This is an excellent product, however my purifier emits a faint high pitched sound that sounds like my tinnitus. Thus, it is not in my bedroom anymore. I do continue to run it constantly, however, but only in the front room of my house.
When I change the filter it's obvious to see it has been trapping quite a bit of stuff. I just don't know why there is no way to get the warning red light to go off. When I first got the purifier it was always green.