How long can air sit in a tank?

[tbone1004]

cue why i'm lucky I get air for free, but yeah, all the shops charge it, sucks really bad.

 

[flots am]

I bought 2 nice clean al80's, one had 700psi, the other was 3k.. I'm not sure when it was filled, but the last vis was August 2011, so at the most, it's been in there for 4 months.. Will the air go stale, or bad after awhile?
thanks

It's good until it isn't. How's that for non-helpful?

Seriously, in an aluminum tank, the air will be good until it leaks out, or unless the tank is contaminated.

In a steel tank, the air will be good until it leaks out, or the tank is contaminated or unless there's water in the tank. Water creates rust which is bad, but also uses up some of the oxygen.

This is one of those times where the only real answer is that If you have to ask the question, the answer is that "It needs to be checked."

You should be able to take it in to a shop, have them drain it look inside and refill it for not much more than the cost of a fill. They don't need to do a VIP or cleaning or anything else, just look inside and make sure it's not all crapped up, rusty or badly contaminated.

FWIW, it doesn't matter if they're clean on the outside, you want to be sure they're clean on the inside where the air is.

flots.

 

[Chugwhump]

I bought 2 nice clean al80's, one had 700psi, the other was 3k.. I'm not sure when it was filled, but the last vis was August 2011, so at the most, it's been in there for 4 months.. Will the air go stale, or bad after awhile?
thanks
mike b

You are most probably fine with that teenie AL 80 (Barbie tank).
You could drop by a dive shop and analyze the O2 %, assuming that you do not have other acess to an O2 sensor.

I have left some of my cylinders (both steel and Al) sitting in the garage with gas in them for over a year and so far, so good, when I have used them.
A few caveats......
I am in SoFla.
I get great gas, from great shops, with great compressors, in my well maintained tanks.
I cannot see where you are with this tank geographically, but :idhitit:

Chug
Likes 149's at 4200.

 

[Tigerman]

I bought 2 nice clean al80's, one had 700psi, the other was 3k.. I'm not sure when it was filled, but the last vis was August 2011, so at the most, it's been in there for 4 months.. Will the air go stale, or bad after awhile?
thanks
mike b

If the air is at most 4 months old the LAST thing Id worry about would be it being stale.
It being filled at a source you dont know, with what can be air or other gas that you dont know, with possible contaminants of which you dont know what is...
Id just drain them and have them refilled..

 

[Hatul]

The only scenario I can think of where otherwise good air will go bad is if there is moisture in the tank that is causing corrosion of the metal, decreasing the O2 in the tank over time.

If you're worried about this you can always use your Nitrox oxygen meter (Analox O2EII or equiv) to measure percent O2.

 

[Tigerman]

And if it was filled from a bad compressor and is high on CO? That would concern me more than what happens if the tank has been standing in my halway for 4 months (Which it will while the local sites is frozen over)..

 

[grf88]

If it was good when it went into the tank and the O2 level shows that it has not reacted with the tank then you are good to go. After all how old do you think the air was when it went into the tank.

 

[ajduplessis]

Do the normal smell/taste test, if all smells well it should be fine. If in Doubt refill, air is cheap and not worth taking the risk. Clean air/ cylinders should be fine for at least a couple of months.

 

[mathauck0814]

where are you getting $4 air fills? luckily I have compressor access, but the shops here charge $8 for an al80 and $12 for anything bigger for air...

Brutal man, routinely $4-5 in both places where we live and dive... and that's when they bother even charging for it at all! It does make it hard for me to justify the fill station I want to build to my wife though since it's unlikely to ever "pay off"

 

[faster7581]

im in florida, fills are only $4.. while i was at the shop yesterday filling the other tank, I saw 4 nice tanks they had for sale there too... after thinking about it, i could use a 3rd tank.. i'm going to pick up one of those today, and for $4, i'll just get my other one dumped and filled... I dont know who or what was used to fill it, so for piece of mind, $4 is worth it...thanks for the replies
mike b