The young, the elderly, and those people with lung diseases or respiratory allergies may be particularly susceptible to certain types of airborne pollutants. However, if you follow the recommendations for the use and care of home humidifiers provided in this fact sheet, the potential for dispersal of microorganisms and minerals from your humidifier should be reduced. The Federal government has not concluded that using tap water in ultrasonic or impeller humidifiers poses a serious health risk. However, researchers have documented that these humidifiers are very efficient at dispersing minerals in tap water into the air. Most importantly, minerals in tap water may increase the development of crusty deposits, or scale, in humidifiers.
Scale can be a breeding ground for microorganisms.
Retarding the growth of scale is the most compelling reason to find alternatives to tap water. While distilled water still contains some mineral content, it will likely contain lower mineral content than most tap water. Distillation is the most effective method for removing minerals from water. Two additional demineralization processes, deionization and reverse osmosis, remove most of the minerals from water, but are generally less effective than distillation. Water demineralized by these two processes would, on the average, be expected to contain a higher mineral content than distilled waters.