The Lennox HCWP3-18A humidifier was made by Aprilaire for Lennox. Since parts cost is lower for the original manufacturer (Aprilaire) we are carrying the Aprilaire name parts to save you money. This is a power style wholehouse humidifier. It can be mounted on the supply or the return duct system of a furnace or air handler. This model requires replacement of the humidifier filter at least once per year.