How long can air sit in a tank?

[cbrich]

http://airtesting.com/wp-content/uploads/2012/06/aircode-specifications-Apr-08.pdf

This explains the different requirements between the different type of air test. This particular places tells you if you pass or fail, then they give you table of what your air sample tested at, and how it compares to the requirements.

 

[Deep South Divers]

That pdf file shows a chart of what that particular company's "standard" is. Never once does the terms "grade D" or "grade E" appear on the document.

If an organization (dive shop, fire department, government, etc.) adheres to a standard (and they don't always have to), then the common standards are set by one of the following organizations within the United States: ANSI, CGA, OSHA, or NFPA. All of those organizations require "grade E" if the gas is stored in a bottle, cylinder, or tank.

The confusion comes from the fact that OSHA didn't yet have a name for "grade E" when they mandated it's use... So they called it "grade D with less humidity." Essentially, that's "grade E."

"Grade D" air is only a standard for breathing compressors that do not store or bottle the gas... In other words, a surface-supplied compressor... Not a compressor that can fill a SCUBA OR SCBA tank.

 

[cbrich]

That pdf file shows a chart of what that particular company's "standard" is. Never once does the terms "grade D" or "grade E" appear on the document.

Check the line for Limiting Characteristics. If you have a problem with how they do air analysis because it does not meet your satisfaction, then why don't you call them up at 512-263-2101, and you give them a scolding. This company gets air samples from all over the country, not just Texas. This just a short list of what they can do.

How about you put together a table of all the requirements, don't just speak Grade, D, E, modified E, blah, blah. That stuff is meaningless, I want to see this.

For each Industry standard list their requirements.

Grade (whatever you call it)
Oxygen content
Water (ppm)
oil (mg/m3)
Particulate (mg/m3)
Odor
Carbon Monoxide (ppm)
Carbon Dioxide (ppm)
Total VHC (ppm)
Nitrogen Dioxide (ppm)
Nitric Oxide (ppm)
Sulfur Dioxide (ppm)
Halogenated Solvents (ppm)
and anything else that is left off.

I am curious to see what you provide, and how this differs from what TRI Air Testing does.

 

[Shftrdog]

As long as there is no water in the tank you are fine, if you crack open the valve open a little you can smell it. If there is not smell then it is fine, if there is a smell then it is not. You can also taste it when you hook up your regs

 

[grf88]

I picked up an old steel 72 that would appear to have not been used since 1977 which was the date of the last visual. I tested the air and discovered 7ppm CO. Not that I expect anything has happened to the air since it went in the tank but it does suggest that filtration and/or testing was a little different 35 years ago. I now have a good supply of bump gas.

 

[Deep South Divers]

A "scolding?". Why would I do that? These are this companys eir standards, which are pretty consistent with what I have seen from other testers.

My point about it not mentioning "grade D" or "grade E" is that labs dont generally test to a certain level... They simply test whats in the gas, report the findings, and classify it.

...Which supports my point, not the point of the guy that cited the source.

If you want to know what is in certain grades of breathing gas, please use Google. They are a world-recognized ANSI/CGA standard, and are easy to find.

FWIW, there are many gasses that are odorless, including CO, CO2, and carbon monoxide. The smell test is not an effective test against all toxins - in fact, its not an effective test against MOST toxins.

 

[bj139]

I recently bought a used AL80. The VIP had expired in 1992. It had 2800 psi in it. It tasted fine on the surface. I used it in a dive and it was OK. It is getting a hydro and VIP now. The dive shop personnel said the air may have lost O2. They also said the tank may not pass hydro because of it's age. Is age a reason for failed hydros? They have a sign in the shop saying not to fill any tanks older than 1990. I suspect this is because of the bad aluminum alloy phased out in 1988.

 

[Deep South Divers]

To answer your question: No, age has no factor in a failed hydrostatic test. Either the tank passes the test or it doesn't. If in doubt, have it hydroed and VIPed... By another shop.

Luxfer issued a rebate plan for a small number of tanks manufactured out of an aluminium alloy that was unusual at the time. The affected tanks would have been manufactured from 1987 to 1988. The "new" alloy at the time was supposed to be more corrosion resistant. However, there was later a theory that, over long periods of time, the alloy would slowly lose structural integrity, and the "old" alloy was reused, and continues to this day.

In short, if you have a tank manufactured during this time (and it is very unlikely), then you could return the tank to Luxfer for a $50 rebate towards the purchase of a new Luxfer tank.

The bottom line is... Whatever the alloy is that your tanks are made of, if they pass hydro, use them.

Many shops took this as an excuse to "ban" all pre-1990's scuba tanks, probably in an effort to encourage sales. It's little more than a sales tactic. Only a limited run of one year of one manufacturer has ever been questioned, and even then not recalled.

FWIW, Luxfer claims to have seen no regular catastrophic failures of any of their tanks of any alloy... And no other manufacturer has ever used the questioned alloy.

If you have any doubt... Call Luxfer. They are at Luxfer: Setting The Standard Worldwide

 

[teknitroxdiver]

I recently bought a used AL80. The VIP had expired in 1992. It had 2800 psi in it. It tasted fine on the surface. I used it in a dive and it was OK. It is getting a hydro and VIP now. The dive shop personnel said the air may have lost O2. They also said the tank may not pass hydro because of it's age. Is age a reason for failed hydros? They have a sign in the shop saying not to fill any tanks older than 1990. I suspect this is because of the bad aluminum alloy phased out in 1988.

Where would the oxygen have gone?

Sent via teletype

 

[spectrum]

I regularly dive air that is stored over the winter making it 6 months+old.

The only small possibility of concern here is that you do not know the history of who has been filling and how they have been cared for.

Pete