Medical vs. Aviation Grade O2

[Kunundrum]

Hey guys,

Quick question I have seen some shops using Aviation grade O2, my LDS use Medical grade O2. other than cost, is there a significant advantage/disadvantage to using one vs. the other. For Nitrox ?

 

[fire_diver]

Use welding oxygen. It's all the exact same thing, and comes from the same supply. It's also much cheaper.

 

[sardiverdan]

I found this little note ....from Aviators Breathing Oxygen... details of composition, FAA regulations, properties and controls.
There are four kinds of oxygen that are merchandised or sold to users; Aviation, Medical, Welding and Research. There is a ongoing controversy if there is any difference between the different types. Oxygen gas is produced from the boiling off of liquid oxygen. It would appear that the oxygen is therefore the same. Where we obtain oxygen, all the different types of oxygen are supplied from the same manifold system. Then someone says that medical oxygen has more moisture in it. That is partly true. The oxygen going to a hospital bed is plain oxygen that comes from liquid oxygen. At the bed location, there is a unit on the wall that adds moisture. At this moment we now have medical oxygen. If the oxygen is in a pressure vessel or in a manifold system (like inside a hospital) then it is regular oxygen. The cost of medical or welding oxygen is normally much less than the oxygen you get at an airport.

Also of interest, we have been told by the suppliers of welding oxygen, the purity level required for welding and cutting purposes is more critical than for breathing.

The bottom line about the different types of oxygen is in the insurance liability of the oxygen supplier. The gas is the same but the insurance liability is different.

 

[Akimbo]

I have been in at least 20 industrial gas plants in the US and Europe over a 40 year period. All of them used Cryogenic Air separation for Oxygen and Nitrogen. The process compresses and cools atmospheric air. Each gas including Oxygen, Nitrogen, and the trace gasses have different boiling points and are separated as liquids into its components in a distillation column. They use high purity stainless steel diaphragm multi-stage compressors with a simple inlet filter for particulates — more to extend the life of the machinery than anything else.

There is a process called Vacuum Pressure Swing Adsorption, but I have never seen it used. As you can imagine, cryogenic separation produces tremendous purity. Most importantly, the vast majority of the remaining "impurities" are light gasses that are metabolically inert.

I have seen huge manifolds filling both industrial and medical gas cylinders at the same time. The only difference is the medical cylinders had chrome valves and better paint jobs — oh yeah, and cost more. The contracts I have seen with large gas consumers like diving companies specify 99.95% pure, though they often tell a walk-in buyer 99.5% since they like to sell the higher margin medical gas.

I have only seen industrial grade Oxygen used in the commercial diving industry and the Military for O2 makeup, treatment gas, and Oxygen-fed metal cutting torches. Most hospitals get their bulk Oxygen as a liquid from the same cryogenic process except it is not heated back up to a gaseous state and compressed in cylinders.

Cryogenic oxygen plant - Wikipedia, the free encyclopedia

 

[vjanelle]

Medical O2 flasks are sometimes vacuumed out before filling, and there's a longer paper trail.

 

[coldsmoke]

Aviators 02 for me is only about $4 more per cylinder - so I buy that. Helium on the other hand is quite different. Industrial He runs around $85 and high purity He is over $200. I use industrial.

Hunter

 

[fire_diver]

The cost of each gas, and the for the different grades of gas vary wildly from shop to shop. When I started looking for an O2 cylinder, I was shocked at the differences in both tank leases and refill costs.

 

[NAM001]

Hey guys,

Quick question I have seen some shops using Aviation grade O2, my LDS use Medical grade O2. other than cost, is there a significant advantage/disadvantage to using one vs. the other. For Nitrox ?

a good reference is the oxygen hacker from airspeed press.

the air grade is super dry air to prevent o2 line freezing from moisture in the gas on planes that have o2 lines on the skin of the plane. > 80% o2

med o2 is i think > 80% o2 and when filled the bottle is vacumm empty then filled to insure no contaminates.

welding o2 is 99.x% o2

all the gas comes out of the same storage tank. the filler may do some filtering on some of the lines for some of the fills.

the reall difference is the price.

med o2 $$$$$ needs a perscription to get
avation o2 $$ probably have to get at an airport
welding o2 - well 20 bucks for a tank refill from a gas supplier

i have no problem using welding o2.

i will soon make my own o2 from a concentrator and pump it into a 2200psi o2 tank

 

[Karl_H]

There some pretty comprehensive answers so far but I thought I'd add a simpler one!

In basic terms Aviation O2 has a lower moisture content than Medical O2 to prevent ice forming at high altitude/low temperatures. Otherwise they are the same basic product, Aviation O2 is more expensive and will cause more dehydration than medical O2, therefore I'd avoid Aviation grade O2 for diving as it has no obvious benefit other than giving you drier air - I would put this as as a major disadvantage for any dives in which you are using hyperoxic mixes for either bottom gas or accelerated deco.

As discussed the difference between Welding O2 and Medical O2 is only the tank in which it is supplied, Medical oxygen tanks are cleaned before every fill, Welding oxygen tanks are cleaned a lot less frequently - as O2 is pretty cheap I'd avoid using the Welding grade stuff as there's not really much cost saving - Helium on the other hand is a lot more expensive for the breathing grade......

So to sum-up the actual post question, Aviation grade is more expensive than Medical grade oxygen and is actually less appropriate for diving, particularly open circuit - stick with Medical!

Karl

 

[DA Aquamaster]

As noted above the difference is in the bottle and the contaminants that may be in it. If you own your own bottles, then the evacuation of the cylinder is not really an issue. If you rent, or more importantly, exchange the cylinders, then it could be.

As noted above aviator O2 is required to be dry by the FAA, but I doubt it is in fact any drier than medical or industrial O2 - same source, same process, etc.

The major practical difference is that O2 suppliers will sell you aviator O2 no matter who you are, while in many states medical O2 requires a prescription.