I have my filter device on the slowest setting 24/7 in the room where I work all day at home. I have coughed much less since it has been there. It took about ten months before the light went on and I had to change the filters. They were easy to fit, although the old ones were VERY dusty. The device is very quiet. My only disappointment with my order of the replacement filters is that it was fulfilled by the big river company and if I wanted to give them my money, I would not be on the Bay.