Unfiltered, totally unfiltered?? Blimey....
There was a lot of fuss a few years ago about BAe 146's creating very bad symptons and the operator(s) denying everything...
One of the things that came out of this was
reduced (inadequate
) airflow due to fuel saving measures... it being suggested that this was becoming quite common, to reduce the total changes of cabin air.
..it being relatively easy to quote average air use per pax when resting, as opposed to what might be a decent factor over and above the minimum required. Remembering that we're cruising at what, a cabin altitude of 8,000 ft, then people will be breathing somewhat larger volumes of air than normal, and imagine this all taken into account - but nevertheless that is a lot of people in a small space...
Personally think a lot more care should be taken over pax (and crew) air quality... this IS supposed to be man's ultimate technolgical form of transport - let's get it right shall we and stop the spin
Even Dyson vacuum cleaners have pretty good exhaust air filtering...