I owned one of these years ago when I lived in CA and the air quality was very bad. I had an efficiency apt and would close off the bathroom to keep the amount of air cleaned controlled. When I would go into the bathroom from the main room it felt like I was walking in a parking lot at 5pm. The air in the main area smelled like a spring meadow. I live with very clean area now in IA except during plowing seasons. but this HEPA does seem to help with allergies I bought one for me and one for my grandson who graciously shares his colds with me.