I purchased two Blueair devices to use in the summer when we experience heavy smoke from wildfires (NW Montana).  I put one in my utility room with my cats' litterboxs and was surprised how much dust the litterboxs generate. I didn't realize that until I saw how much dust the blueair was absorbing. I like the fabric external filters since I can see that the blueair is working and they are very easy to clean by tossing them in the washer. One other comment: I recently thought I had a problem with an order, which turned out to be my fault, not the fault of Blueair, and I received really excellent customer service.  Thank you to Casi Kristant at Blueair.  She did a great job so I will continue to be a loyal customer!