SparticleBrane
Contributor
There should only have been one response to this thread:
"Nothing."
...and that should have been it.
"Nothing."
...and that should have been it.
Changing a tank from nitrox back to air?
- Thread starter demarest652
- Start date
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Scared Silly
Contributor
I would do some of everything above.
As said air is nitrox just 21%. I would drain the cylinder down and fill it. At that point I would analyze the contents to ensure that it was 21%. Then go dive it.
Some shops may have a problem with any stickers that say Nitrox or O2 clean. But that is another can of worms.
As said air is nitrox just 21%. I would drain the cylinder down and fill it. At that point I would analyze the contents to ensure that it was 21%. Then go dive it.
Some shops may have a problem with any stickers that say Nitrox or O2 clean. But that is another can of worms.
Personally, I'd top it off with air, analyse the mix, dive it and repeat the process. Eventually you get a very close approximation of air, but you still get the benefit of a little extra O2 along the way. All them plants work hard to make O2, it is a shame to waste it.
In the past I'd fill with 32% for shallower dives, breath the tanks down to 1/3rd, then top with o2 compatible air and get a 25% mix that worked well for deeper dives in the 130-150' range. Then dump the tanks and start over. Nitrox does not have to be just 30%, 32% or 36%.
In the past I'd fill with 32% for shallower dives, breath the tanks down to 1/3rd, then top with o2 compatible air and get a 25% mix that worked well for deeper dives in the 130-150' range. Then dump the tanks and start over. Nitrox does not have to be just 30%, 32% or 36%.
Do what I do, have it filled with 21% nitrox. 
Given the nature of the question, I'm willing to bet he does not have an EANx card, and is probably buying a tank used from someone or somewhere.
The consensious is - fill it, test it and dive.
The problem is not what should be done, it is what will the shop filling it require. Right or wrong, they will present you only with options they are willing to do.
If it were me, what they don't know, won't help. Peel the sticker off, drop it off for fillling. Test the mix before the next dive or just stay shallow <75' and forget it.
The problem is not what should be done, it is what will the shop filling it require. Right or wrong, they will present you only with options they are willing to do.
If it were me, what they don't know, won't help. Peel the sticker off, drop it off for fillling. Test the mix before the next dive or just stay shallow <75' and forget it.
elan
Contributor
You do not have to do anything but analyze the mix after refilling and make sure the final mix is compatible with your diving profile. The other question is - are you going to use this tank for NITROX later ? if the answer is no than you do not have to worry, if the answer is yes then 2 things are possible if the filling shop fills it on the filling station used for filling nitrox and they use the corresponding air (it was called Safe Air above) then you do not do anything after. If it's just a regular station then you would want to have it cleaned after.
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