Why Does Your Humidifier Smell Bad And How To Fix It?

Having a humidifier is great for improving humidity levels and making you feel comfortable, especially in arid regions or during the winter months. However, it can cause some issues at some point. For example, many people will complain about the foul smell coming out of it. 

A humidifier can smell musty or smell like pee. There are various odors that people may come across and have to deal with while using a humidifier. But the main culprits are always the mold and mineral deposits. 

In this post, I will analyze the causes of humidifier smells and teach you how to address them properly. Smells can be dangerous for your home and overall health. Therefore, you should fix it as soon as possible.

Why does my humidifier smell?

It is hard to give a single cut-edge answer to this question. There are a few causes that can make your humidifier smell bad. Without further ado, let’s dive in.

Humidifier smells musty

Molds have a strong musty or earthy smell. When you detect that your humidifier smells musty, there are likely too many molds in the water tank or other hidden places. 

Molds thrive in humid environments, and the water reservoir is the best place for it. If you don’t replace the water in it regularly, the stagnant water will become a breeding ground for molds and bacteria. 

mold in humidifier

While a large proportion of them can be killed when using a warm mist humidifier, they will go into the air with vapor if you are using a cool-mist unit. 

These molds can pollute the air and be inhaled into our bodies eventually. The increased mold spores in the air can cause allergic symptoms such as a runny nose and difficulty breathing. It could even lead to severe illnesses such as lung infections. 

Humidifier smells like pee

Sometimes, your humidifier can produce a mist that smells like urine, which is disgusting. This is due to the mineral deposits accumulated in the tank. 

Not everyone will choose to use distilled water even though most manufacturers recommend it. When they fill the tank with tap water, the minerals will settle down in the tank and become buildup. 

These deposits often consist of calcium, potassium, sulfur, and magnesium, which can cause a urine smell when they are kept in the water for a long time.

Humidifier smells like a wet dog

It is hard to describe this smell accurately. Anyway, it is a complex smell we want to avoid. Actually, the scent of wet dog doesn’t come from the dog itself; instead, it originates from the yeast and bacteria in its fur.

So when some specific yeast and bacteria species grow in your humidifier’s tank, it will release a smell like a wet dog as well. 

Humidifier smells like plastic

It often happens in newly bought humidifiers. The humidifier is usually made of plastic, containing some smells that need to be released gradually. 

These smells could be strong initially but will gradually reduce with use. Typically, the smell will disappear after a few usages. 

If the appliance continues to smell bad, there is something wrong with the material. Don’t let the material pose any risk to your health since it may contain many harmful chemicals. You should send it back if possible.

Humidifier smells like burning

A burning smell could be a sign of overheating or failing the humidifier’s electrical components. It could even catch fire if you don’t treat it properly. 

I suggest you unplug it immediately and check the conditions of these electrical components one by one. Sometimes, it can go back to normal after a while. Otherwise, you should go to an electrician or purchase a new unit. 

Humidifier smells like vinegar

A 1:3 solution of water to vinegar is excellent for cleaning a humidifier, but it is not a good idea to leave it in the tank and let it evaporate with the mist. 

If your humidifier smells like vinegar, it is due to the fact that there is too much vinegar left in the tank. Vinegar can cause corrosion of electrical components and irritate your eyes and nasal passages.

How to make a humidifier smell good?

how to make humidifier smell good

Having a humidifier that smells bad is annoying. Luckily, you can remove the unpleasant odor quite easily. I list out a few ways to make your humidifier smell good in this section.

Clean it thoroughly

When it comes to humidifiers, the importance of cleanliness can’t be overstated. The water tank is a natural site of mold or mildew growth since the water in it is stagnant to some extent.

It will also accumulate mineral deposits if you don’t use distilled water. These buildups could cause the humidifier to stop producing mist.

You should clean your humidifier at least once per week. To kill the bacteria and mold, you should add vinegar or other cleaning agents to the tank and mix it with water. Then let it sit for at least half an hour to let the solution take effect.

You may also need a toothbrush to scrape off the mineral buildup stick to the inside wall.

Replace the filter

Occasionally, the smell doesn’t disappear even after a thorough cleaning. If you have a filtered model, it is time for you to clean or replace the filter. 

Many manufacturers suggest you replace it every three months, but a filter may not last so long if you use it frequently or live in an area with hard water. The filter allows the microorganisms to survive and thrive, constantly releasing bad smells. 

Humidifier filters often come with a low price tag, which won’t burden you.

Changing out the water after each use

Many people like to keep the remaining water when they refill the tank, meaning that a portion of stagnant water will always be held in the tank. 

The stagnant water contains molds and bacteria. When clean water is mixed with it, these microorganisms will breed and thrive continually, and you can never get rid of the bad smell.

Therefore, you should change out the water after each use and keep the tank dry when not in use. 

Use distilled water 

If you struggle to commit to regular cleanings, choosing a warm mist humidifier or filling it with distilled water would be a better solution. Distilled water is free of minerals, so there are few scales left.

Note that distilled water could be costly, but you can make it at home.


A humidifier can have a bad smell over time. The molds can make it smell musty, and the mineral deposit can create a smell like pee. There are various smells, and most of them come from stagnant water. 

To make your humidifier smell good, you should clean it regularly and replace the filter from time to time. Distilled water can significantly reduce impurities, and changing out the water is a must to prevent molds and bacteria. 

A bad smell is always a sign of health risk. It is time to identify the problem and remove it!

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested a lot of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.

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