I'm pretty sure that anything that comes in contact with high concentrations of O2 must be 02 clean. So, that would certainly mean that the air produced by the compressor used in partial pressure blending would have to meet 02 clean standards, as would the tank and any equipment in the air path, like fill whip, etc. Not just when filling partial pressure tanks, but all the time, because if non-02 clean air was flowing through the whip, I would think the whip would no longer be 02 clean.
Now, an interesting question to me (maybe obvious to someone who knows more) is, lets say your compressor and air path is 02 clean, and you use it to fill a non-02 clean tank with 02 clean air. Is there any sort of cross contamination to the fill whip? It's a pretty paranoid scenario.