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Nitrox cylinder to use for air?
- Thread starter MrsNic
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Roman_66
Contributor
General rule:
Visual Inspection (VIP) once per year. You should have sticker on tank with date.
Full pressure check (usually also includes VIP) - once per five years. You can see a date on tank itself.
And yes, as people already said : for second hand tank with unknown mix, better drain down to 300 psi at home and last piece in the dive shop.
I personally will do VIP for second hand tank regardless of sticker on it and fill gas from zero.
You never know which king of gas was in.
The whole issue with nitrox labeling is aggravating. I say scrap the stupid green and yellow banding and just put MOD stickers on 'em -- in big numbers that can be seen easily underwater. Even plain old air tanks should get MOD stickers that say 198 ft (60 m). This prevents a couple of dangerous scenarios that keeps rec divers from taking a permanent trip to Davy Jones's locker. (1) I have two nitrox tanks that were both tested and verified. One has EAN32 and the other EAN36. Both tanks look alike. At some later date I plan to dive to 110 ft. max. I grab the wrong tank thinking yeah, that's the one with EAN32. (2) If I'm diving with the wrong mix and provided my buddy had a few less drinks the night before than I did, he can read the MOD and alert me. Knowing the mix by itself is useless unless you know (remember) the MOD for it.
K
KeithG
Guest
simplest (worst) case: Treat it like any tank that is full of something that you have no clue what it is. it could contain almost anything. but not likely, do you feel lucky?
I would take it to your LDS and explain your situation. they will likely err on the side of extreme safety and bleed it out, remove the valve and perform a visual check to ensure there are no hamsters inside. They will then fill it with an appropriate gas mixture for you.
this is a simple, relatively cheap, well known procedure that will give you complete piece of mind as to the current state of the mystery stuff inside the cylinder.
on the other hand: if the tank comes from a reputable source that you trust, just dive it.
I would take it to your LDS and explain your situation. they will likely err on the side of extreme safety and bleed it out, remove the valve and perform a visual check to ensure there are no hamsters inside. They will then fill it with an appropriate gas mixture for you.
this is a simple, relatively cheap, well known procedure that will give you complete piece of mind as to the current state of the mystery stuff inside the cylinder.
on the other hand: if the tank comes from a reputable source that you trust, just dive it.
Mustard Dave
Contributor
See my earlier post (#12) - VIP requirements in the UK (where the OP is from) is every 2 1/2 years.
I agree about the big daft stickers, however, we don't tend to get many of them. I label mine with a piece of tape on the neck with mix, MOD and fill date. On the side of stage bottles, I have a big label with the MOD as well.
I don't see the point in marking air cylinders though - at 60m on a single, you will be in deep do-do with remaining gas, deco and narcosis before oxygen toxicity becomes an issue. Anyone this stupid, to be frank, needs taking out of the gene pool.
And charge you!
Personally I don't think they will - there are loads of cylinders in service with that same sticker. If I took that bottle (with that sticker) to either of the dive shops and tell them the situation, they would either drain it and fill it, or whip the analyser out and test it. If the O2 clean sticker is in date and the visual / hydro is too, they would put whatever I want in it. If the O2 is out of date but the visual / hydro is in date, they would put air in it. If the visual / hydro was out, they wouldn't fill it with anything.
Right....and you can't fix stupid. The labeling on air tanks is for consistency. Regardless of the mix it gets everyone thinking about MOD. If some tanks have MOD and others don't (air) then maybe I don't look at the MOD on the nitrox tank went it could make a difference. It creates confusion which could lead to an accident. Gee...is that an air tank or did the shop forget to put a MOD sticker on my EAN36 tank I'm taking down to 115 ft! The answer of course, is to test the gas. That's fine for experienced and diligent divers. Not so good for others.
DaleC
Contributor
Yes, they do. They don't have the big Nitrox bumper sticker though.
I don't mark the MOD on my air tanks. I know I'm not taking a St72 down to 190'. In this case being focused on MOD's could lead a diver to believe they are safe within those limits while ignoring gas volume and narcosis limits. But why is the shop putting the MOD sticker on for you. Isn't it your job to analyze gas? If you have a tank with no MOD sticker (and you are unfamiliar with it) this simply means you need to reanalyze it.
My personal tanks are by default air, unless I intentionally put EAN in them, then they will have a MIX/MOD sticker.
Having a MOD sticker isn't going to fix stupid. They don't eliminate the need for personal testing and verification. You analyze the gas at the shop and verify the shop puts the correct MOD sticker on your tank. In regards to MOD stickers vs. green/yellow banding the ignoring of gas volume and narcosis limits is a non-sequitur.
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