Nitrox Blending Rental of Air Cyclinders

[v101]

I have my own compressor and have been pumping my own AIR for about 8 months now, and have been reading Vance Harlow's Oxygen hackers handbook. Great book very helpful.
I have been considering building a nitrox stick and pumping my own nitrox.

Wanted to ask others how they have fared getting oxygen from their local gas suppliers, and what type you have got from them?
Are you getting aviators oxygen? or medical grade oxygen?
did you get a script from your doc?
And are you leasing the bottles from the gas supplier? and if so what are they charging you for this?

 

[BRT]

Welding O2. Had a pilot stop by 2 days ago to transfill his O2 bottle. He seemed happy to disconnect the welding regulator and hook up his hose. I buy the bottles. I have one big one that I use primarily for nitrox and several smaller ones I use primarily for cutting and brazing.

 

[JohnnyC]

Welding O2. Had a pilot stop by 2 days ago to transfill his O2 bottle. He seemed happy to disconnect the welding regulator and hook up his hose. I buy the bottles. I have one big one that I use primarily for nitrox and several smaller ones I use primarily for cutting and brazing.

NO NO NO NO NO EFF NO!!!!

Welding gas is NOT clean like med grade or Aviator grade. Breathing welding O2 under pressure is extremely dangerous. It is NOT clean breathing gas, and blending with it is an accident waiting to happen.

 

[tomfcrist]

How did you come to that conclusion Johnny? Folks have used industrial(welding) O2 and helium for blending diving gasses for as long as those gasses have been around. The reality is that when the gas company fills industrial O2....it comes from the same tank as the medical and aviators grades come from.

 

[lucca brassi]

it is funny but industrial oxygen is cleaner than medicine have take several certificates from our suppliers ( Messer | Plini za )

point is that welding (quality welding is much more complex than breathing with only 21 % oxygen in air )

 

[JohnnyC]

I have seen trace hydrocarbons in more than one welding gas supply. I'll see if my friend still has the quality reports. His shop was contracted out for some aerospace stuff. Their oxygen bottles were contaminated. It ended up costing them a bunch of money. If I can get them I'll post them here.

The Praxair and Arigas shops that I used to get welding bottles from had an entirely different O2 supply for med and av gas.

Again, why risk putting contaminated O2 into a tank you're going to be breathing from, whether partial pressure or through a compressor, potentially causing flashing and carbon monoxide build up that can overwhelm a filter stack introducing CO into a tank. There's a reason that there are purity standards when it comes to medical O2 and Aviator O2 for a reason. The fact that some people have gotten by makes no difference. 60 fpm ascents used to be recommended too, and a bunch of people never had a problem....still not a great idea.

 

[tomfcrist]

Medical and industrial O2 have the exact same standards. Known as type b.
Aviators merely has a tighter standard concerning water content. Known as type a

Both are suitable for diving applications. You can look it up yourself in the NOAA diving manual amongst other places.

 

[JohnnyC]

The difference is due to the chain of custody of the tanks. Welding gas is simply refilled without regard to ensuring that it is free of contaminants. Medical grade and Aviation grade have specific standards dealing with contaminants in the tanks and their required total evacuation between fills. There is no guarantee when purchasing a tank of industrial gas. When purchasing medical grade or aviation grade you are guaranteed a standard of cleanliness without other trace elements.

If you're willing to risk it, be my guest, but there's a reason blending courses stated the need to use USP Medical or Aviator gas.

If it's all the same, why does Praxair specify so many different possible grades?

Oxygen |What is Oxygen?

Grade A is 99% O2, Grade E is aviator grade, and it has more than simple water content specifications.

Here's a good guide to O2 written by a PhD at Michigan.

Oxygen Labels

The bottom line is you are free to use what you want, but recommendations are made for valid reasons. Disregard as desired.

 

[tomfcrist]

I own my cylinders. They don't need to be evacuated, because nothing goes in except pure O2 or helium from my supplier.

The reality that even the least pure commercially available O2 or helium is still has fewer contaminants than 90% of the fill stations out there. The only thing that would remotely be a concern would be CO, and that is assuming some sort of backwash into a cylinder when being used in a welding capacity...which is improbable at worst, impossible in my application.
Scare people all you want, but some of the worlds most complex and dangerous diving has been done for many years on industrial grade gas and likely will continue to be until we figure out a way to grow gills.

 

[JohnnyC]

Regulations and standards exist for reasons. Which clearly leaves you in the enviable position of recommending others disregard those regulations.