Air fills in Nitrox Marked Tanks

[SpecialTest]

Depends on what your planned MOD is going to be.

Sometimes if I have 100 bar worth of 40% I get it topped up with air rather than have a new fill of 40%

My planned depth is going to be well below the MOD for 28%. ~35ft vs 132ft. My underwater time is going to be short enough that no real reason to drive further to get nitrox fills. Hence why I just want to put air in my tank. I'm just wondering if I can be lazy and take it in without emptying the tank. Or if I should expect the dive shop to insist on draining the tank before filling with air.

 

[grf88]

Topping off a Nitrox tank with air is a common practice. If the tank is usually filled by partial pressure you need to know if the air is suitable for partial pressure filling to avoid compromising its O2 clean status . If it is normally filled from banked Nitrox it is not really an issue..

 

[Divin'Papaw]

The Nitrox wraps are stupid and really should have no place in scuba today. Any tank could have ANYTHING IN IT! Every tank should be marked with mix and, if desired, MOD, initials, date, etc. But AT LEAST the Mix should be on every tank. I have always refused to put wraps on my tanks. If a shop didn't like it, I just filled them with air, or ideally, got gas elsewhere. I mark all of my tanks with the mix ... 21, 36, 32, etc, etc. Every tank. With the prevalence of nitrox and trimix, that is how we should be handling it. Wraps on tanks are just dumb.

 

[stiebs]

.. am I wrong to just ask a shop to top it off with air?

Pretty standard procedure. Just analyse it, throw a sticker on it, and don't exceed the MOD.

 

[Searcaigh]

I'm just wondering if I can be lazy and take it in without emptying the tank. Or if I should expect the dive shop to insist on draining the tank before filling with air.

Just ask them to top it up with air, then if not using it immediately analyse it the next day.

You can easily calculate roughly what mix you might have by checking the pressure later once it has cooled down.

 

[SpecialTest]

Pretty standard procedure. Just analyse it, throw a sticker on it, and don't exceed the MOD.

As a relative newb, I was doubting myself after my most recent nitrox fill experience.

 

[AfterDark]

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?

Well 28% is good to 130FSW last time I checked so anything above that is good to go.

 

[rhwestfall]

My only stickered tank was done because it was black (for some visibility).

As to topping off, we frequently do "ghetto mix" fills just to use them. Analyze, label, and use for proper MOD....

YMMV

 

[Jay Adams]

I'm new-ish to nitrox diving (certified earlier this year)...

Local dive shop gives me grief when I want air put in a tank with a nitrox wrap, or if I want nitrox in a tank without a nitrox wrap. I always verify the contents and mark/label what the blend is along with MOD, yet it's still a battle with the shop. Am I doing something wrong? Seems silly to "require" a nitrox wrap on nitrox fills, and then simultaneously want none of that if you put air in it. Am I supposed to have dedicated tanks (or remove the wraps and re-install, which sounds downright silly) for this?

Seems pretty logical to me to simply verify the contents, label it accordingly, and then go with that...

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.

 

[Divin'Papaw]

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.

LOL

I guess we’re going there ‘again’!

O2 is flammable, low O2 Nitrox (<40%) is not.