re: Oxygen problems
The three Elektron units on board the space station are the last of their kind. The company that manufactured them has gone out of business, and the engineer who almost single-handedly made the final adjustments of flight units died several years ago. Reportedly he retained some "trade secret" about the final adjustments of the devices -- and it died with him.
It's amazing...and it shows how difficul it is to commercialize such devices, only used in one place....in space.
Raoul