For rooms up to 400 square feet, the Venta LW25 Airwasher humidifies dry room air while simultaneously purifying it by removing dust, pollen, pet dander, and other airborne pollutants down to 0.3 microns in size. The Venta Airwasher is both a filter-free evaporative humidifier and filter-free air purifier, all in one lightweight unit. Additionally, Venta Airwashers do not produce white dust common with other humidifiers due to the fact that we use Cold Evaporation technology. Perfect indoor air quality cleansed by a Venta Airwasher helps to improve concentration, reduce headaches and common cold symptoms, as well as keep allergies under control against dust mites, animal dander, and pollen. This compact 2-gallon humidifier is powerful enough to work with indoor spaces of up to 400 square feet, perfect for a living room or master bedroom, and is designed to resist over-humidifying the interior.