I know that you have to maintain them monthly and change the sieve beds, but how many years are the units good for and do they have an certification expiration date ?
Whatever you do stay away from Inogen. They are living on their name now and I have personally known of several of their newer mini models going down very quickly. The GE ZEN-O-lite and GE ZEN-O are way ahead of them in almost every way. No certification expiration date and the units last many years with just sieve tube replacements (DIY easy and cheap), filter care and yearly or two yearly inspections by a dealer which is also cheap.
I know that you have to maintain them monthly and change the sieve beds, but how many years are the units good for and do they have an certification expiration date ?
Whatever you do stay away from Inogen. They are living on their name now and I have personally known of several of their newer mini models going down very quickly. The GE ZEN-O-lite and GE ZEN-O are way ahead of them in almost every way. No certification expiration date and the units last many years with just sieve tube replacements (DIY easy and cheap), filter care and yearly or two yearly inspections by a dealer which is also cheap.