Humidifiers need to be cleaned frequently as these devices deal with moisture. And moisture if left untouched can form moss and other bacteria. Every humidifier needs to dry from all its water contents and air-dried at least once in two weeks. Furthermore, it is advisable to clean your humidifier's water reservoir with cleaning agents such as bleach or special humidifier cleaner. Also, you can clean the reservoir with the help of vinegar. Although that being said the best advisable option would be distilled water. That is just the basic cleaning method of a humidifier. As different types would call for different cleaning ways. As a few of the humidifiers can be washed in a dishwasher while others cannot. Moreover, if your humidifier has a filter then those filters require replacement as well.