A Beginner Guide To How An Ultrasonic Humidifier Works

Ile Kauppila

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Ile Kauppila

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Josh Mitchell

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I love my ultrasonic humidifier. I live with some breathing issues and the little miracle machine has made my life a lot easier by maintaining proper humidity levels.

If you’re new to humidifiers, though, you might wonder how ultrasonic humidifiers do their job.

And what makes them “ultrasonic” anyway?

Knowing how any humidifier works helps you get more benefits from it — and the same goes for ultrasonic units.

In this guide, I will teach you how ultrasonic humidifiers work so you can use them effectively and safely.

Key Takeaways

  • Ultrasonic humidifiers, a type of cool mist humidifiers, turn water into fine mist by using ultrasonic soundwaves.
  • Ultrasonic units are very safe to use since they do not use any hot components or boiling water (unlike warm mist humidifiers).
  • They are compact and portable devices but they do not have any filters. Hence you must use them with distilled water.

How Do Ultrasonic Humidifiers Work? (The Science Explained)

How do ultrasonic humidifiers work

So, how does an ultrasonic humidifier actually work?

The answer gets a bit technical, but don’t worry — I will keep this simple enough for anybody to understand.

Let’s dive into your ultrasonic humidifier’s water tank and see how it adds moisture to your home.

Principle Of Operation – Soundwaves

An ultrasonic humidifier transforms liquid water into fine, tiny water droplets that it expels into indoor air to raise humidity levels.

As you might guess from the name, the humidifier achieves this effect by using sound.

The two main components of an ultrasonic humidifier are the water reservoir and a vibrating mechanism called a diaphragm, consisting of a ceramic or metal plate.

When you turn the unit on, the diaphragm vibrates at high speed, generating extremely high-frequency sound vibrations.

These vibrations break the body of water in the tank into water droplets.

As this fine mist rises into the air, the tiny droplets evaporate and turn into water vapor, humidifying the room.

All of my talk about high-frequency sound might make you think ultrasonic humidifiers are noisy — but they’re actually very quiet.

Important Note:

The ultrasonic sounds are beyond the human hearing range, so they will not disturb you.

Note that your pets might hear the unit, though. My dog didn’t quite know what to make of it at first, but she’s gotten used to the humidifier!

The Science Behind Mist Production In Ultrasonic Humidifiers

But how can sound produce mist from water?

This process relies on two primary principles: cavitation bubble implosion and capillary wave theory.

I know that sounds pretty science-y. Don’t worry, it’s actually very simple.

Cavitation Bubble Implosion

The vibrating plate causes pressure changes in the surrounding water, which forms tiny pockets of air called cavitation bubbles.

These air bubbles aren’t stable and they quickly implode or collapse in on themselves.

This implosion breaks the water’s surface, sending microscopic water droplets into the air. (1)

TL;DR: Step 1 of the processes is formation of tiny unstable air bubbles due to vibration that quickly pop producing vapor.

Capillary Wave Theory

As cavitation happens, the vibrating diaphragm — together with the collapsing air bubbles — causes broken capillary waves on the surface of the water tank.

The crests of these small waves fling the resulting water aerosol out through the humidifier’s mist nozzle.

The water evaporates in the air, adding moisture to the indoor space. (2)

TL;DR: Step 2 of the process involves capillary action through which air absorbs the vapor and carries it out. 

What’s The Difference Between Ultrasonic And Evaporative Humidifiers?

The primary difference between an evaporative humidifier and an ultrasonic humidifier is how they hydrate the air.

ultrasonic vs evaporative humidifiers

As I explained, an ultrasonic humidifier releases water droplets into the air by using ultrasonic vibrations.

Evaporative humidifiers, as their name implies, produce water vapor through evaporation.

They suck up water from the tank into a wick filter and use a fan to blow cool air over it, pushing water vapor into your living space.

Although ultrasonic humidifiers use a more intricate working method, their components are relatively tiny.

Therefore, they can be smaller and more compact than other humidifiers.

An ultrasonic humidifier is also much quieter since there’s no whirring fan.

On the other hand, the filter of an evaporative humidifier removes dissolved minerals and impurities from water.

This way, the device avoids introducing air pollutants into your home.

They don’t clean the air like an air purifier, but evaporative humidifiers are more hygienic than ultrasonic and can help maintain good air quality.

Keep that in mind if you suffer from allergies or asthma (like I do).

Check out my detailed guide to learn more about the differences between ultrasonic vs. evaporative humidifiers.

TL;DR: Evaporative humidifiers use a wick filter, ultrasonic humidifier do not. The former adds a layer of air filtration, the latter is quieter and does not require regular maintenance.

Do Ultrasonic Humidifiers Really Increase Humidity Levels?

Yes, they do! Ultrasonic humidifiers work exceptionally well to increase air moisture and maintain air quality.

They are hands down my favorite type of humidifier.

Ultrasonic humidifiers are very quiet and compact devices, which makes them a great choice for humidifying your bedroom (that’s where I keep my unit).

Unlike steam humidifiers, ultrasonic machines don’t boil water and produce a cool mist, so they’re also a safe choice for a child’s room.

Some modern ultrasonic humidifiers have a heating element, though. As such, the device can function as a warm mist humidifier as well.

