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