What is an ultrasonic humidifier?

You’re probably familiar with the common types of humidifiers that have been in use for many years.  Warm mist humidifiers boil water to release steam vapor.  These use a fair amount of electricity, and can be a burn hazard.

Evaporative or wick humidifiers soak water into a cloth-like substance and pass air through it.  These types of humidifiers become moldy if the wick isn’t allowed to dry completely between fillings, and the wick can quickly become encrusted with minerals necessitating frequent replacement.

An ultrasonic humidifier uses a metal diaphragm vibrating at an ultrasonic frequency, much like the element in a high-frequency speaker, to create tiny water droplets about one micron in diameter. An ultrasonic humidifier is usually silent, and produces a cool fog.  Because the water droplets are so small, they evaporate into the room air almost immediately upon leaving the humidifier.  As a result, you don’t have to be concerned about nearby objects (or the carpet under the humidifier) becoming moist.

More specifically (warning, technical details follow: you can safely skip this scary paragraph if desired), a piezo-electric transducer is used to create a high frequency mechanical oscillation in a body of water. The water tries to follow the high frequency oscillation but cannot because of its comparative weight and mass inertia. Thus, a momentary vacuum is created on the negative oscillation, causing the water to cavitate into vapor. The transducer follows this with a positive oscillation that creates high pressure compression waves on the water’s surface, releasing tiny vapor molecules of water into the air.  (Technical details finished)