Question - Where do you get oxygen cylinders filled? (2025)

J-Vo:

The large green "T" cylinders are filled by gas supply companies. It works much like propane from the supermarket, where you purchase the tank, then the gas supplier swaps it out for you when empty so you're only paying for the gas and maybe some service fees.

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Most large volume dive shops use dewars of liquid oxygen. But the same process applies. A commercial gas supplier swaps it out with a new one when it’s empty.

Be aware that in many places, you won't be able to get "medical" grade O2 without a prescription. There's plenty of threads on here discussing what, if any, differences there are between Medical, Aviators, and Welding O2.

The common wisdom seems to be that they're all filled from the same source, in the same way, but medical and ABO are tested and come with a certification, so it's the same purity regardless. What you get may depend on if you're talking personal use or reselling.

Capt Jim Wyatt:

Get aviators O2 not medical.

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Thanks. That was the missing piece. I called the gas supply company I’ve used for welding gas and they do sell aviators grade oxygen.

coolfilmaker:

Thanks. That was the missing piece. I called the gas supply company I’ve used for welding gas and they do sell aviators grade oxygen.

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Are you renting/leasing those welding bottles or are they "owned" by you? Every supplier is a bit unique in how they deal with refills vs exchanges vs owned vs leased cylinders. Prescriptions for medical, availability of ABO etc. It's hard to generalize across suppliers since they all seem to make up their own rules and policies.

As others said, with most larger gas suppliers you typically would pay a lease fee for the bottle. You can then you simply swap them out with a fresh bottle when it's empty rather than owning your T bottles of oxygen. You just pay for the gas and any fees/taxes for any new bottles you get.

It is far easier this way. The gas supplier doesnt have to keep track of your personally owned cylinders and they handle all hydros and valve replacement on the cylinders themselves.

Go to any of your local gas suppliers, open an account. Order whatever you need. It's typically hit or miss in my experience if they will sell you medical grade. There are no issues with aviator's grade and some larger gas suppliers might even sell what they call a "diving grade" which is a bit of a scam/way for them to just charge you more money but once they hear the word "diving" some will get a little gun shy about selling you gas.

The gas supplier can generally deliver cylinders (for an extra charge) to your location if you are commercially zoned and/or have a loading dock. I just pick up and swap cylinders with my pickup truck every few months when I need more gas.

Regarding welding grade: Some of use are pretty happy using industrial oxygen for personal use but if you are selling gas to any clients then it should absolutely be certified as breathing grade. I'm not going to get into this argument here as it's been rehashed about a million times but almost all industrial oxygen is filled using the same process. It's the paper trail that follows the bottle that is important and the procedures they use (e.g. if they pull a vacuum on the cylinder)

rjack321:

Are you renting/leasing those welding bottles or are they "owned" by you? Every supplier is a bit unique in how they deal with refills vs exchanges vs owned vs leased cylinders. Prescriptions for medical, availability of ABO etc. It's hard to generalize across suppliers since they all seem to make up their own rules and policies.

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I found tanks on Craigslist without a name on the neck ring. That’s the hard part. Most of the oxygen tank listings have a business’s name on the neck ring and/or significant rust. They said they can convert helium tanks to oxygen service, and those are much easier to find in good condition. That’s how I got my welding tanks.

TravisD:

Be aware that in many places, you won't be able to get "medical" grade O2

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Florida law allows anyone with a Oxy Handler's cert to buy medical grade Oxy. Like Jim said, aviator's grade is just fine. You didn't hear it from me, but it all comes from the same big tanks.