ULTRASONIC HOLMES HUMIDIFIER: This energy-efficient Holmes ultrasonic humidifier propels visible, cool mist, with a virtually silent, filter-free operation EASY TO FILL, CLEAN, AND USE: This Holmes ultrasonic humidifier features a top fill design for easy filling and cleaning; 2 speed settings provide optimal comfort. 15-HOUR RUN TIME: The 0.28-gallon capacity water tank offers a 15-hour run time on a full tank and low setting.