what is the black sooty residue coming from my ultrasonic air purifier? It has always produced this material on its plates, however lately I find tiny specks on the carpet and when I brush my hand over the surface of any nearby tables I get it on my fingers. Does it need more frequent cleaning? Even the walls one foot away have a light darkm coating which is brushed off easily. Email: frz112lc@aol.com Thanks Ron
