A Detailed Guide: How Do Ultrasonic Humidifiers Work?

how do ultrasonic humidifiers work

Humidifiers can be a great companion in dry environments and can protect you from several skin and health issues.

There are different types of humidifiers ranging from industrial large-scale humidifiers to portable humidifiers, each following its own humidification process to serve the same purpose.

Arguably the most advanced one of all these humidifiers is the ultrasonic humidifier, which uses high-frequency waves to produce a mist that is dispersed into the surrounding air. Let’s take a closer look at how ultrasonic humidifiers work.

What is Humidity?

The main purpose of humidifiers is to add humidity to an environment. Before getting to know about how ultrasonic humidifiers work, let’s first explore what humidity is.

The presence of moisture in our surrounding air is called humidity. With the idea of humidity, a question comes to mind – how does moisture exist in the air? The answer is water vapor. 

Water vapor is the gaseous state of water that is formed when the temperature of water molecules is increased preventing them from retaining their liquid state due to condensation. 

Suppose the weather forecast for your hometown shows that it’s 27°C (80.6°F) outside, which, in theory, would be a pleasant day. However, imagine that for some reason it doesn’t feel pleasant because when you step outside and it feels really hot and sticky, making it difficult to breathe.

Why does it happen? The answer is humidity. A temperature forecast only shows you the dry-bulb temperature. This temperature only takes into consideration the temperature of the air, without including any moisture or radiation that may be present as well. 

Some weather apps have additional features like “real feel” or “feels like”, which account for other factors like humidity.

This example demonstrates how important humidity is in our environment. A lack of humidity can make the air so dry that it starts to irritate your skin and damage your health, whereas excess humidity can quickly create a hot and sticky situation and promote bacterial or mold growth.

Humidification and Dehumidification

Now that we know the importance of humidity, let’s look at the difference between when air is very dry air with low humidity and when air is very damp with extremely high humidity. 

To keep the humidity levels balanced there are two processes known as humidification and dehumidification that allow us to have some control over the humidity level of our surrounding air.

The term humidification means a process of adding moisture to the air in the form of water vapor, whereas dehumidification is the opposite and works to reduce dampness in the air.

Before learning about different types of humidifiers that are available, we need to understand their processes. Humidifiers work in two ways, with cooling and heating methods. 

Humidification with Cooling

Humidification for cultivation of flowers.

Humidification with cooling is a process in which the dry-bulb temperature of the environment is reduced while humidity is increased. 

In this process, air passes through a stream of water that has a temperature lower than the dry-bulb temperature of the surrounding air, which makes the air cooler. The air is then released as the water evaporates and is absorbed into the surrounding air, increasing humidity levels. So this process both cools and dampens the air. 

Cooling humidification can be achieved with desert or evaporative humidifiers which have a water pump that spreads the water around the box and a fan that blows air outside the box. The water circulation inside the box cools down the air and evaporates the water.

Humidification with Heating

The humidification with heating process works in the opposite way to the cooling humidification method. The goal of heated humidification is to increase the room temperature along with the moisture levels and humidity. 

The working principle is the same as the cooling humidification. Still, the difference is that the water that the air passes through is warmer than the dry air temperature of the surrounding environment. During this process, water is evaporated into the air, forming moisture. Since the temperature of this moist air is higher than the dry air temperature, humidity levels are increased. 

A simple DIY way to achieve heated humidification is to put a pot full of water on the stove and let it boil. This will create steam, which will disperse water vapor into the air. Due to the warm temperature of this vapor, the surrounding air will start to get warmer as well as the vapor mixes with the air. 

Other homemade alternatives to humidifiers can include keeping an aquarium or flower vase in your home, as the water in these containers acts as natural humidifiers through evaporation. 

You can also find house plants that can increase moisture through their foliage during plant transpiration.

Dehumidification with Cooling

If you are living in one of the hotter regions of the world, you most likely have experienced days when the humidity levels are high and the air feels sticky and uncomfortable. 

On these humid days, you probably want to reduce the humidity around you, and this can be done with dehumidification. If you go with dehumidification with the cooling process, it would make it even better by controlling both the temperature and the humidity.

