Remember that there is absolutely NO DIFFERENCE between medical, welding and aviators oxygen. It is all produced by liquefaction and comes out of the same pipe. Once the use is defined, the price and availability changes by the liability incurred by the provider. Welding O2 is the cheapest, because of the fact that it is not "intended" for human consumption. "Aviators Breathing Oxygen" is often delivered at slightly higher pressure (2,200 psi vs. 1,800 or 2,000 psi) but costs more, as the "primary" cylinder must be emptied and purged by the supplier prior to refilling. A "Lot Number" must also be recorded for each primary cylinder refill. This does not apply to individual use cylinders like the ones we use in our gliders. Medical Oxygen costs the most (liability again), usually requires a Doctor's prescription and is rarely available for general non-medical use. Carrying a simple transfiller adapter can sometimes get you a refill at a welding shop, but the simplest method is to just carry a spare cylinder and transfiller so you can refill your glider cylinder. You should also have the specifications on your glider cylinder and delivery system, meaning you should know how long your supply will last at your maximum expected altitude and available pressure. For example, a 415 liter (14.7 cu ft) cylinder at 2216 psi will deliver 12.3 man/hours of oxygen at 15,000 ft MSL using a Mountain High EDS delivery system. The same system will provide approximately half the duration if it only has 1,100 psi. If you are using a standard straight cannula or face mask with constant flow, you only have 4.0 hours at 15,000 ft MSL. Know your equipment!

BTW, oxygen refills are available at Moriarty, NM through Sundance Aviation..