How to Clean Mold Out of Your Humidifier

This is our step-by-step guide on how to clean mold out of your humidifier. 

If you use a humidifier regularly, mold can be a real problem. Humidifiers that use hard water are especially susceptible to mold, though it can also develop if you haven’t been keeping up with the maintenance. 

Mold in your humidifier’s water tank decreases the efficiency of the unit, but it also poses a serious health risk if it is released into the air that surrounds you. 

Thankfully, it is pretty easy to clean, and there are a couple different methods you can try. 

We’ve had to deal with mold in a humidifier lots of times, and we’d love to share some tips for cleaning it with you. 

So without further ado, let’s discuss how to clean mold out of a humidifier. 

What Causes Mold In Humidifiers?

Humidifiers can develop mold for any number of reasons. The most common culprit is hard water. If you aren’t familiar, hard water is water that has a very high mineral content. If you live at high elevation, it’s possible you get hard water from your tap. 

The high mineral content of hard water can deposit in the water tank of your humidifier, where it can allow mold to develop. 

Another likely reason for mold in humidifiers is just lack of proper cleaning. Humidifiers need to be cleaned regularly and thoroughly in order to preserve performance and avoid mold. 

If you aren’t keeping up with the cleaning and maintenance, or if you haven’t replaced the filter in a while, it’s easy for mold to develop in the humidifier.

Why Mold In A Humidifier Is Bad

There are a couple different risks involved with leaving mold in your humidifier. For one, it severely impacts the performance of your humidifier. You might notice the humidifier doesn’t work as well, or that some parts start malfunctioning. 

More than that, there are health risks associated with mold in a humidifier. It is easy for mold from the water tank to be released into the surrounding air. Here, it can cause various health issues, most commonly breathing and respiratory problems. Coughing, sneezing, breathlessness, and wheezing are just a few symptoms. 

You may even experience serious allergic reactions, itching, watery eyes, headaches, and a variety of other health problems. 

What You’ll Need To Clean Mold Out Of A Humidifier

So now that we’ve established that mold in a humidifier is bad news, let’s discuss the most effective methods for dealing with it; starting with what you’ll need. 

Mold Cleaning Checklist

There are a couple different ways to clean mold out of a humidifier. The first one will require the following: 

– Distilled water

– 3% hydrogen peroxide

– Rubber gloves

– A face mask

– Goggles or other eye protection

– Dish soap

– A sponge

– A stiff bristle brush

If you go with the second method, you’ll need all the same supplies as Method 1, except for the hydrogen peroxide. Instead, you will use distilled white vinegar. 

So now that you’ve got all the gear and supplies at the ready, let’s get into how you clean mold out of a humidifier. 

How To Clean Mold Out Of A Humidifier

Step 1: Identifying Mold

The first step is to identify where exactly the mold is and how severe it is. Before you even think of touching a humidifier that you suspect has mold in it, we highly recommend wearing protective gear. That may sound like overkill, but it never hurts to be too safe. 

So put on your rubber gloves, goggles, face mask, and any other protective gear you might have. You should keep these on throughout the cleaning process. 

Now, inspect the humidifier unit. Mold usually develops in the water tank, so start there. If you don’t find any mold in the tank, the nozzle and filter also tend to be hot spots for mold. 

If you don’t know what to look for, mold usually appears in the form of a ‘furry’ growth, black stains, or even specks that range from greenish browns to orange in color. 

Step 2: Pour The Cleaning Solution Into The Tank and The Humidifier 

Next, it’s time to make our cleaning solution. You do so by pouring 4 parts distilled water and 1 part hydrogen peroxide into the tank.  

Note: If you are using distilled white vinegar instead of hydrogen peroxide, the ratio of the cleaning solution changes to 1 part distilled water and 1 part distilled white vinegar. All other steps stay the same. 

Many folks ask why we recommend using distilled water instead of purified water or even tap water. 

Distilled water is best for cleaning mold as it is completely free of any contaminants, minerals, and even heavy metals. Purified water, on the other hand, is quite mineral rich. While unlikely, this mineral content could actually exacerbate the problem. Therefore, it is best to use distilled water. 

Step 3: Shake The Tank Well And Leave It For A While

Once you’ve poured the cleaning solution into the tank, close the tank and shake it vigorously. After that, you’ll want to leave it sitting for at least an hour. 

After it’s been sitting for at least an hour, empty the tank and thoroughly rinse the whole thing with distilled water. We urge you to dispose of the mold-ridden water safely and responsibly. 

Now, if there is still a bit of mold stuck to the inside of the tank, we recommend pouring a bit more of the cleaning solution on it and agitating the mold with a bristle brush. You may have to do multiple passes, but this should remove any remaining mold. 

Step 4: Clean The Unit With Dish Soap

This might seem like overkill again, but it’s worth the extra effort. After you’re done cleaning the mold out of the humidifier, we highly recommend cleaning it again with dish soap and a sponge. Dish soap might not be recommended for cleaning some models of humidifier tanks, but most should be fine. 

Doing a second clean with dish soap and a sponge ensures that there are no leftover bits of mold or any other contaminants in the tank. 

How To Prevent Mold In A Humidifier

Cleaning mold out of a humidifier can be really time consuming, if you’re doing it properly. You also run the risk of exposure to the mold if you aren’t careful. Thankfully, there are a few things you can do to prevent mold from developing in your humidifier in the first place. 

Use Distilled Water In Your Humidifier

If you want to avoid your humidifier’s water tank developing mold, we highly recommend using distilled water. While both distilled water and purified water are safe to use in a humidifier, purified water is still quite mineral rich, so chances of developing mold are higher. 

Hard water should be avoided at all costs, and if your tap gets hard water, consider switching to distilled water, or at the very least purified water.  

Empty The Tank 

If you aren’t using the humidifier that often, it is mandatory that you empty the tank and dry it using a towel in between uses. This eliminates the risk of the water becoming still, which can cause a variety of issues, including mold. 

Still water could become a breeding ground for mold, bacteria, and other disease-causing microbes. 

Emptying the tank means you won’t have to deal with any of these problems. 

Keep Up With Your Humidifier’s Maintenance 

One of the best ways to avoid mold in a humidifier is to keep up with the maintenance of your humidifier. That means replacing the filter at the manufacturer-recommended intervals. This will also ensure consistent high performance of your unit. 

Maintenance also includes regular cleaning of the water tank, the nozzle, and any other parts of the humidifier than come in contact with water. 

How Often Should You Clean Your Humidifier?

Besides keeping your humidifier mold-free, regular cleaning also helps it perform better. But  just how regularly should you clean your humidifier? 

Well, the answer to that really depends on the type of humidifier you have, how often it gets used, what settings you use it at, and even the capacity. Generally speaking, it is always recommended that you clean your humidifier at least once a week. 

However, if the unit gets used more often, as in the case of humidifiers that run while you sleep, even more frequent cleaning may be required. It all depends. 

A good rule of thumb is to follow the manufacturer-recommended cleaning protocols. This should tell you how often you need to clean the humidifier with normal usage, and then you can adjust, based on how much more or less you use the humidifier.


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.