http://www.engadget.com/2006/05/10/report-ionic-air-purifiers-create-cough-cough-smog/
I got one of those for christmas the other year - a small one that you can use in your car or bathroom, etc. But the ozone made me nauseous when I tried it the first time in our really large rec room.
Then again, a friend of mine has two of the large ones in her living room and it doesn't bother me.
YAOBSC
cough cough smog is the best kind of smog.