To avoid any bacteria buildup inside humidifiers simply, unplug  the device and remove the water tank. Saturate a clean cloth with hydrogen peroxide and use to wipe down the base. Now fill with 1 gallon of water and 1 pint of hydrogen peroxide. Let this sit for about a half hour then rinse with fresh water. This will kill any harmful microorganisms. Doing this every 3 days is ideal but not practical. So do as you feel it’s needed!