Is my air still good after 8 months?

[Shipwreckscanada]

I filled my 119 cubic foot steel cylinders in August 2013, I'm going to make my first dive since that fill next April 2014, is the air still good to use?

 

[PSUSCUBA1313]

I'd test the air before diving it. If there was any moisture in the tank, it could have rust in it which would have eaten up the oxygen. Just test it as you would for nitrox.

 

[letterboy]

you need to roll it around to mix it again.

 

[ccx2]

you need to roll it around to mix it again.

Wouldnt shaking it be better than rolling it?

 

[crosshairs]

if the tanks are clean, I'm sure its fine......if you have any doubts of the tanks condition, you can analyze the tanks just to be sure...if you do not have an analyzer the dive shop who does your fills should be happy to analyze them for you at no charge

 

[Kharon]

Hey! DOn't listen to those guys. Rolling or shaking won't help. The air in those tanks is now permanently toxic. I will dispose of them at no cost to you and even pay shipping since I'm such a good samaritan.

Honestly, all joking aside, I doubt that you have anything to worry about. My LDS said that it's a good idea to store steels on their side and once a month rotate them an eighth turn so any moisture doesn't sit in one place. Other than that they said not to worry.

As far as rust using up the O2 - it would take a heck of a lot of rust. My PK Chem equations are too far gone to recall but I seriously doubt that there would be any significant reduction in O2 from rust that didn't also destroy the integrity of the tank. I could be wrong but I'm not going to tax my brain to dig out the equations and do the math. I'm retired and so is my brain. It works but only to keep me safe submerged -LOL.

 

[letterboy]

Wouldnt shaking it be better than rolling it?

only if you stand on it while rolling, the increased pressure from your body wieght creates the proper pressure to convert from oxygen, nitrogen and miscellaneous gases to breathable air.

 

[DivemasterDennis]

It should be fine. Never store any tank totally empty, best to leave about 200 psi in them at least. So if nothing new got in since your filled the tank, nothing bad should come out, no less than a year later.
DivemasterDennis

 

[rx7diver]

My LDS said that it's a good idea to store steels on their side and once a month rotate them an eighth turn so any moisture doesn't sit in one place.

Kharon,

I learned that steels should be stored *standing*, but not full (say, containing 200-500 psig), long term. The bottom of a steel is much thicker than the sides and so can tolerate a bit more rusting/pitting than the sides.

Safe Diving,

rx7diver

 

[TMHeimer]

I've used 6 month old air a number of times with no problems (didn't even think of the rust thing, assuming that the yearly visual would catch that). You could always cup your hands around the valve, release some air and smell it. I would think 8 months would be OK as well. I have heard some people say no good after as little as 4 months but they are in the minority.