What is an Ultrasonic Humidifier? What is the Difference Between an Ultrasonic Humidifier and an Evaporative Humidifier?

Adding humidity to the air during the winter months can improve the air quality in your home, and it can have significant positive effects on your family’s health. Portable, single-room humidifiers are by far the most popular option for home humidification, accounting for more than 8 million installations every year in the U.S. alone.

Portable humidifiers are essentially of two types: evaporative or ultrasonic.

While both devices are designed to add moisture to the air in your home, they do so in very different ways. Therefore, each type of humidifier has its own drawbacks and benefits.

Let’s take a close look at how ultrasonic humidifiers work, compare them to their evaporative counterparts, and determine which type of humidifier is the right choice for you.

What is an Ultrasonic Humidifier?

An ultrasonic humidifier, despite the sci-fi name, is a very simple device.

It includes a tank of water and two slim ceramic plates or other type of vibrating element. This membrane can vibrate at an extremely high frequency, so high that it is above the range of human hearing (hence the name ultrasonic humidifiers).

These vibrations send microscopic water droplets into the air, where they evaporate, adding humidity to the air in the room.

This way, there is no heating of the water at any point, so these humidifiers are sometimes known as “cool mist” humidifiers.

However, it’s important to note that many evaporative humidifiers can also accomplish evaporation without any heating, and can also be referred to as “cool mist”. The important terms to differentiate humidifiers are ultrasonic and evaporative.

Ultrasonic vs Evaporative Humidifiers

How is an evaporative humidifier different from an ultrasonic one?

To understand, first we need to explain the difference between water vapor in the air, and water droplets in the air.

When water evaporates, it changes from its liquid form to its gas form. As a gas, water molecules are dispersed in the air along with the molecules of the other gases that make up air.

Water droplets, on the other hand, are tiny particles of liquid water that are light enough to be suspended in the air, at least temporarily. The difference is crucial for humidifiers because water droplets can carry substances that were present in the water with them, while water vapor cannot.

Ultrasonic Humidifier

As we mentioned, an ultrasonic humidifier uses high-frequency sound vibrations to produce an extra-fine water mist that is then expelled to add moisture to the room. It's the quieter of the two types of humidifiers. Additionally, ultrasonic humidifiers generally have no filter, which saves on yearly costs. This type of humidifier is considered safer since there is no hot water present in the unit at any time, therefore reducing the risk of scalding significantly. 

However, as with any type of humidifier that does not boil the water to produce a mist, there is a small risk of bacteria being present in it and being released into the room. Making disinfecting the humidifier even more important than with a warm mist humidifier.

Evaporative Humidifier

Evaporative humidifiers have been in use for decades and are considered on of the most common humidifying devices. The mosts straightforward way to humidify a room is to place a pot or jar of water in the room and allow the moisture to naturally evaporate into the air to relieve dryness.

An evaporative humidifier works on the same principle, but it uses a fan to speed up the evaporation process to increase humidity in the room. The built-in fan draws in air that blows through a moist wick filter at the bottom of the humidifier. As the water evaporates into vapor, it's pushed out as water mist or spray into the air to increase humidity.

So evaporative humidifiers, evaporate water inside the humidifier itself, and send water vapor into the air.

Some accomplish this by heating the water into steam, known as “warm mist” humidifiers while other evaporative humidifiers absorb the water through a filter of some kind, then blow cool air across the filter thanks to a fan. This evaporates the water and sends water vapor into the room.

Ultrasonic vs Evaporative Humidifier: The verdict

Whichever method an evaporative humidifier uses, the important thing is that the water is turned to water vapor within the humidifier, leaving any substances that were in the water behind.

If you can’t stand the idea of changing or cleaning your humidifier filter, or you simply want a quieter humidifier, you should chose an ultrasonic, filter-free model. With the increased popularity of this design, you now have several options when it comes to ultrasonic humidifiers. The only drawback? Prepare to combat dust in the room more frequently.

If budget is more important to you, choose an evaporative humidifier, but make sure to change or clean the filter often to keep it running smoothly. Locate filter replacements before buying a humidifier and always have a spare filter on hand.

Main Takeaways:

• Ultrasonic humidifiers employ high-frequency sound vibrations to emit fine mist into the air.
• Evaporative humidifiers utilize a wick or filter with a fan to introduce water vapor into the air.
• Ultrasonic humidifiers tend to be more aesthetically pleasing.
• Ultrasonic humidifiers can disperse minerals and other contaminants into the air.
• Evaporative humidifiers require filter maintenance.
• Ultrasonic humidifiers are quieter than evaporative humidifiers.
• Evaporative humidifiers tend to cost less than ultrasonic counterparts.

The Benefits of Ultrasonic Humidifiers

Ultrasonic humidifiers offer a few advantages over evaporative humidifiers.

• They are very good at humidifying the air.

In fact, they can add so much moisture to the air that this advantage can quickly turn into a drawback, resulting in over-humidified air that causes dampness and mold. This is why it is crucial for an ultrasonic humidifier to have a humidistat that can detect humidity levels and shut off the humidifier if the air has too much moisture in it.

• Ultrasonic humidifiers can be made extremely small and compact.

Because the humidifying mechanism is so simple, the limiting factor for how small an ultrasonic dehumidifier can get is basically the water reservoir. So they are the right choice if you need to fit your humidifier in a very tight space.

• An ultrasonic humidifier is much quieter than an evaporative humidifier.

However, the vibration of ultrasonic humidifiers can emit an audible hum, especially noticeable in a very quiet bedroom.

• Ultrasonic humidifiers do not generate any heat.

