First I want to say that I have only had this unit for 10 days. My experience with Bissell was terrific. I placed my order on a Wed. and received it the following Monday. The unit was very easy to set up and has been working well ever since. My house doesn't have an internal air exchanger ( having been built in the 70's) and we have made many improvements to the energy efficiency, but the air inside during the seasons when we don't open windows, can be stuffy. I really notice it when I leave and come back later. We don't smoke or have dogs, I just think it's a air circulation problem. This air purifier has made a difference. I have not been noticing a stuffy smell when I come home. I sneeze less and breath better at night. I hope I still feel this way about my Bissell air purifier months from now. I may update this review in the future. Very happy right now!