Air-O-Swiss Refurbished 7133 Ultrasonic Humidifier - Warm and Cool Mist Humidifies the air in rooms up to 650 sq ft (60m) Make the choice of cool or warm (104-DegreeF (40-DegreeC)) humidification Modern design with empty indicator Transparent water tank (water level clearly visible) Built-in hygrostat for controlled humidification