I tried an ionization based portable air filter in the 80's and found that it quickly caused a thin buildup of difficult to remove residue on everything in the room (including the walls/ceiling/windows).
After going through a few gallons of TSP I gave it away.
Gregm:
We have open windows whenever the temp's drop to 70, or below.
Being located 11 miles from the ocean (West Hollywood) there is also a nice subdued marine layer most evenings.
This said, what's emptied out of the vacuum canister is a bit frightening.
DeKay