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I wonder, what is content of output of zeolite-based pressure swing adsorption oxygen concentrators (both oxygen output, and exhaust output)?

Yes, they can produce 95% oxygen.

But what's the remaining 5%? Is it just argon and other noble gases, or some air contaminants could also be concentrated (like CO2, NO2, CO)?

Any references to quantitative gas analysis results would be extremely useful (wasn't able to find any, probably bad google skills).

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The remaining 5% could in a normal, air-operated concentrator be `anything else' that was present in the air. Looking at this example and explanation, anything that ends up in the outlet stream is what was not absorbed. Then the question remains: does absorption occur equally for all air components (except $O_2$ of course) or does it differ?

I can give you some numbers (see also the presentation I referenced above), but the absorption depends strongly on the type of zeolite. For example this $AgA$ zeolite has a 1.63:1 $Ar$ selectivity and a 5:1 $N_2$ selectivity with respect to $O_2$. Whereas the $LiAgX$ zeolite has only 1.1:1 $Ar$ selectivity.

In this article they mention that they can get 95% $O_2$ with the remaining 5% being almost completely $Ar$. However, they use a contaminant free inlet mixture of $O_2$, $N_2$ and $Ar$.

The most interesting for you is probably this article. They study how $H_2O$ and $CO_2$ affect the operation of a zeolite oxygen concentrator. What they show is that there is not going to be any $CO_2$ in the outlet stream, but instead $CO_2$ adsorbes so strongly on the zeolite that it will degrade its overall efficiency.

In summary, to answer your question, species like $CO_2$ and $NO_2$ will deactivate your zeolite, but this is due to excessive adsorption so this means that the outlet flow will only contain $O_2$ and $Ar$ and sometimes a small amount of $N_2$.

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That is very informative, but normal air has at least 380ppm of CO2, but as far as I see these oxygen concentrators typically have 10 years lifetime - so it doesn't seems that co2 damages them. –  BarsMonster Mar 21 '13 at 8:09
    
That can very well be. I think (but don't know for sure) that commercial oxygen concentrators will be overdesigned such that they can lose a lot of activity over the years while remaining on spec. That is at least how many household appliances operate. –  Michiel Mar 21 '13 at 9:05
    
Heads-up: Finally I've got oxygen concentrator & CO2 monitor. It appeared, that there was only 35ppm of CO2 in generated oxygen (background level ~450ppm) –  BarsMonster Jun 1 '13 at 11:57
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