This makes them safer than steam humidifiers that boil water to produce water vapor. This could be really important if the humidifier is used in a child’s room. Still, many evaporative humidifiers also function without any heat and without boiling water.

• You never have to replace a wick or filter on an ultrasonic humidifier.

The filter in an evaporative humidifier eventually collects a build-up of minerals left behind by the water, especially if hard water (water with a lot of minerals dissolved in it) is used. These filters must be changed regularly, adding effort and cost.

• Ultrasonic humidifiers consume very little electricity.

Drawbacks of Ultrasonic Humidifiers

All the drawbacks of ultrasonic humidifiers stem from the fact that the humidifier releases water droplets into the air instead of water vapor. This can cause several issues.

While most of the water droplets will evaporate into water vapor, some of them will settle out of the air and onto nearby surfaces before they have a chance to evaporate. This will be more of a problem if the air in the room is cold or if the air already has a high moisture content. The result can be a damp area or even a puddle of water near the humidifier. That’s one of the main reasons why ultrasonic humidifiers need to be placed on a shelf or dresser instead of on the floor, so the water droplets have more time to evaporate before settling.

A much bigger problem is the fact that any substances in the water will be sent into the air along with the water droplets. These substances can be either minerals or biological pollutants.

Minerals in the air from Ultrasonic Humidifiers

Minerals are present in all non-distilled water, and if you know you have hard water in your area, it means your water has more minerals than it probably should. These minerals are carried into the air along with the water droplets when an ultrasonic humidifier is at work (while in an evaporative humidifier, the minerals are left behind).

At the very least, these minerals will settle out of the air and leave a fine white dust on surfaces near the humidifier. In the worst case, anyone in the room can inhale these minerals.

Because of the concern that people can inhale the aerosolized particles in the white dust, studies have examined the effects on the lung tissue using tap water in ultrasonic humidifiers. Though the particles did not cause severe inflammation of the lungs in mice, the study concluded that distilled water should be preferred to tap water to remove any risk. While distilled water still contains some mineral content, it will likely contain lower mineral content than most tap water as distillation is the most effective method for removing minerals from water.

Risk of microbial exposure

If the water in an ultrasonic humidifier is contaminated with bacteria or mold, it will emit those substances, exposing anyone in the room to them. This can result in allergic reactions or the spreading of disease, sometimes known as “humidifier fever”.

While all humidifiers have the potential to become breeding grounds for bacteria or mold. However, the EPA found that ultrasonic humidifiers tend to disperse more biological contaminants than evaporative humidifiers.

There is another potential problem with ultrasonic humidifiers unrelated to water. While the vibrations they generate may be too high frequency for you to hear, they might be within the hearing range of your dog. There have not been any studies on the effects of ultrasonic humidifiers on dogs, but if you plan to use one in a room with dogs, the sound may be painful or uncomfortable for them.

Ultrasonic Humidifier concerns for kids and babies

Many people choose to use a humidifier in a baby’s room or kid’s room, especially when they have respiratory infections. However, there is no solid evidence that humidifiers can relieve symptoms for young children, though it can make them feel better.

A study drew attention to the fact that the lungs of babies and small children may be more sensitive to the chemicals produced by an ultrasonic humidifier.

All in all, millions of parents do purchase humidifiers for their sick children and the risk of this type of illness is probably almost zero.

How to clean an Ultrasonic Humidifier

The solution to reducing risks for any of the problems mentioned above is regular and thorough cleaning and disinfecting of the humidifier. The EPA offers a simple guideline:

“Clean portable humidifiers every third day. Empty the tank and use a brush or other scrubber to clean it. Remove any scale, deposits, or film that has formed on the sides of the tank or on interior surfaces, and wipe all surfaces dry.”

Choosing the Right Ultrasonic Humidifier

If you decide to use an ultrasonic humidifier, which one you choose will depend on the room you need to humidify and any additional features you want.

Very few portable, single-room humidifiers have output ratings, mainly because these can vary a lot based on air pressure, temperature, humidity levels and other factors. A more critical factor when selecting a humidifier is the size of the reservoir, and how often it will need to be refilled. If you are humidifying a large room that gets very dry, you will want a humidifier with a larger reservoir, especially if you will use it in a bedroom. You do not want to have to get up in the middle of the night to refill your humidifier. If your room is very small, you can use a humidifier with a small reservoir

Another very useful feature is a humidistat, which will automatically shut off the humidifier if the humidity levels get too high. This is very important for preventing excessively humid air that can lead to dampness or mold growth.

Some ultrasonic humidifiers can be also used with aromatherapy oils, so look for that feature if it is something you may enjoy.

Maintain Acceptable Humidity Levels for Good Air Quality

Maintaining good humidity levels in a dry climate or during winter is an important element of good indoor air quality. Excessively low humidity can lead to dry, scratchy throats, coughing and dry skin. Wood floors and furniture can be damaged by low humidity. And studies have found that low humidity actually increases the spread of bacteria.

When using a humidifier, it is important to reduce the risk of introducing air pollutants like mold and bacteria in the air. It is also very important that relative humidity levels stay within the ideal range of 30-50%, or at the very least, below 60%. This is to prevent excess mold growth and dust mites in your home. An additional way to maintain air quality is to use an air purifier like Koru.

Portable humidifiers are a good option for humidifying specific rooms in your house, and ultrasonic humidifiers do offer some advantages over evaporative humidifiers. Regular cleaning is important no matter what type of humidifier you decide to use, especially to maintain good air quality in your home.

A conclusive note

By now, you should know which device will work better for your circumstances when you’re choosing between an ultrasonic vs evaporative humidifier. As you learned, both can be beneficial for your health and home. And in many instances, people choose to use both indoors to get the comfort and relief and they need.