This is the most widely used principle for dehumidification, and the split or window air conditioners found in homes work through this process.

In dehumidification with the cooling process, air passes through a cooling coil which is set at temperatures lower than the dry-bulb temperature. This helps to reduce heat along with humidity. As the temperature of air coming out of the system gets lower than the dew point temperature, it can condense the water molecules and turn them from vapor to dew.

Dehumidification with Heating 

Alternatively, you can heat an environment while reducing the moisture with the help of hygroscopic chemicals. Hygroscopic chemicals can absorb moisture while releasing heat. 

During this process, high pressured air is passed through a large vessel enclosed with hygroscopic chemicals. When this air meets the chemicals, the heat is emitted and the moisture is absorbed.

Heated dehumidification is mostly practiced in chemical plants, where the excess moisture can be problematic if it builds up inside the valves and forms dew which can lead to corrosion if not controlled.


Modern Humidifier on Color Background

Devices that can help us regulate the level of humidity in our surroundings are called humidifiers and dehumidifiers.

The primary focus of a humidifier is to increase the moisture content in the air, which is preferred in dry environments since a lack of humidity can cause skin irritation and even health issues. 

A dehumidifier, on the other hand, is a device that helps to lower the humidity by removing moisture from the surrounding air. The air conditioners in our homes are dehumidifiers that help to take the edge off moisture from the air along with cooling temperatures at the same time.

Construction of Ultrasonic Humidifiers

The ultrasonic humidifier is possibly the most technologically advanced kind of humidifier available on the market.  

Before learning the details of its operation, we should look at what is inside an ultrasonic humidifier.

An ultrasonic humidifier consists of the following components:

  • Water reservoir
  • Demineralization cartridge
  • Air circulation fan
  • Piezoelectric transducer
  • Diaphragm
  • Nebulizer chamber

If you open the ultrasonic humidifier the first thing you will see is a small water tank to store the water for the creation of mist. It is recommended to use distilled water since there is a high risk of bacterial contamination due to minerals found in tap water.

At the bottom of the water tank, you will find a small demineralization cartridge. Water contains a few common minerals like calcium, magnesium, sodium, and fluoride and the job of this cartridge is to filter out the mineral contents.

The air circulation fan is also found at the bottom of the humidifier and its job is to circulate the mist created by the piezoelectric transducer’s diaphragm, which is fixed at the bottom of the nebulizer chamber.

How do Ultrasonic Humidifiers Work?

ultrasonic humidifier in the house

Ultrasonic humidifiers work by moving water through high-frequency vibrations to create water vapor. Let’s see how it works in more detail. 

Step-by-Step Process

  1. First, the water from the water reservoir moves down through the demineralization cartridge. This cartridge filters out the dust and water minerals. The important thing to note here is that not every ultrasonic humidifier has this cartridge, so be sure to check if the one you’re purchasing has it or not.
  2. The filtered water then flows through a pipe toward the piezoelectric transducer’s diaphragm. A piezoelectric transducer is a device that utilizes electricity and converts it into high-frequency vibrations.
  3. The frequencies are then followed by the diaphragm vibrating against the water. The diaphragm is a slightly flexible surface that moves in correspondence with the signals received from the transducer.
  4. These vibrations force the water molecules to break into small droplets and the circulation fan then pushes these mist droplets to dissipate in the air passing through the nebulizer chamber.

Working Principle

The ultrasonic vibration of the diaphragm against the water forces water molecules to break into water droplets and form a water mist. The type of droplets and mist may vary depending on the different ultrasonic frequencies.

From experimentation, it is known that a minimum of 2 MHz is required for water mist formation, whereas higher frequencies can create microscopic water droplets for a finer mist. 

An ultrasonic humidifier follows the principles of ultrasonic atomization to create moisture. Ultrasonic atomization is a process that is based on two different effects:

  1. Cavitation bubble implosion: When the speed of vibrations from the piezoelectric transducer increases to an extent where water particles can no longer cling to the part, it leads to the formation of air bubbles due to the compression of water droplets.
  2. Capillary wave theory: After the cavitation, Rayleigh waves are created with the help of a vibrating transducer’s surface. This forces the water droplets to break and dissipate into the surrounding air.

