Helium prices are already high outside the US, yet no one has produced a closed-circuit system with acceptable safety. No matter what kind of controls and alarms they build in it's too easy to end up without enough oxygen in the loop. A friend of a friend died here in the northeast Pacific not long ago because he just forgot to turn on the valve, and didn't realize what happened before he passed out.
In the long run I expect we'll end up with more semi-closed systems. They're a little less efficient but inherently safer. Something like this http://www.halcyon.net/?q=node/44 could probably be mass produced at a reasonable price (expensive now due to custom manufacturing).
In the long run I expect we'll end up with more semi-closed systems. They're a little less efficient but inherently safer. Something like this http://www.halcyon.net/?q=node/44 could probably be mass produced at a reasonable price (expensive now due to custom manufacturing).