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If you’re in the market for a humidifier, you are probably wondering if there are any differences between the types available to consumers. There are two main types of cool mist humidifiers: evaporative and ultrasonic. Let’s take a brief look at each type and how they work differently to provide moisture to the air in your home.

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Evaporative Humidifiers

Evaporative humidifiers utilize a fan and a filter (also known as a “wick”) to create water vapor through the natural process of evaporation. After filling the humidifier tank with water and turning it on, the fan functions to bring in air and push it through the moistened wick, which evaporates the water within the machine and releases it into the room. As the air is pushed through the wick filter and the water is turned into vapor, particles such as dust or minerals are left in the machine and not dispersed into the air.

Ultrasonic Humidifiers

Ultrasonic humidifiers work very differently than evaporative humidifiers while producing a similar result. Instead of using a fan or filter, ultrasonic humidifiers use high-frequency vibrations to release tiny water droplets into the air. As the droplets are released, they evaporate into vapor, which makes the room more humid. However, since ultrasonic humidifiers lack filters and because the water droplets evaporate after leaving the machine, there is more of a chance that minerals from the water (or even mold or bacteria from improper care) can be released into the room and leave white or gray dust. With this in mind, it’s best to clean the machine regularly to prevent mildew and use distilled water in the tank.

Which Should You Choose?

Now that you know how each humidifier works, you are probably wondering which one is best for your home. We’ve separated the following points into three categories: size, sound, maintenance, and price.


Evaporative humidifiers are generally larger than ultrasonic humidifiers due to the fan and filter, so they may not be a good option if you have a smaller space to work with. Ultrasonic humidifiers tend to come in a variety of compact shapes and sizes because of their simplistic design.


Most ultrasonic humidifiers produce little to no noise due to the high frequency of the vibrations. Even in the case that some ultrasonic humidifiers produce a low humming noise, they are typically much quieter than the fans of evaporative humidifiers, which tend to emit more white noise. However, if you or someone in your household need white noise to sleep, an evaporative humidifier could act as both a white noise machine and humidifier.


Both humidifiers require regular cleaning and maintenance to prevent the growth of mold, mildew, or bacteria and the buildup of minerals. Evaporative humidifiers will need to have their filters cleaned or replaced every few months depending on the frequency of use, and both types of humidifiers should ideally be wiped down at least once a week. Because ultrasonic humidifiers don’t have wick filters to catch particles, it is especially important to wipe down and dry the interior parts to prevent mineral buildup or mildew.


Both types of humidifiers come in varieties that are priced for consumers of all budgets. However, ultrasonic humidifiers tend to be more expensive upfront, while evaporative humidifiers will require the regular purchase of replacement filters over time. While these filters are relatively affordable, the recurring cost is something to take into account when compared to the one-time cost of an ultrasonic humidifier.

When it comes to buying a humidifier, your decision should rest in the factors that matter most to you. Whether you care most about cost, size, or sound level, there’s a humidifier that will meet your needs.