Can A Humidifier Cause Mold?

This article discusses mold caused by a humidifier. 

Mold in a humidifier is a common, yet highly concerning problem.

It is most often seen on humidifiers that use hard water, i.e water that is very rich in minerals, heavy metals, and other such contaminants. 

If you use your humidifier regularly, it is important to keep up with the maintenance and cleaning. Failure to do so could result in mineral deposits, and even mold. 

Here, we will talk about how exactly mold forms, what the risks are, and also tell you how to deal with mold caused by a humidifier. 

Keep reading for more information.

What Exactly Is Mold

If you aren’t familiar, mold is a fungal growth that thrives in damp and humid conditions. Visually, it looks like a furry growth made up of strands of fungus. The color of mold varies. 

It is usually brown, gray, or even black. That said, it could even be pink, orange, green, blue, or any combination of the above, depending on where it forms and the ambient conditions. 

Can A Humidifier Cause Mold?

Mold usually develops in very humid, damp conditions. It is also possible for mold to develop in humidifier water tanks that are exposed to a lot of hard water, or other contaminants. 

Besides the water tank, mold can also affect the filter or nozzle of your humidifier. 

While in the humidifier, mold will cause the unit to perform poorly. You may notice that the mist volume is lower, or that the humidifier has a hard time diffusing water. 

The real problem starts when that mold travels through the humidifier and into the surrounding air. Here, it can settle on furniture, and anything else. 

Why Mold Is Bad

There are a number of health concerns and risks associated with mold. If humans come in contact with mold, they can become very sick. Symptoms that might point to mold include coughing, sneezing, skin irritation and rashes, itching, allergic reactions, watery eyes, and headaches. 

More extreme symptoms include respiratory problems such as breathlessness and asthma, lung irritation, and the like. 

Mold also affects your house and surroundings. It can grow on walls, ruining the paint or wallpaper. It can rot wooden floors, fixtures, and other furniture. Food left out in the open is also very susceptible to mold. 

Keeping all of that in mind, it is essential that you address mold as early as you can to prevent it from spreading and causing problems. 

Why A Humidifier Might Cause Mold

There are a couple different reasons your humidifier might have developed mold. 

Hard/Mineral-Rich Water

If you use hard water, i.e water with a very high mineral content, it increases the chances of your humidifier developing mold. The minerals and other contaminants in the water can cause mold or bacterial growths to thrive in your humidifier. 

Lack Of Regular Cleaning

Another common reason for mold development in a humidifier is just a dirty humidifier. If you want your humidifier to perform well and last longer, regular cleaning is a must. A dirty water tank, or nozzle can easily become a breeding ground for mold. 

Old Water Filter

If you haven’t cleaned or replaced the water filter in your humidifier, it could be the reason your unit is moldy. The water filter’s job is to collect dust, irritants, microbes, and other contaminants in the water. 

If you haven’t replaced the filter in a while, it is possible that it is not filtering the water as effectively. This could cause contaminants to stay in the humidifier for longer. These contaminants can deposit in the tank, the nozzle, or anywhere else and allow mold to develop. 

How To Prevent Mold In A Humidifier

Mold in a humidifier can have disastrous effects on your health and your surroundings. So what can you do to prevent it from developing in the first place? 

Here are some measures you can try: 

Use Distilled Water

Distilled water is water that does not contain any contaminants, minerals, or heavy metals, all of which can promote mold growth. Compare that to purified water, which is free of all contaminants, but still retains the minerals. Distilled water is by far the best and safest choice for use in humidifiers. 

We highly recommend using distilled water in humidifiers, even if they aren’t experiencing mold. Using distilled water in humidifiers has many benefits, in addition to lowering the chances of mold. 

Keep in mind that distilled water will cost you a bit more than purified water or tap water. Still, it’s definitely worth it. 

Keep Up With Regular Cleaning 

One possible reason your humidifier could be experiencing mold is because you haven’t been keeping up with the cleaning. We recommend humidifiers be cleaned at least once a week with regular usage. 

If you use it more often or at higher mist settings, the need for even more frequent cleaning arises. You should clean the water tank with a cleaning solution that effectively removes contaminants. 

Disinfection of the water tank is also a good idea, and should be done at least once a month. 

Replace The Filter 

If your humidifier uses a water filter, it is essential that you replace it periodically. The exact time interval between filter replacement will again depend on how often your humidifier gets used, and how hard.

Still, even moderately used humidifiers could do with a filter replacement every 2 or 3 months. Make sure to get the manufacturer recommended filter for optimum performance and longevity. 

How To Clean Mold Out Of A Humidifier

Before we tell you how to clean mold out of a humidifier, we must stress the need to wear proper personal protection gear. At the very least you should be wearing rubber gloves, a face mask, and goggles. 

Now that you’re ready, let’s discuss how to clean mold out of a humidifier. We recommend using a cleaning solution made by mixing one part 3% hydrogen peroxide with 3 parts distilled water. Alternatively, you could use a cleaning solution made by mixing distilled white vinegar and distilled water in equal parts. 

Note: A good way to prevent mold from developing in your humidifier is regular cleaning, followed by disinfection. You can use either of the solutions we have recommended to disinfect a humidifier after regular cleaning, even if it doesn’t have mold. 

Pour the cleaning solution into the tank. Close the tank and shake it thoroughly, allowing the cleaning solution to cover the entire affected surface. Shaking the humidifier also helps loosen a lot of the contaminants in the tank. 

Next, let the tank sit for a while; we recommend no less than one hour. 

Once the hour is up, pour out the cleaning solution and finish off with a regular clean using distilled water and dish soap of your choice. 

You might notice some mold or other contaminants that refuse to budge. Here, a hard bristle brush and cleaning solution will make short work of even the most stubborn mold. 


Mold in a humidifier is a common problem. There are various reasons for it, from a neglected water tank that doesn’t get cleaned, to a filter that needs replacing, or even just the type of water being used. 

It is essential that you do everything you can to prevent mold from developing in a humidifier, as mold has disastrous effects on both you and your house’s health!

There are a couple ways to prevent mold, such as using distilled water, cleaning the unit regularly, and replacing the filter when needed. 

And if all else fails, a thorough clean with a special solution should take care of your mold problem.


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.