Bad Air??

[pescador775]

About 20 years ago, I calculated the amount of rust to render a tank hypoxic but I don't remember the amount. Yes, it is indirectly time dependent, it directly depends on the physical weight of the iron oxide. Time factor will vary with the corrosive nature of the contaminant. Salt water, maybe 6 mos.

Scuba tanks do not normally become contaminated, spontaneously, while in storage. Don't worry about it. However, if in spite of this you still worry crack the valve and smell the air. Tilt the tank and listen for rust particles. Get a VIP.

SSI diver. In spite of what netdoc says, steel tanks do occassionally get rust due to incomplete filtration. There are other causes as well. That explains the VIP program.

 

[AquaTec]

I read something just a week ago about air quality in tanks, and i have been trying to finmd it to quote it here and on another thread. but can't.
I will go from my bad memory

Air in a tank is breathable forever as long as there are no contaminates inside the tank upon filling it, in the air that is used, or any introduced after containment.

Air stored in a cylinder does go stale, and they had a bunch of good reasons for it. but it is still breathable.

as for rust in a tank. you are talking to a guy who tumbled steel 72's for many years as a youth, there can be an amazing amount of rust in a tank, i have seen them rust through. meaning once they where tumbeled clean there where actualy holes in the tank. however before that they held pressure.

the most common way a tank gets moisture is because it is blead down to zero, even a few pounds of air will keep moisture out.
the other is from compressors, mostly on boats, and of course bad filtratrion.

This is the whole reason the vip progam started, it used to be that you could just bring any old tank and get it filled.
In Hawaii you didn't go to a dive shop for a fill you went to a fill station, where all the shops and hotels brought their tanks. so we saw them all.