I’m so happy with this air purifier. It runs quietly, unless you set it to high (there are 3 levels, plus auto). My son likes high because it sounds like white noise. He coughed on it by accident (he’s had a cough for a few days), and the impurity detector light changed color to indicate impurities in the air! It stayed that way for a bit, until the air was filtered. I thought that was a cool validation that it works!