If you’re looking for flexibility in your humidifier, a high-end ultrasonic device is my recommendation.

However, there are two ultrasonic humidifier concerns you should be aware of. The first is that they might be too good at humidifying the air.

Important Note:

Pick a device with a built-in humidity monitor for preventing excessively humid air that could increase the levels of dust mites, mold, and bacteria.

My second warning is that ultrasonic humidifiers don’t have filters.

If you live in an area with hard water like I do, they can blow fine white dust all over your home, in addition to any possible bacteria found in the water.

Always use distilled water in your ultrasonic humidifier to prevent these issues.

TL;DR: For those who do not want to deal the burning hot steam of warm mist humidifiers, ultrasonic humidifiers can work perfectly to increase humidity levels.

Pros And Cons Of Ultrasonic Humidifiers

  • Excellent at humidifying the air
  • Small & compact
  • No noise
  • Effectively relieves coughing, congestion, and dry skin
  • Can reduce airborne pathogens and viruses
  • No heat makes them safer around children
  • Good for your skin
  • Easy to clean and maintain
  • Ultrasonic humidifiers consume very little electricity
  • Helps keep plants and wooden furniture healthy
  • No filter for mineral scale absorption
  • Could result in over-humidified air unless carefully monitored
  • High initial price
  • Collects bacteria if not regularly cleaned

How To Make Any Ultrasonic Humidifier More Effective

You can make your ultrasonic humidifier work as effectively as possible with a few simple tricks and maintenance procedures.

Here are my five top tips for boosting the efficiency of ultrasonic humidifiers.

Clean Your Ultrasonic Humidifier Regularly

Ultrasonic humidifiers tend to develop mold and bacterial contamination that could introduce pathogens to your home.

Clean an ultrasonic humidifier weekly with water and white vinegar and allow it to dry properly before use.

If you’re a clean freak like me, though, there’s absolutely no harm in washing the unit every day.

Use Only Distilled Water

With no filters, ultrasonic humidifiers can spread mineral dust and bacteria found in tap water into your home.

What kind of water for humidifiers

These could lead to negative health effects like respiratory infections.

Use distilled water in your machine to maintain good indoor air quality.

Avoid Small Enclosed Areas

If you place your unit in a small enclosed area, like a tight corner, it can’t distribute moisture effectively.

The humidity in the corner could rise too much and lead to excess mold growth. Place your humidifier in a central, open location.

Place The Humidifier In A Secure Location

Keep your ultrasonic humidifier on a stable, raised surface to put it out of the reach of kids and pets.

The elevated location also helps the device spread moisture into your home more effectively.

Look For A Humidistat Feature For Better Humidity Control

Try to buy an ultrasonic humidifier with a humidistat feature and turn it on.

This component lets the humidifier monitor humidity levels and turn itself off when necessary to prevent the growth of mold and bacteria.

TL;DR: Regular maintenance, using only distilled water, choosing the right location and having the humidistat built-in can improve a humidifiers effectiveness.


Is It Safe To Use An Ultrasonic Humidifier In A Baby’s Room?

Yes, an ultrasonic humidifier is safe to use in a baby’s room.

However, I recommend only using cool mist humidifiers around babies, ultrasonic or otherwise.

Warm mist humidifiers could cause a burn risk. (3)

What Is The Difference Between An Ultrasonic Humidifier And A Diffuser?

A diffuser is a much smaller device used with essential oils to add fragrances and scents to a room.

Although ultrasonic humidifiers and diffusers use the same vibrating mechanism and water, diffusers aren’t powerful enough to humidify rooms.

Which Is Better: Cool Mist Or Ultrasonic Humidifier?

Ultrasonic humidifiers typically are cool mist humidifiers, but they are often compared to evaporative humidifiers.

An ultrasonic humidifier can be more efficient and cheaper to maintain, while evaporative humidifiers are generally more hygienic.

What Kind Of Humidifier Do I Need For Congestion?

If you suffer from congestion, a cool mist humidifier — like an ultrasonic humidifier — is the best.

Cool mist humidifiers have been shown to help with congestion and coughing more so than warm mist humidifiers. (4)

Wrapping Up How Ultrasonic Humidifiers Work

Like I said in the beginning, I love ultrasonic humidifiers.

These state-of-the-art humidifiers are quiet, help relieve congestion and cough symptoms, provide more restful sleep by moisturizing your airways, and can create a more comfortable home environment.

I’m not blinded by their benefits, though, and I’m aware you have to use them the right way to avoid their risks.

Now that I’ve explained how an ultrasonic humidifier works, you can safely buy one and start breathing well-humidified air in your home.


  1. https://www.sciencedirect.com/topics/engineering/bubble-cavitation
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4428615/
  3. https://www.chop.edu/news/vaporizer-or-humidifier-which-best
  4. https://www.mayoclinic.org/diseases-conditions/common-cold/expert-answers/cool-mist-humidifiers/faq-20058199
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Ile Kauppila

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Ile Kauppila
Ile Kauppila is a globetrotting writer and editor living in Virginia. Ile holds an MA degree in Multimedia Journalism and a BA in English Philology. Ile has written for a variety of home, HVAC, and energy-related websites and publications. He has covered HVAC solutions, insulation, and energy-efficient construction, automotive AC systems for multiple auto dealerships and garages.

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