A cool mist humidifier has no heating element installed in the base unit. Instead of dispersing moisture in the form of steam, these devices use a built-in fan to blow air through a damp filter—the water and air mix to form a vapor, which the fan propels into the air. Because humidifiers are designed to use tap water, bacteria and mineral deposits may build up over time. It's important to clean your cool mist humidifier on a regular basis, in order to keep it in proper working condition.
Turn off the humidifier and disconnect its power cord from the electrical outlet. Move the humidifier to a well-lit work area near a sink and water tap. Use a clean, dry cloth to wipe down the exterior of the device. Wash and dry your hands thoroughly before proceeding.
Remove the top housing and the water tank from the humidifier's base. Empty the contents of the water tank into the sink. Fill the tank with approximately one gallon of water. Add a teaspoon of bleach to the water. Allow the solution to sit in the tank for approximately 20 minutes—cover the opening and shake the tank every two or three minutes to thoroughly disinfect the interior.
Pour out the cleaning solution and rinse out the interior of the tank with cool water. Repeat the disinfection process with the humidifier's water basin.
Fill the humidifier's base with undiluted white vinegar—allow the vinegar to sit for approximately 20 minutes. If your humidifier comes equipped with a separate pickup tube, place the tube in a bowl of undiluted white vinegar and allow it to sit for the same amount of time. Use a clean cloth or small brush to wipe away any scale deposits from the sides of the base.
Pour out the vinegar and rinse the base with cool water—rinse off the pickup tube as well, if applicable. Use a clean cloth to wipe away any residual moisture. Refill the water tank and replace it in the humidifier's base. Replace the top housing. Return the humidifier to its original location and reconnect the power cord.
Empty out the water tank after you turn off the humidifier. Leaving the tank full and unused provides a suitable environment for bacterial growth. Be sure your hands are completely dry prior to handling the humidifier's power cord. Avoid allowing any water to enter the humidifier's top housing. If this occurs, extract the water and allow the housing to dry completely before attempting to use the humidifier again.