Depends on the concentrator, but note that most concentrators max out a bit over 8k. Also, multiuser concentrators are rare. You sometimes see two-person ones and those aren't very common. I've never seen more than two users.
I got an Inogen G5 that has 6 O2 settings. I configured it with the minimum battery (since it will plugged in) and made not attempt to mount it. It is a single user system.
Since my use was aimed at optimizing pilot performance at the 8-10k altitudes where I normally fly, single user is okay. My wife/co-pilot mostly sleeps.
With that said, I put a T fitting in the tubing and feed two cannulas (I recommend the standard canulas over the soft ones that most regular users prefer. The standard canulas will not crimp so easily when routed around headphones). I use a clamp to make it a single user system.
I’m 67. Without O2, at anything above 8k flying for over 2 hours, I get sleepy. At 10k I start getting down to 90% saturation according to an oximeter. Hooking up to the concentrator as a single user, I’ve never set it over the ‘3’ setting and am easily able to stay in the 95% level up to 10k.
At this point I’ll just stay that I haven’t consistently recorded statistics so the recollections here are subject to qualitative and quantitative errors. YMMV and all that.
With both of us breathing from the single unit, we both stay above 90% up to 14K’. And that’s at the 5 or 6 level settings. We haven’t tried higher.
My sense is that with 2 people breathing through a T fitting, we are getting more efficient utilization of the O2 potentially produced. I don’t know if that’s actually true.
Is this cost effective? I don’t know. But I learned that I’m unwilling to keep my O2 tank filled and/or unwilling to use it as supplemental O2 below the legally required altitudes because of the hassle involved east of the big river. My sense is that out west O2 fill-ups are more commonly available. Yes, a home O2 tank fill-up system would be cost effective but I just didn’t go that route. So far, the concentrator is a simple ‘switch on when desired’ system with no frequent maintenance required. Very handy, compact, easy to use. The units are somewhat expensive. How long I can go before major service and such I just don’t know yet. We’ve been traveling less than usual due to you know what.
The most important point is that I feel the need to use O2 outside of the legal requirement. The concentrator makes that easy to do, so I end up doing it.
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