I have been beating my head against the wall fora couple of weeks now concerning my dirty glass issue. Cleaned the stove, changed pellets, adjusted air fuel, changed pellets, cleaned chimney with no change. My glass would get dusted and dirty over night. I finally looked more closely at the air wash system which consists of a small groove around the metal support for the window . I cleaned that out with a utility knife blade and pulled all sorts of black goup out of it. I suspect it was from the non stop cleaning cleaning with liquid cleaner....liquid dribbles down and gets rubbed into this seem. Much better now and i know my stove very well after all the reading and cleaning (silver lining).