The Airsonic GS380 Ultrasonic Humidifier produces 380ml water vapour per hour from its 6 litre tank, giving 15 hours of continual use at full power. Ideal for raising humidity to the correct level, the ultrahigh frequency vibrations generate an ultra-fine mist. At less than 35dB the unit is whisper quiet and can also be run with an external hygrostat. Unlike the humidifiers that boil water, these water droplets will contain any impurities that are in the reservoir, including minerals from hard water (which then forms a difficult-to-remove sticky white dust on nearby objects and furniture). Any pathogens growing in the stagnant tank will also be dispersed in the air. Ultrasonic humidifiers should be cleaned regularly to prevent bacterial contamination from being spread throughout the air.