Why Does My Humidifier Smell Musty?

A high-quality humidifier is an asset to have in your home! The device comes in handy with the dry air problem in winter by producing additional moisture in your indoor.

Health-wise, a humidifier is perfect for those suffering from dry skin and sinuses, and it also lessens the risks of catching a cold or flu by moisturizing the air.   

However, a humidifier does not last forever without fixing it at least once or twice throughout its usage. In addition, the humidifier often develops a smell if not cleaned properly from time to time. So if your device is giving off an unpleasant odor, do not worry!

 This article will discuss how to get rid of musty smells from a humidifier and make it clean.

Why does Humidifier Smells Musty?

Stagnant water is the root cause of all musty smells. When water sits in a humidifier for an extended period, it becomes stale and provides a good breeding ground for bacteria. This mold will develop on any surface with excess moisture, including inside the humidifier.

Why Your Humidifier Smelling is a Problem

A humidifier is not designed to run all the time, and they are usually turned off when not needed. As discussed above, one of the most common causes behind musty smells is mold growth inside the stagnant water.

The stale water in your humidifier can be problematic if you breathe that air for an extended period. Below are several problems that tag along with a musty smell humidifier. 


A smelling humidifier means an uncomfortable home, and the stale, musty odors released in the air create a discomforting environment. Additionally, the smell is unpleasant, but it can also cause health problems for the user and their families. 


People with respiratory conditions such as asthma and allergies are more prone to these musty smells in humidifiers. The mold spores that gather inside increase their risk of getting ill, and they also worsen the condition if they already have one. 

People with allergies like pollen, dust, and pet fur are sensitive to musty smells. If you have such allergies, it is best to turn off the humidifier with a musty smell.


A musty smell caused by bacteria and mold can cause respiratory problems such as bronchitis, sinus infections, and pneumonia. It is crucial to clean your humidifiers often to avoid risks of any illness that may affect you.

Body Aches

If there is a musty smell in your humidifier, it can cause body aches. The air you breathe is filled with stale water, bacteria, and dust. The bacteria and mold spores that gather inside the device spread around when turned on. This causes headaches and fatigue due to a lack of good air quality. 

Reasons your Humidifier Smells Musty

There are several reasons behind a musty smell in your humidifier. The most common reasons for this problem are listed below:

Mold and Mildew Build up in the Humidifier

Mold is a fungus that develops on any surface with excess moisture. The humidifier absorbs the water and provides a comfortable environment for mold to grow, and mold also grows in dark areas, including inside the humidifier. 

Mildew also forms with time, and it is a form of mold. This occurs when the humidity inside the humidifier rises past 70%. When you keep the device running for long, it becomes an ideal home for molds and mildew, thus the musty smells in the humidifier.

Dirty Filters

Filters are a must-have accessory for your humidifier. The filters keep the water clean and provide moisture to the air. However, it is essential to change or clean them once every few months as they become dirty over time. 

The dirt is from filtered impurities from tap water and minerals from the reservoir’s surface. If you do not regularly replace or clean these filters, mold starts growing inside. Over time, you might begin to notice a musty smell coming from the humidifier.

Evaporator Belt Failure

The evaporator belt is a rubber band that connects the motor and fan. Over time, this part gets worn out due to use. The fan stops working when the belt wears down, and the humidifier does not work efficiently. 

The humidifier may start to smell musty when the evaporator belt fails, and this is because air does not move through the device, and water starts gathering in different parts of the machine.

Stagnant Water Inside Humidifier

When the evaporator belt fails, it does not turn to rotate the water inside, and this causes stagnant water that gathers into one corner of the humidifier or at places where there is no filter or drain system. 

Additionally, water in the reserve tank also stagnates and turns dirty. The stagnant water provides an ideal environment for bacteria and mold to form. This water eventually festers, leading to a musty smell in your humidifier.

Incorrect Humidifier Size for Your Room

It is important to determine which size suits your home before getting one for yourself. The size of your room affects the humidifier that you use. If you choose a large capacity humidifier for a small space, the machine will produce too much humidity inside the room and the humidifier. 

Excess humidity in the device, in turn, promotes the growth of mold and mildew, and this leads to a musty smell in the humidifier.

How Do You Get the Musty Smell Out of a Humidifier?

If you notice a musty smell in your humidifier, then it means it is time you need to clean the device. Regular cleaning and maintaining the humidifier ensures no bacteria or mold growth inside, and this will help you prevent a musty smell from developing inside the humidifier.

 Additionally, it would help if you considered using a cleaning solution to clean it up entirely and prevent any foul odor from sticking around for long.

What to Put in Humidifier to Prevent Mold?

You can put several things into the humidifier to prevent mold formation. These include household items such as;

White Vinegar; White vinegar is an excellent mold-breaker and prevents the growth of molds, mildew, and bacteria in your humidifier. Add one cup of vinegar to the water inside the reservoir tank, and run it for an hour. 

