For rooms up to 800 sq. ft.The Venta Airwasher LW45 humidifies dry room air while simultaneously purifying it by removing dust, pollen, pet dander, and other allergens.Venta Airwashers do not use filters; water is the filter.This makes the products easy to maintain and clean.Additionally, Venta Airwashers do not produce the "white dust" common with other humidifiers due to the fact that we use cold water evaporation technology.