> My air purifier is built into the furnace ductwork

That's neat! Do you know if the ozone is produced before or after it reaches the blowing mechanism? I ask because if it is produced before, like right after the air intake, that's a really great setup for keeping your ductwork mold and mildew free. I've wanted to buy such a system but keep holding out for things to get cheaper... in the meantime, I use an ecoquest "FreshAir" model sitting on top of the fridge.