapor so there nothing to condense if you dont go all the way empty.
If you rapidly drain a tank all the way empty, yes you can get condensation inside from vapor in ambient air.I used to think the exact same thing and after rather rapidly draining a steel tank in order to get a VIP, there was a lot of water in the tank.
I always assume that even if there was cooling and condensation (from rapid release of the presumably dry air) that subsequent filling would rapidly result in the re-evaporation of the previously condensed water. The rust in some steel tanks has somewhat convinced me that this "assumption" may not be valid either.
If you rapidly drain a tank all the way empty, yes you can get condensation inside from vapor in ambient air.
I let the tank warm up to room temp before draining all the way or immediately put it on a hot air dryer (quicker).
Scuba air should have a very low dew point much lower than you would get from the adiabatic cooling of the tank. Maybe in warm locations this is not too important but in cold water locations it can result in serious problems.Well, it was my conclusion that the water was in the tank the instant it was opened up, there was no introduction of ambient air - or not enough to allow measurable water. Drain the steel tanks slowly