Instruct: Classify Amazon reviews into positive or negative sentiment
Query: ineffective

I bought this humidifier based on the reviews and (mistakenly) thinking it was an ultrasonic humidifier. I have a room that is 25x14 with 9 ft. ceilings. Even at the highest level this humidifier doesn't make a difference, except in the noise level - which is deafening. At the lowest level it doesn't work at all - even when I leave it on all the time.I also discovered today that mold was accumulating in the filter that I replaced less than a month ago.Totally ineffective, is my impression of the machine.I'm off to find a large capacity ultrasonic humidifier.