M.B.
I have severe allergies and chemical sensitivies and find that the Holmes HEPA air purifier (we have one in every room) does help alot. We also have pets and while it doesn't entirely reduce the dirt and debris from them, it helps. If you aren't chemically sensitive, likely you don't need the more expensive ones like IQAir, which are definitely better (that's on my wish list as they're 5x the cost of the Holmes brand). You do have to change the charcoal filter on the Holmes at least every ninety days - those aren't too expensive. But, the HEPA filters themselves also require annual replacement and that will cost you $30 - $45 per unit (depending upon the size of the unit).