Indoor air pollution has become an issue of growing importance for the scientific community. A recent publication of a report of the US Environmental Protection Agency (EPA) showed evidence that portable ultrasonic humidifiers may play a significant role as health hazards as far as indoor air pollution with heavy metal particles is concerned. Especially if the manufacturers' guidelines are not followed strictly and the device is operated with tap water, indoor particle concentrations may reach up to 50 times US outdoor standards for toxic particle concentration. This paper highlights potential risks and benefits of various types of humidifiers, both in private and hospital settings, emphasizing that risks of air humidification in certain situations might outweigh anticipated benefits. The health policy implication of these findings should lead to a more critical application of air humidification in the health care environment and in addition to that, promote better information of the customer about safe operation and useful indications of such devices.