These two phenomena require a minimal amount of energy and can produce a stable mist for long durations. This makes ultrasonic humidifiers stand out among the other types of humidifiers.

Ultrasonic Versus Other Humidifiers

Modern Humidifier on Grey Background

To identify if ultrasonic humidifiers are better than other types of humidifiers, we need to compare and analyze some of their factors and working principles.

Ultrasonic Humidifiers Versus Evaporators

In the workings of both of these humidifiers, their difference lies in how the water vapor is produced. In an evaporator humidifier, water is boiled, turning the water molecules into a gaseous form. This is a type of warm mist humidifier.

An ultrasonic humidifier, on the other hand, uses piezoelectric ceramic discs and lacks a heating element. The current is supplied through a power source via the nickel electrodes. 

The ceramic disc oscillates in the presence of ultrasonic frequency, or ultrasounds, which generates a fine mist through cavitation in the water. As the mist is released into the environment, it generates humidity. This is a type of cold mist humidifier.

Ultrasonic Humidifiers Versus Impeller Humidifiers

Now that we know how an ultrasonic humidifier works, we can compare it to an impeller humidifier. An impeller humidifier cannot dampen your dry home better than an ultrasonic humidifier because an impeller humidifier is much slower due to its use of a spinning impeller.

The impeller has fins attached that carry the water to the reservoir through a screen which eventually breaks up the water molecules into tiny droplets. These droplets swing up in the air and as a result, the humidity increases.

However, an impeller humidifier is one of the least preferred types of humidifier because it doesn’t produce as much moisture as other types, and it tends to be quite noisy. 

Ultrasonic Humidifiers Versus Steam Vaporizers

Steam vaporizers are similar to evaporators in that they release moisture slowly using a heating element. These are widely used in the healthcare sector as nebulizers and can cater to those with flu or cold symptoms. The warmth in the moisture of steam vaporizers can help relieve a stuffy nose or a sore throat.

However, the output from a vaporizer is less than an ultrasonic humidifier. Vaporizers are primarily for small-scale use, which makes them compact but less impactful. 

Ultrasonic Humidifiers Versus Central Humidifiers

In terms of complexity, central humidifiers outshine ultrasonic humidifiers. They are primarily used in large spaces and can better accommodate a much greater area than an ultrasonic humidifier.

However, an ultrasonic humidifier is more energy-efficient and quieter than a central humidifier.

They do have some things in common though. They both have a water supply through a water reservoir, and they both have features inside to help kill harmful bacteria (UV light, etc). Filters are incorporated into all humidifiers to trap sediments and residues that might be harmful.

All humidifiers require care and cleanliness to extend the product life.

Benefits of Ultrasonic Humidifiers

Using an ultrasonic humidifier can give you a few benefits over other humidifiers:


Ultrasonic humidifiers are the safest kind of humidifier because they do not use any hot water like other evaporative models, avoiding the risks of spillage and burns.

Ultrasonic humidifiers are often preferred for bedrooms to create a safe space for everyone, especially kids and pets.

Cheaper Operation

Buying an ultrasonic humidifier might be slightly more expensive than other humidifiers, but it is a one-time investment that will keep you comfortable in the long run because the cost of operation for these humidifiers is much lower than the others.

Ultrasonic humidifiers also use the least amount of energy to operate compared to other humidifiers because they do not require heating the water or running a fan to produce water vapor.

The ultrasonic humidifier’s piezoelectric transducer helps with the creation of moisture and it consumes a small amount of energy compared to other mechanical humidifiers.

Along with the low energy requirement, ultrasonic humidifiers do not require any sort of filter to be cleaned or replaced regularly. A demineralization cartridge does the cleaning job for this humidifier.

Less Noise

Since there are not many mechanical processes involved in ultrasonic humidifiers, they are extremely quiet machines. 

Final Words

An ultrasonic humidifier can be a great addition to your home if you’re looking to create a favorable environment. Without consuming much energy, these humidifiers help you to overcome dry air by releasing moisture and increasing the humidity without making much noise.

The next time you shop for humidifiers you can now easily determine what type of humidifier you need, and how it works.

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