Homedics Ultrasonic HumidifierULTRASONIC TECHNOLOGY The Homedics Ultrasonic Humidifiers for large rooms have high frequency technology that converts water into a fine, evenly dispersed mist; ideal as a bedroom humidifier and for family rooms up to 426 sq. TOP FILL HUMIDIFIER The easy to fill tank holds 1. 47 gallons of water and provides up to 70 hours of cool mist runtime per fill QUIET & CONVENIENT Perfect for nighttime use with whisper quiet operation and built in night light;