This type of humidifier works ultrasonically, which is very quiet and puts out a lot of moisture. The vibrating membrane that creates the mist does get clogged over time with minerals if you have hard water. It can be cleaned to a point, but eventually it might stop misting. You will find a fine layer of sticky mineral gunk all over the room (on any exposed surface), unless you have soft water. There are additives you can put in the water to minimize this. Small rooms may get too humid unless it's on the lowest setting. We have been pleased with this one so far.