How Do Humidifiers Work? Everything You Wanted To Know

In this quick guide, we’ll be explaining how humidifiers work.

Humidifiers are a popular home appliance that help you increase the humidity in a room or other indoor space. There are a couple different mechanisms and components that allow humidifiers to do what they do.

But before we get into how modern humidifiers work, we have to explain a concept known as ‘relative humidity’. We’ll also get into the ‘why’, ‘when’ and the ‘where’ of humidifiers, to help you understand how they work.

Put simply, a humidifier increases the ‘relative humidity’ of a room. The reasons why you might want to do so range from those related to comfort, to those concerned with health and physical well-being.

We review humidifiers professionally, so if you were confused about how humidifiers work, you came to the right place.

Now, let’s jump right into how humidifiers work.

Humidity and Relative Humidity

So what exactly is humidity?

‘Humidity’ is the amount of water in the air. That’s it. 

More accurately, humidity is the amount of water vapor in the atmosphere. If you’re familiar with that ‘wet’ warmth on a hot summer day, you know what high humidity is. That feeling of ‘wet warmth’ comes from there being a larger amount of water vapor in the atmosphere.

Low humidity on the other hand, is when the water vapor content of the atmosphere is low. You’ll have experienced low humidity on very cold days, when the air just seems ‘dry’. Or if you’ve ever been in an area that hasn’t seen rain in ages, even hot days can have low humidity. 

Humidity and Temperature

Ambient temperature affects humidity. A given amount of air is capable of holding a certain amount of water vapor. When it gets hotter, the air can hold more water vapor and vice versa. 

This is where ‘relative humidity’ comes in. If the relative humidity of a location is lower, that means the air is dry and capable of holding more water vapor at that temperature. 

At around 20 C (68 F), 1m3 of air is capable of holding upto 18 ml of water. When the temperature increases to 25 C (77 F), the air is capable of holding upto 22 ml of water. 

If the temperature increases to 25 C (77 degrees F), and each cubic meter of air is holding 22 ml of water, we say that the relative humidity is 100%. Similarly, if the temperature is 25 C (77 F), but each cubic meter of air is holding 11 ml of water, we say that the relative humidity is 50%. 

If you’ve ever used a weather app, the percentage displayed in the ‘Humidity’ section is actually ‘relative humidity’. 

Why Relative Humidity Matters

The relative humidity of a location, be it an open space, an office building, or a bedroom makes a huge difference in how comfortable you are. Imagine going for a jog when it’s nice out, vs. going for a jog in the dead of winter. Odds are you feel your throat getting dry in the winter. 

This is because colder temperatures mean less water vapor in the air, which results in dry throat. But the effects of low relative humidity extend further than that. 

It’s easy for enclosed spaces such as office buildings, classrooms, and bedrooms to experience low relative humidity. If you’re sitting at your desk at work, the lower relative humidity might cause your throat to become dry, which could cause you to start coughing. 

If you notice your skin becoming dry or cracking in the winter, low relative humidity is to blame. The same goes for cracked/chapped lips, itchy noses, and dry hair. 

Our least favorite consequence of low relative humidity is the buildup of static electricity in household objects, where every door handle is out to electrocute you! 

Prolonged exposure to low humidity can cause problems around the house too. These include warping of wood panels and floors, peeling of wallpaper at the edges, and doors not sealing as well as usual. 

How Low Is Too Low?

Generally speaking, people are most comfortable at a relative humidity of 40%. 

The relative humidity of a house can drop to as low as 10%. To put that into perspective, the average relative humidity of the Sahara Desert is around 25%. If you want to get an accurate measurement for the humidity in your house, a hygrometer is a device that does just that. 

And low relative humidity isn’t just a problem for cold weather. In fact, it can be a problem even in warmer weather. 

How To Deal With Low Relative Humidity

Low humidity can be a real pain. Thankfully, there are a couple things you can do to boost humidity.  

