Air fills in Nitrox Marked Tanks

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Manatee Diver

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elan

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Ok, another dumb question:

Say I've got a HP100 with ~2,000 PSI of EAN32 in it... am I wrong to just ask a shop to top it off with air? I understand the resulting mix would fall a bit below 28% (of course I'd analyze/verify and mark it on the contents tag), which is fine with me. I don't need nitrox on my next couple dives, my closest dive shop doesn't do nitrox fills... just wondering if I'll look like a big dummy with this request. I don't need 28%, I'd be fine with standard air.

Or am I just best off draining the tank and asking for an air fill? Does it really matter?

An easy answer is: draining no, you do not need to drain it, you can just top it off. More complex answer is: I understood this is not a shop that you normally fill our tanks with Nitrox. And this shop only does air. There is a very high probability that the compressor they use does not produce air compatible with O2 fills and as such might contaminate your tank with hydrocarbons (i.e. oil mist). Which means you need to clean the tank before you fill your tank again with nitrox at a shop that uses partial pressure blending. This is a rule (it's actually more blanket like "any nitrox fills") that was taught in all nitrox classes I ever took. If you ignore it you might get into breathing CO in your mix as the process of filling the tank will pp and and "some mix at some psi " is draining the tank fully then fill it with O2 first. At this stage oil and O2 mix really "well". You might not get an explosion but CO in your mix is very likely.

If your regular shop fills from a bank then you are OK but you will need to remove the o2 clean mark from the vis label so you are not confused later.
 

tursiops

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If you ignore it you might get into breathing CO in your mix as the process of filling the tank will pp and and "some mix at 1000 psi " is draining the tank then fill it with O2 first. At this stage oil and O2 mix really "well". You might not get an explosion but CO in your mix is very likely.
I do not understand the logic nor the chemistry of your statement.
 

Wookie

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An easy answer is: draining no, you do not need to drain it, you can just top it off. More complex answer is: I understood this is not a shop that you normally fill our tanks with Nitrox. And this shop only does air. There is a very high probability that the compressor they use does not produce air compatible with O2 fills and as such might contaminate your tank with hydrocarbons (i.e. oil mist). Which means you need to clean the tank before you fill your tank again with nitrox at a shop that uses partial pressure blending. This is a rule (it's actually more blanket like "any nitrox fills") that was taught in all nitrox classes I ever took. If you ignore it you might get into breathing CO in your mix as the process of filling the tank will pp and and "some mix at some psi " is draining the tank fully then fill it with O2 first. At this stage oil and O2 mix really "well". You might not get an explosion but CO in your mix is very likely.

If your regular shop fills from a bank then you are OK but you will need to remove the o2 clean mark from the vis label so you are not confused later.
Where are you people making crap up from and then peddling it as gospel?

Repeat after me:
Oxygen is not flammable
Total hydrocarbon concentration limit for oxygen compatible air is 25 PPM.
Total hydrocarbon limit for breathing air is 25 PPM.
Total hydrocarbon limit for nitrox? That’s right, 25 PPM.

Oil is different.

Most (like 99.9%) of compressors in the first world do not use hydrocarbon oil to lubricate the compressor. The overwhelming majority of compressor owners are using synthetic diesther or triesther oils. If you’re getting your air from a shop using mineral oil in their compressor, you need to find a new shop post-haste.

251E17E8-AAA4-4DE2-BA4D-E17AEA74A668.png
 

Tracy

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An easy answer is: draining no, you do not need to drain it, you can just top it off. More complex answer is: I understood this is not a shop that you normally fill our tanks with Nitrox. And this shop only does air. There is a very high probability that the compressor they use does not produce air compatible with O2 fills and as such might contaminate your tank with hydrocarbons (i.e. oil mist). Which means you need to clean the tank before you fill your tank again with nitrox at a shop that uses partial pressure blending. This is a rule (it's actually more blanket like "any nitrox fills") that was taught in all nitrox classes I ever took. If you ignore it you might get into breathing CO in your mix as the process of filling the tank will pp and and "some mix at some psi " is draining the tank fully then fill it with O2 first. At this stage oil and O2 mix really "well". You might not get an explosion but CO in your mix is very likely.

If your regular shop fills from a bank then you are OK but you will need to remove the o2 clean mark from the vis label so you are not confused later.
I honestly want to know, where did you come up with that?
Seriously, did you make it up? If someone told you that, slap them.

You will be hard pressed to find a commercial compressor making non o2 clean air for more than a week. Any normally operating machine will make oxygen compatible air, just because they don't test for it doesn't mean it isn't making it.
A machine with mechanical issues will produce dirty air, it will also fail in short order.
I work on a lot of compressors, I always take air samples with no filtration installed. Testing after filtration tells me nothing about the separators and coalescors. All it tests is the filtration.
Commerical compressors in good operating condition will pass for oxygen compatible with zero filtration installed.

An MCH6, or bauer Jr, no, but those aren't commercial units.
 

AfterDark

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NItrox tanks need to be oxygen cleaned as O2 is flammable it's not just about filling the tanks and going, the tanks have to be certified to hold the enriched air, your lds should be telling you this in addition to giving you a hard time over fills.

Now wait if O2 is flammable then why can't I light/ignite the O2 coming out of my cutting torch? It will not light/ignite until I add propane to the mix. Not much will burn without O2 but I haven't been able to light/ignite it up yet. Hope I'm not getting bad O2!
 
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