As warm air passes through the humidifier pad and water flows through it, natural evaporation takes place. This creates comforting humidity which is distributed throughout the house by your heating system. Optimal generation of comforting moisture - Working together, Totaline's water solenoid valve, water metering orifice, water distribution tray and aluminum humidifier pad efficiently generate maximum levels of comforting moisture. Simple, infrequent maintenance - Totaline humidifiers are designed for easy serviceability. In most instances it takes less than half hour since maintenance ( including changing the humidifier pad) is performed once a season. Unlike portables, there are no reservoirs which need to be frequently cleaned and refilled. Long lasting high quality components - With proper maintenance, your humidifier will last for many years. That's because it's designed with durable UV and corrosion resistant plastic. This plastic resists deterioration even when exposed to Ultraviolet light sources common in many systems today. Three humidity control options - Choose between 3 separate control options; the humidistat, the Humiditrac and the Thermidistat control. Each option provides precise control over the humidity levels in your home. Quiet operationNearly silent operation is the result of Totaline Humidifier's precision engineered fan and motor combinationin the large fan powered unit. In all Totaline units, air is quietly drawn through the humidifier pad which efficiently turns water into water vapor to humidify your home.