HM4125-B5, 40M2 Black & Decker Air Humidifier Concerning this item POWER: 30W, covering up to 40m² of space. CAPACITY: 4.0L integrated tank that provides 8–14 hours of continuous mist EFFICIENT: High-performance ultrasonic system for geothermal treatment with an adjustable knob that controls mist flow up to 350 ml/h