I visited a gas filling plant in Germany last year (Riessner) They produce all oxygen to the same standard into the same tank. So there is no difference!
You have a dive shop that fills it for you, which is a plus. Dive shops usually need a transfill adapter, which you can get in a welding shop for around 20 Euro. In German.
I don't know what system you are about to buy, but go for a big cylinder.
Diving oxygen specification is more strict regarding water content then aviation oxygen. Freezing in scuba equipment is more likely in cold water due to fact that whole assembly is immersed in cold media and pressure drop can cause sub-zero conditions in regulator's 1st stage. IMO using diving oxygen for flying is 100% safe. The most important things when handling the oxygen are to use oxygen compatible materials and lubricants in all components of the system and to maintain low flow rate during transfilling.
If diving oxygen would contain more oxygen, then why aren't the steel bottles corroding on the inside?
Divers usually carry oxygen in small (6 to 11 liters) aluminium tanks due to better bouyancy characteristics of these tanks and the fact that pure oxygen is used only for the last phase of decompression at depths shallower than 6 meters. Only when stationary decompression habitats are used, oxygen is filled to large steel tanks submerged and attached to habitat. And of course when stored on surface, large steel tanks are used.
Diving oxygen specification is more strict regarding water content then aviation oxygen
The question, however, is whether the actual gas is any different.
My info, which admittedly is only one data point, is that all modern oxygen is the same - give or take what original atmospheric gases might be left in the last < 0.1% of impurities.
I have also never read anything suggesting different production methods for the different-marketed oxygen grades.
And I agree re steel cylinders. You can't have them corroding. I was told by BOC they inspect them for rust only every X years so it doesn't seem to be a problem.
Actual gas is the same. Cylinders are visualy inspected, sand-cleaned and hydrostaticaly pressure tested periodicaly, period depending on material.
Thanks a lot for the insights. It confirmed what I was already thinking: Same gas, different marketing and paperwork, and a different price.
I'm going to order the MH CFFC-048 cylinder (fiber wrapped) with 4 constant flow regulators...
I would personally go for the pulse regulator from Mountain High. I started out with the constant flow regulator, but the pulse regulator will save you a lot of oxygen on the same trip and it much more comfortable as the dry air is not constantly flowing in your nose. And I would also get a good oxygen saturation meter.
I agree re the O2D2, very much, but it does depend on the hassle involved in getting a refill.
If you have easy refills, then the constant flow system, with oxymiser cannulas, is actually really good. The 48 cu ft cylinder will probably do 2 people at FL150 all the way down to Crete and back.
With the O2D2 it would be 1/3 used.
The other advantage of the O2D2 is that if you forget to shut off the valve after a flight (easily done) the leakage is insignificant and you will get away with it - other than perhaps flat AA batteries in the O2D2. With constant flow, you are out of the game by the next day.
--"Diving oxygen specification is more strict regarding water content then aviation oxygen"
it should be, if at all, quite the contrary - image you get a rapid decompression in a high flying plane which puts you in seconds from +23 to -60°C. I think in aviation it is even more important not to have any water content in the oxygen. But Peter and others have already demonstrated that these are OWT (old wives tales) ... all the same stuff ...
it should be, if at all, quite the contrary - image you get a rapid decompression in a high flying plane which puts you in seconds from +23 to -60°C.
If you are in a pressurised aircraft, you wouldn't need oxygen. Isn't that the point of pressurisation?
Not sure about the going from +23 to -60 in seconds (admittedly I have no experience in trying it!). If the aircraft is pressurised at +23°C, air at 23°C will be pushed / sucked out of the aircraft until the pressure equalises. Factor in maybe a 10 °C change in temperature as a consequence of adiabatic expansion, and what you are left with is gas at ambient pressure at 13°C. Which would then cool via conduction across the fuselage temperature gradient, gradually.
I'd put fairly sizeable money on this +23 to -60°C change NOT happening in seconds, unless of course the cockpit windows get blown out!