Lennox furnace maintenance, furnace is operating very well . Furnace filter needs to be changed by the end of April , she is using a 6672 now but would like to change to 6670 . Uv bulb need to stay unplugged . House humidifier is about 20% rh , humidifier is operating fine but damper is was closed . Damper will need to be closed at the end of winter . I have also recommended Andrew be the technician returns for any future work .