The Aprilaire 360 humidifier requires annual maintenance consisting of replacing the humidifier filter (water panel evaporator) and washing out the pad frame and water distribution tray. The Model 360 is designed especially for any residence, condominium, town house, or apartment that does NOT have ductwork or uses hot water heating. It is installed through the wall (like a window unit) and is completely independent of the heating system. Often installed in a closet wall so it sucks dry air out of the closet, adds moisture to it and blows humid air into the hallway.