Leave The Door Open After Showering

This is a popular method of increasing the humidity of a room. When you shower, the excess water stays suspended in the air for a while. By leaving the door open, you let some of that humidity into the room, increasing humidity. 

While easy to do and completely free, this method isn’t exactly practical as the effect is short-lived.

Cook or Boil Water Without A Lid

When you boil water, or cook, a lot of water evaporates into the atmosphere, where it works to increase humidity. But again, this method is only effective for a short while.

Not to mention, you could rack up a hefty power bill if you run your stove constantly. 

Keep House Plants

An interesting way to boost humidity is to keep houseplants, which boost relative humidity around the house via ‘evapotranspiration’, the movement of water from the soil to the top of leaves, where it is evaporated. 

The only drawback is having to care for the plants. They will need regular upkeep and maintenance which is a hassle. 

Use A Humidifier

And finally, we have the most effective option: using a humidifier. Humidifiers come in all shapes and sizes, from large setups that integrate right into your house’s central heating system, to small devices you can put on a nightstand. 

Humidifiers are cheap and can be found at just about any price point. They are readily available at most stores and online, and the only real maintenance they require is refilling with water and the occasional filter change. 

They’re really effective too. Even the smallest humidifier can easily cover and boost the humidity of an entire room. Larger ones can be used in more expansive spaces such as living rooms. 

Humidifiers also come with plenty of really useful features. You can adjust the amount of humidification, the direction you want the mist to go, set timers to turn the humidifier off, and so much more. 

How Humidifiers Work

So now that we’ve concluded that humidifiers are your best bet for combatting low humidity, let’s talk about the design and mechanisms that make it possible. 

Most consumer humidifiers are pretty simple. You have a tank that holds the water, some kind of mechanism that converts the water from liquid to water vapor, and a fan that directs the mist where you want it to go. 

Types Of Humidifiers

There are a couple different types of humidifiers, each of which works slightly differently. 

Evaporative Humidifiers

This type of humidifier directs water onto a wicking filter, which has air blown on it by a high speed fan. The air causes the water to evaporate, and it is then directed out into the atmosphere. 

Ultrasonic Humidifiers

This is another common type of humidifier that uses a vibrating plate or probe that oscillates at high, ultrasonic frequencies, thus the name. The vibrating actually causes water to convert into a mist of fine droplets, which are then released into the atmosphere. 

Ultrasonic humidifiers are ideal if you want to sleep with a humidifier on, as they produce the least noise, running almost completely silent. Another advantage is that the mist from these humidifiers tends to be cool and pleasant. 


With impellers, a rotating component throws water at a diffuser. The shape of this diffuser often resembles a comb. It’s the diffuser’s job to break up the water into finer droplets which then make their way into the atmosphere. 

Impellers humidifiers (and ultrasonic ones too) require more frequent cleaning. This is because the water can become stagnant, allowing bacteria to thrive. This bacteria-ridden water, when released into the air, could pose a lot of health concerns. 

That said, regular cleaning rectifies this problem. 

Steam Humidifiers 

Steam humidifiers (also known as vaporizers) boil water using a heating element and eject warm steam into the surrounding area. These are some of the cheapest humidifiers you can buy and can even be used with medicated inhalants. 

The drawback is that they are less energy efficient than most other humidifier types. Because they use a heating element, they can also cause burns if mishandled. 


So there you have it folks. That’s a quick look at how humidifiers work. Here, we learned what relative humidity is, why it’s important, and the different ways to boost low relative humidity. And while there are a number of methods to try, by far the most effective and convenient one is to use a high quality humidifier. 

If you aren’t sure which humidifier to get, we’ve got you covered. Check out our reviews and recommendations, where we give you our thoughts on the best humidifiers for your particular needs.


Shawn Willis is all about humidifiers. After working for some of the biggest names in the industry, he started HumidifierGuys with Scott Dawson. Now, the dynamic duo helps others figure out what they need in their next humidifier.

Shawn is an avid sports fan, motorcycle enthusiast, and has two dogs named Whiskey and Boba.