The Herrmidifier 4000 is a wholehouse humidifier designed to be attached to your furnace ductwork. Annual maintenance on the Herrmidifier 4000 humidifier consists of replacing the humidifier filter pad and washing out the rest of the humidifier. We stock all the available parts for the Herrmidifier 4000 humidifier. This is an old obsolete model so parts NOT shown are out of production and no longer available.