Close to 100% nitrogen in an old tank?

[KevinNM]

You’d also need something else going on in the Al tank, as formation of aluminum oxide will normally seal off the raw aluminum from the air and stop the reaction. That’s why Al tanks are durable even when banged around.

 

[DandyDon]

I've been following this thread without comments wondering If the second-hand story in the original post could be true & factual, or if there had been a misunderstanding in the retelling. @Kurtis Clark I am sorry for the loss of your friend but hope if you can get to the source to learn what actually happened.

Now this second-hand story has me wondering more...

He said that he had a regular customer/friend pick up a nitrox fill. Friend doesn't check O2 percent at pick up. Does check it a few days later, and it's a few percentage points lower than it's supposed to be. Customer comes back to complain to the owner. Owner apologizes, no idea what happened, but won't happen again. Next tank, it happens again. Third tank, owner fills himself, promises customer THIS one is good. Few days later, customer checks the tank, O2 percent is low. Returns to the shop. They remove the valve and find a considerable algae growth of some kind in the tank.
They think the algae was oxidizing the o2.

Algae normally produce oxygen in daylight but do consume some in dark or when dying. I have to wonder if a few points on an oxygen tester could really show up after a few days.

 

[AfterDark]

I've been following this thread without comments wondering If the second-hand story in the original post could be true & factual, or if there had been a misunderstanding in the retelling. @Kurtis Clark I am sorry for the loss of your friend but hope if you can get to the source to learn what actually happened.

Now this second-hand story has me wondering more...

Algae normally produce oxygen in daylight but do consume some in dark or when dying. I have to wonder if a few points on an oxygen tester could really show up after a few days.

Fresh water lake / pond fish kills due to O2 depletion caused by algae is common.

 

[DandyDon]

Fresh water lake / pond fish kills due to O2 depletion caused by algae is common.

Yes, cloudy weather and overpopulation can be the source of the "consume some in dark or when dying" that I mentioned.

From: Fish kill - Wikipedia

A few species of algae produce toxins, but most fish kills due to algae bloom are a result of decreased oxygen levels. When the algae die, decomposition uses oxygen in the water that would be available to fish

 

[CT-Rich]

You could wipe out all the O2 with a contaminating bacteria. That seems like it would be really hard to do. Argon or helium would seem like the most likely culprits or it was a N2 tank meant for filling paintball guns. People forget what they have in the garage sometimes

 

[Seaweed Doc]

I've been following this thread without comments wondering If the second-hand story in the original post could be true & factual, or if there had been a misunderstanding in the retelling. @Kurtis Clark I am sorry for the loss of your friend but hope if you can get to the source to learn what actually happened.

Now this second-hand story has me wondering more...

Algae normally produce oxygen in daylight but do consume some in dark or when dying. I have to wonder if a few points on an oxygen tester could really show up after a few days.

You definitely need light for algal growth. Once it's there, though, it could suck up a lot of oxygen in the dark.

But what allowed it to grow in the first place? No light in a sealed tank. Even bacteria need a food source. Maybe there were hydrocarbons blowing past the filter that fed a bacterial overgrowth?

 

[Jonn]

If there was some sort of living ecology inside the tank, that would be deeply weird and wrong aside from the fatality! There’s nothing to eat in there and if there was the gas would stink very badly anyway; you would know. If the tank inner wall corroded enough to consume all the oxygen, it would have ruptured first. The corrosion would not have been perfectly distributed across the area, it would be mostly in one spot and eaten through the thickness. It was filled with N2 (or argon?) from the start. I fill my tires with my tanks all the time, it’s very plausible that a car enthusiast might get a nitrogen fill for that purpose and mix things up. Not saying it happened, but plausible. Remember kids: carefully label everything that isn’t air!

 

[CuriousRambler]

First, I'm sorry for your loss Kurtis.

Several comments about nitrogen for filling paintball guns through this thread. Just as a point of clarification, nitrogen isn't generally used for paintball guns. The industry generically refers to higher end air sources as "nitrogen tanks," but in reality most, if not all are filled with regular compressed air. Entry level stuff all uses CO2, but the higher end equipment relies on compressed air so it can be reliably pressure regulated for consistency (i.e. accuracy), where CO2 stored in tanks as a liquid has a tendency to get drawn into regulators and freeze o-rings.

Most paintball "nitrogen" fill stations are compressed air cascades serviced by the local welding outfit for smaller shops/fields, or a regular scuba compressor for folks who do enough volume. I'm not saying nobody uses actual nitrogen, but I've never knowingly come across anyone who's actually using legitimate dry nitrogen for paintball purposes. That said, very very few people in the industry call it "compressed air," and the norm is to refer to it as "nitrogen," albeit erroneously. I'd bet >95% of the "nitrogen" used in the paintball industry is actually scuba quality breathing air.

Source: used to own a 4500psi compressed air cascade station for my team, traveled regionally for tournaments in the PNW, and worked at a couple places with larger fill stations.

 

[rjack321]

. I'd bet >95% of the "nitrogen" used in the paintball industry is actually scuba quality breathing air.

I agree with you in concept but not sure I believe its actually suitable for breathing. Painball places seem to rarely change their filters. But its probably not acutely toxic just very wet (ie too much moisture)

 

[CuriousRambler]

I agree with you in concept but not sure I believe its actually suitable for breathing. Painball places seem to rarely change their filters. But its probably not acutely toxic just very wet (ie too much moisture)

You're almost positively correct, and I definitely wouldn't encourage anyone to go around getting their dive tanks filled by the local sports store's paintball crew haha. I guess I could've been more accurate and said "air compressed with scuba quality equipment." I highly doubt any shops are replacing filters, much less monitoring for quality.