Yours isn`t an "easy to answer" question, and that`s why you haven`t got any answer yet. The reason is simple: from that data, a competitor may gather very useful information.
My suggestion is to search for that information within the largest gases producers in the world, who are the following:
- Praxair, from the U.S. www.praxair.com
- AGA, from Sweden. www.aga.com
- Air Liquide, from France. www.airliquide.com
- British Oxygen, from England. www.boc.com
From my personal experience, I also suggest you not to post any question on their site. Questions asking for technical information posted on sites are very seldom answered. Instead, get the telephones numbers of their U.S. offices and get in contact directly with them by phone. Be prepared to be passed over from one person to another until you reach the "guy who knows".
Let me know how you came out. Good luck.
Giovanni S. Crisi
Sao Paulo - Brazil

P.S. I feel quite honored for having been of service, even if a small one, to anyone less than the Battelle Memorial Institute.