"Expiry date" on filled tanks

[Kaos]

I've been diving 15 years, 400+ dives, and will most likely be flamed for this stupid question, but I prefer having my ego bruised other than something much worse. I vaguely remember back when I go cerfified something about "Don't use air from a tank that hasn't been used in a while". But now I search on the Web and don't find anything that answers this question. Is it BS that I immagined?

If not how long is "a while"? The reason I'm asking is because I have a al. 80 cu feet that I VIPed in April and plan to use in a couple of weeks. I store it in a dry, dark place where the surrounding temperature varied from 65 to 79 F (18 to 26 C) over the last four months.

Even with the flames, I'm very curious to read the answers.

 

[Drew Sailbum]

is probably with steel tanks, particularly if there has been some water intrusion into the tank prior to the last fill. Steel tanks can then begin to rust on the inside, and the rusting process will reduce the oxygen concentration selectively.

Is it a real problem? Probably not a major drop in FO2, but you can hedge against that by draining the tank and taking it in for a fill. Not really needed for an aluminum tank, IMHO.

 

[livestodive]

on Wed I dove 2 al 100's that were filled last August. They were fine, I dove them to empty them and then have hydro and vip's done. I wanted fresh hydros done because I am selling them to a friend. He actually likes diving those heavy suckers!

 

[scubacowboy]

All I've heard is that the air can taste kinda stale after sitting for awhile, but IMO refilling with air cost only a few bucs so why bother using old air.

 

[FredT]

1. Sniff it and see if it smells "funky".
2. If you have an O2 meter get a FO2 reading on it. Anything below 20.8% is not a good sign.


If the air was good going in, the air is good 3 to 5 years later. If the air was wet or otherwise bad going in storing it overnight is too long!

FT

 

[JJ1]

Even good air can have minute nasties growing in it.........

As a firefighter and hazmat tech the general policy (and OSHA standard) is to have the air replaced at least once every 4 months in our air packs.....

Knowing that......... that's what I do with my scuba stuff too (not that they get to sit for 4 months without use )