Why Does My Air Conditioner Smell Like Pee & What To Do?

Air conditioners can be a godsend on hot summer days, but the air they produce isn’t always as clean as you’d expect. Your air conditioner may occasionally smell like pee.

Don’t be too concerned! The urine smell in your AC often comes from the byproducts of mold and bacteria, and you can remove it by cleaning the filter, coils, and ducts.

In this post, I will walk you through the most common causes of urine smell in an air conditioner and teach you how to remove and prevent the smell from returning.

There is a lot of useful information to know and let’s get started right now!

Is it true that there is pee in my air conditioner?

Many people are disgusted when they discover a pee-like odor in their air conditioners because they believe their appliances have been contaminated by real pee.

Has anyone peed in your AC? It is likely not. Pee is not the only thing that can produce a urine smell. As long as something contains some specific substance, it can give off the same unpleasant odors as pee.

Ammonium is the source of the urine odor. You will smell a pee-like odor if something in your AC can release it into the air.

Small animals may leave their urine in your air conditioner, which I will discuss in the following section, but this is uncommon.

Why does my AC smell like pee? 3 common causes

causes of urine smell in ac

Running a dormant air conditioner can cause a foul odor. Where does the pee-like odor come from if not from real urine?


Mold can grow and thrive in the machine, such as air vents, air filters, or coils, if it is stored in a humid environment or the drainage hose is clogged.

Mycotoxins are produced by mold and can release chemicals that produce a foul odor. The most common type of mold, black mold, has a smell that is very similar to cat pee.

You might remember the smell from some basements. Doesn’t it also smell like pee? This is also due to the basement’s high humidity, which fosters mold growth.


Bacteria, in addition to mold, can appear in your air conditioner. Bacteria require food to survive, and our dead skin cells are an excellent source.

Our skin regenerates on a daily basis, and dead skin cells can be left on the sofa or desk, or they can linger in the air.

When the air conditioning system is turned on, it draws air in through a built-in fan. These dead skin cells can attach to the air filter and begin to be digested by the bacteria on the filter.

As you know, keratin is the main protein of our skin and hair. In the process of degradation of keratin, it will produce a pee smell.

Rodent animal

Even if the pee smell in your AC is not caused by humans, small animals such as mice and birds in your area could be the culprit.

Because it is warm, the air conditioner could be a comfortable place for these little creatures to live. Some people like to mark their territory by leaving urine and feces in it. The air duct is always their favorite location.

Occasionally, they will die in the AC. The decomposing carcasses will also release a pee-like smell. 

How do you get urine smell out of an air conditioner?

Now that we know why your air conditioner smells like pee, let’s look at how to fix it. The urine smell will be easily removed once we understand how to deal with mold, bacteria, and household pests.

Clean the air filter 

clean ac filter

With time, the air filter can accumulate mold spores, dust, dirt, and dead skin cells, making it the primary source of urine odor in your AC.

It is recommended that the ac filter be cleaned every 30 to 45 days. Fortunately, this task does not necessitate the assistance of a professional. After disassembling it, rinse it under running water with a brush to remove the sticky stain and debris.

To completely eliminate the bacteria and mold, use antibacterial soap or cleaner.

Always allow it to dry before replacing it.

Clean the coil 

Coils can also become filthy. Furthermore, due to frequent freezing and other factors, it can become rusted and moldy. That is, the coils may also invite a urine odor.. 

However, cleaning the AC coil could be more complicated. You can use compressed air or some mild detergent to do it. 

Unclog the drainage hose 

A clogged drainage hose can cause excess water in the AC and, as a result, mold growth. To unclog it, disassemble the hose from your air conditioner and clean out the debris and buildup in the hose.

If it is too hard to get it cleaned, you can consider replacing a new one.

Remove dead animal

If none of the above methods work, you can investigate your air conditioner and air ducts to see if there is any dead animal.

If you can easily reach the animal, put on a pair of gloves and place the dead body in a plastic bag. If the animal is difficult to reach, you should consult a professional.

How to prevent urine smell in your air conditioner?

After getting rid of the urine smell, the last thing you want to see is this strange smell come back after a while. Luckily, there are some ways to prevent it. 

Regular maintenance 

Cleaning the AC filter regularly and getting the whole air conditioning system serviced by an HVAC expert every 6 months can make sure your AC runs at high efficiency.

It also ensures that there is not enough food source for mold and bacteria, and the buildup will not clog the hose and vents.

Make use of repellents

Place some repellents or deterrents around the vent to drive the small animal away from the vent. That way, they will not relieve themselves in the air ducts.

Install thick screens

This is another effective way to prevent rats and pests get into your house and your AC system.

Improve the indoor air quality

Again, dead skin cells and other impurities could be the food source of mold and bacteria, which invite the urine smell.

If you can improve the indoor air quality, fewer impurities will get into the AC, and your AC will have much less chance of forming a pee smell.

Final thoughts

This post has illustrated the causes of a pee-like smell in an AC and how to deal with it. 

The urine smell is frequently caused by mold and bacteria in the system rather than by actual urine. As a result, the most important thing to do to keep it from happening again is to keep the AC clean.

Animals may accidentally leave urine in it, and you can keep them away by using repellents or installing thick screens.

About The Author

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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 dozens 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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