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Aviation Oxygen (merged)

I’m planning to buy a MH O2D2/CFFC-048 setup for my round-the world flight. I fly a lot in the US, so I’ll probably go with the 540 thread.

Has anyone got a recent source for an adapter for this thread, to allow filling at scuba shops (or better suggestions for what adaptor(s) I should carry)? Going round-the-world I imagine that scuba shops might be my best source of refills along the way!

KPJC and Kent, UK

This may also be of interest. In practice scuba shops can be hard to locate, especially as only the more specialised carry oxygen.

Shoreham EGKA, United Kingdom

I’ve recently purchased an O2 system (Aerox) and refilling it is proving a bit of a challenge even here in the US. On one occasion away from base the local Medevac guys helped me out and at my base the only shop that does it has run out of O2, delivery next Tuesday….

BUT, what I’ve learned in the process is not to use medical or scuba O2 because of its higher moisture content. I had a longish conversation with the Medevac people and they of course have both medical and aviation O2 and were totally adamant to use aviation O2 only for the flight crew.

That said, at least Aerox have an adaptor what they call for ‘off-airport’ refills which may or may not be what you’re looking for. Just check their website.

There is close to zero water in any oxygen you get in cylinders. The cryogenic process, used for all commercial O2 in the past few decades, produces a ~99.9% pure oxygen, and water would corrode the cylinders and other stuff. It’s an old myth; see further back up the thread.

On Katamarino’s question, MH sell quite a few fittings.

If a refill hose is required, I used Sub Aqua Products in the UK; details here.

Shoreham EGKA, United Kingdom

Whatever. I think I’ll choose to believe the Medevac people. They do this all day, every day and had different bottles for their aviation and medical O2. I doubt they do that for fun.

Somewhere online there’s a write-up of a chap who decided to take a Turbulent (open top) above 20k feet. As I recall the water in his Oxygen froze and he became hypoxic.


I bet you anything it was condensation in his tubing that froze.

It is not possible (using the modern cryogenic process) to manufacture o2 with water in it, and if you added it, it would be liquid at the pressure. It would be useless.

Google on steam tables and see what water looks like at a few k psi…

The only way to add water would be to add it into the low pressure gas. It would be non trivial; you would have to evaporate the water – probably by boiling it, or with forced air, like in humidifiers, and mix the vapour with the oxygen. The water vapour will be trying to condense (room temp, ambient pressure) unless you keep the % below a certain figure, and you would need drains in the system. Just like in a humidifier actually. I am not saying that water is not being mixed with oxygen in a medical or some other scenario but it sure as hell isn’t coming like that out of the high pressure cylinder.

And then you get huge corrosion issues in the cylinders, especially the steel ones used for wholesale gas distribution.

Shoreham EGKA, United Kingdom

…scuba O2 because of its higher moisture content

You’re completely wrong on this (or whoever told you that is speaking total nonsense and doesn’t know anything about scuba and/or oxygen).

LDZA LDVA, Croatia

172driver wrote:

Whatever. I think I’ll choose to believe the Medevac people. They do this all day, every day and had different bottles for their aviation and medical O2. I doubt they do that for fun.

I could well be for administrative reasons. Different certifications/standards are involved and even though the same O2 could meet both standard, it may not come with “double papers”.

ESKC (Uppsala/Sundbro), Sweden

There are those who care about papers and pay through the nose (if they can, availability is poor), and those who don’t and happily fly on welding Oxygen.

Biggin Hill
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