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There's an article (that reads a lot like an advertisement) at...

    http://ella.netpoint.net/empg/news/ubs.htm

that describes a system for producing de-nitrogenated air nitrox (DNAx)
by filtering an adjustable fraction of Nitrogen from air.  The benefits
of DNAx to the diver are described much as those of EANx.  They also list
benefits to th operator doing the fill, primarily in terms of safety and
simplicity by avoiding high-PPO2 blending.

They make no mention of whether the system filters out any of the less
common gases present in air (mainly argon and CO2).  If it does not, then 
clearly the fraction of those gases in the resultant DNAx mix would be 
higher than in an otherwise similar EANx mix.  The effect would presumably 
increase with the targeted FO2 of the final mix.  So, does anyone know...

  - whether the less common gases are filtered out?

  - how great a fraction of N2 can be removed, and therefore
    what the resultant fractions of argon and CO2 would be if
    in fact this effect occurs?

  - whether there is any significant effect on the diver?

I am mainly wondering about altering decompression penalties with the
argon, and increasing risk of hypercapnia with the CO2.  Worst case, 
if none of the argon and CO2 are removed, I am thinking of fractions
in the neighborhood of 3.6% argon and .13% CO2 in an 80% O2 mix.  That
doesn't seem too horrible, but I figured I'd ask anyway.

Thanks.

- Todd

p.s.  Calculations are based on my assumption that the fraction of
      argon and CO2 would increase linearly with the fraction of the
      oxygen.  Therefore...

      .934 * ( 80 / 20.946 ) = 3.6
      .033 * ( 80 / 20.946 ) = .13

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