For those of us with some sinus conditions, a humidifier can be a blessing in the winter months when the air is dry. Unfortunately, an unclean humidifier can be a hazard to your health. The moist area of a humidifier is the perfect place to grow bacteria. And water vapor is the perfect carrier of that bacteria. There are four types of humidifiers: ultrasonic, cool mist (impeller), evaporative, and steam vaporizers. Of the four, the safest are evaporative and steam vaporizers because the evaporated water cannot carry bacteria as well as the tiny water droplets the other two create. But they can still harbor microorganisms in the tank. Use of a bacteriostatic additive and regular cleaning can nearly eliminate any risk of infection. The following is the best way I have found to clean a humidifier. The humidifier in the pictures is an evaporative wicking console humidifier. But you should be able to use the advice here to clean any humidifier. Read How to Clean a Humidifier.