Tea Tree Oil; Tea tree oil is another compelling element that prevents bacteria and mold growth. Add a few drops of tea tree oil to the water in your humidifier and leave it overnight. It can also aid in breathing for those suffering from asthma, cold, and flu.

Hydrogen Peroxide; This is another powerful antibacterial element that can prevent mold and mildew formation inside the humidifier. Add half a teaspoon of hydrogen peroxide to the water inside your humidifier and leave it on overnight. 

Essential Oils; Essential oils like lavender, eucalyptus oil, peppermint oil, and lemongrass are antibacterial elements that prevent the growth of bacteria in your humidifier. Add a few drops of water inside the reservoir tank and run your humidifier for a few hours.

Humidifier tablets; The tablets are found in your local supermarket or grocery store. They are specially made to prevent mold growth in humidifiers when added to water during cleaning cycles.

Can Mold in a Humidifier Make you Sick?

Yes, mold in a humidifier can make you sick hence the need for a mold free humidifier. This is because the mold particles float around in the air when the humidifier is on. Mold is not healthy for humans because it can cause allergies or respiratory problems such as asthma attacks. 

If anyone inhales this mold, it may lead to respiratory infections like pneumonia, cold, or flu. Additional effects of mold inhalation include headaches, fatigue, coughing, and wheezing.

How Do I Know If My Humidifier Has Mold?

Telling if your humidifier has mold is not easy. However, you might check out for the following signs;

  • You may start noticing a slight musty smell after some time if the humidifier does have any molds or mildews in it. 
  • You might notice a slight discoloration of the water in your humidifier. This happens when mold starts to grow and spread inside it. 
  • Discoloration on the water tank or parts of your humidifier is another sign that you need to look at. You will see black spots or patches on the water tank walls.
  • Check for the filters of the device. If the filters are covered with black or brown spots, it can indicate that mold has started to develop inside your humidifier.
  • You should also check if there is any debris inside it, as this can be a possible indication that you have molds in your humidifier.

How Often Should Humidifiers Be Cleaned?

Regular cleaning of the humidifier is necessary to prevent the growth of mold and mildew inside it. It would help if you cleaned the device weekly or after every two weeks depending on how much you use it and where you place it in your house. 

This will help ensure that all the dirt, debris, and other substances do not settle inside the device’s reservoir tank. Additionally, this will prevent the foul odor from developing inside it.

How to Clean a Humidifier with Mold

Cleaning your humidifier is an essential part of its maintenance. The device needs to be cleaned often to avoid the risk of getting sick from dust, bacteria, and mold that form inside it. In addition, cleaning weekly might be recommended for people who suffer from allergies and other respiratory conditions. 

On average, cleaning your humidifier with mold requires around 30 minutes. However, before kicking off the washing process, it is best to read the user manual that came with the device. 

You will also require the following materials for the process:

  • Distilled white vinegar,
  • Liquid chlorine bleach,
  • Cleaning cloth/soft toothbrush. 

Follow the below steps to clean your humidifier:

Step 1. Unplug and empty water

Unplug all electrical wires connected to the device before starting the cleaning process. Next, open up all humidifier parts, including filters, evaporator belt, fan cover, and other accessories. 

Please turn off the water supply and empty any remaining water present in it. You can use a towel or sponge for this purpose, depending on the size of your humidifier.

Step 2. Clean the base and the tank

Add a cup of chlorine bleach to the water in a container, then add about two cups of distilled white vinegar into it. Mix thoroughly until both liquid contents dissolve well in the water. Pour the mixture into the water tank of your humidifier and leave it for 10-15 minutes.

This will allow the cleaning solution to work through the tank and base and loosen stiff stains. Swish it around to clean the inside of the tank and empty it.

Step 3. Clean other parts of the humidifier

You will need to clean other humidifier parts with a cleaning cloth or toothbrush. Please get rid of any dirt, dust, and mold accumulated inside it over time. 

Dip the cloth in a white vinegar solution, wipe down the fan blades, evaporator belt, and other accessories. Scrub each part thoroughly, rinse them in warm water, and air dry before placing them back into the device. 

Step 4. Reassemble back the humidifier

Reassemble back the parts of your device after they are completely dry. Next, plug in all electrical wires, turn on the water supply, and fill the humidifier tank with clean water.

Step 5. Turn on the humidifier and check for leaks

Please turn on your device, then place it in its desired use location. Check for leakages or spills around the unit’s base while running to ensure that all parts are correctly sealed together again. 


Humidifiers are a great way to help you overcome a dry winter. However, these devices can become breeding grounds for bacteria and mold if not cleaned regularly with the proper cleaning methods.

It is best to clean your humidifier weekly or after every two weeks depending upon usage levels, to prevent any of this from developing inside it. Additionally, maintaining the device will prevent any foul odor from developing inside it.

Cleaning your humidifier with mold is not very difficult. With the right cleaning supplies, you can quickly disinfect and clean your device every few days, depending upon the frequency of usage. You can follow the above steps to clean your humidifier.