How long do air fills remain useable?

[Token]

I bought a couple of used tanks a while back, got them filled in the spring of 2016 expecting to use them in the summer...and they stayed in my closet til now. [work schedule issues and etc,] Finally I have weekends off again and will have a few opportunities to dive over the summer and while I'll be getting these tanks scoped and hydroed and refilled this week [doing a cleanup lake dive June 2] I find myself wondering whether the tanks would be useable in any way as they are? How long will a tank fill stay 'good'? Weeks? Months?

My purpose in buying these tanks was to have them filled and ready to go if a dive opportunity popped up during the dive season here [June to October, basically], rather than having to organize a tank rental and return. Bad strategy?

 

[scrane]

Should be good. Take a hit and see how it tastes.

 

[tomfcrist]

Assuming it was good quality air to begin with...dive em.

 

[grf88]

If the tanks were dry and the fills were good you will be fine. The Oxygen in the atmosphere has been around for several billion years so a couple extra should not hurt. Some of it will have been recylcled but it is still the same Oxygen.

 

[АлександрД]

I`d read story, as one our diver some years ago had dive, using "air of freedom" - he had take scuba, was filled in soviet times, and go diving.
No problems.
So, for steel cylinders - it could be years....

Two problems could be - rust particles and non tested tanks.
In case of good compressor with air dryer and with good inner condition of tanks - it could be years.

 

[Fibonacci]

Slightly OT... I recall there was a call out by our CSIRO for old SCUBA tanks with fills dating prior to 1970 to be analysed as part of atmospheric research:

Atmospheric scientists believe air contained in disused dive tanks can potentially extend what is already the longest record of greenhouse gases in the Southern Hemisphere.

Their serendipitous finding emerged after a Melbourne recreational diver contacted CSIRO Marine and Atmospheric Research (CMAR) Laboratories at Aspendale offering a very old air sample contained in a long-disused SCUBA compressed air tank.

Funded and managed by the Bureau, the Cape Grim Station detects atmospheric changes as part of a scientific research program jointly supervised by CMAR and the Bureau. Extensive data are collected for studies of sources and sinks of greenhouse and ozone-depleting gases. The data are used in assessments of past and likely future atmospheric composition.

According to the diving diary of the SCUBA tank's owner, Mr J. Allport of Beaumaris, the tank was last filled in 1968 and last used in 1970. A diving service company in Melbourne's CBD filled the tank and it therefore contains ambient air from the city precinct.

Analysis of the air sample using a range of detectors has generated new trace gas data on; propellants, refrigerants and aluminium smelter emissions (HFCS and PFCs), present in the global background atmosphere of 1968, but not widely used in Melbourne at that time.

"If tanks were filled in a clean coastal environment their usefulness in measuring greenhouse gases such as carbon dioxide, methane, nitrous oxide and chloro-flurocarbons (CFCs) is much broader," Dr Fraser said.

Now, the scientists are ready to start a search for SCUBA tanks or other compressed air tanks filled before 1970.

Wonder if anyone volunteered to test-breathe that clean 60's air?

Read more at: https://phys.org/news/2010-03-tank-air-csiro-archive.html#jCp

 

[67macoshark]

I found a pair of 72's at a garage sale a couple of years ago. The owner bought them new in 1968, doubled them up, and had them filled. They sat unused since. There was 1800 psi in them when I got them. I tested the air with my new at the time cootwo, and found 20ppm CO. You hippies really knew how to party!!!

 

[Bob DBF]

My record is somewhere around 7 years. Too many tanks to dive and that particular tank wasn't my favorite.


Bob

 

[Graveyarddiver]

I used an AL 80 with a full tgat was 8 years old, I was in a pinch, and had no issues. Gas tasted fine. Tank is obviously due for a hydro now. I also used a steel Drager deco bottle, with an O2 fill that was roughly 15 years old, again no issues.

 

[Seaweed Doc]

Huh. I've got a tank I was going to scrap (or make into a bell) that I'd guess was last filled after a VIP/Hydro about 2010. Maybe I should keep it around....