in tap water), which usually settles onto furniture, and is attracted to static electricity generating devices such as CRT monitors. The white dust can be prevented by using distilled water, or a demineralization cartridge in ultrasonic humidifiers. Bottled waters labeled "natural", "artesian", or "spring" may still have their original mineral content. The EPA reports that ultrasonic and impeller humidifiers spread the most mineral deposits and microorganisms, while evaporative and steam humidifers can allow the growth of microorganisms but generally disperse less of them into the air., In addition, a stuck or malfunctioning water supply valve can deliver large amounts of water, causing extensive water damage if undetected for any period of time. A water alarm, possibly with an automatic water shutoff, can help prevent this malfunction from causing major problems. From 2006 to 2011, the disinfectant polyhexamethylene guanidine and other toxic materials were used as a cleaning agent for humidifier water tanks in Korea, leading to severe lung disease. Eighty children died of the disorder and nine adults either died or needed lung transplants. In the two years following the banning of cleaning chemicals for humidifier tanks, there were no new cases. See also Air ionizer The Bronchitis kettle, an early humidifier Dehumidifier Evaporative cooler Hygrometer, for measuring humidity Ultrasonic nozzle References External links EPA.gov Indoor Air Facts No. 8 Use and Care of Home Humidifiers Home appliances