Reasons Why Your AC Smells Musty & How To Eliminate the Odor

Reasons Why Your AC Smells Musty & How To Eliminate the Odor

There’s nothing better than having an air conditioning system during the hot and humid summer season. You can simply turn on your AC and have the comfort you need. But what if your AC smells like rotten wood? You don’t want to turn off the AC and have to go back to suffering inside but at the same time that smell is unsettling and overwhelming.

The question is why your AC smells musty — is it normal or is there something unusual happening inside the AC? If you experience an odor when you turn on the AC, it could be a sign of mold growing inside the unit or the air ducts.

First of all, you need to figure out the source of the smell. A variety of factors can lead an AC unit to release an unpleasant odor. A musty smell is a potential health hazard, so you can’t ignore it. In this post, we’ll discuss common reasons why your AC smells musty and what you can do to eliminate the odor.

Why Does My Air Conditioner Smell Musty?

A musty smell, whether it is coming from your AC or basement, is an indication of bacterial growth. Mold and mildew can grow inside an air conditioning system for many reasons. To avoid mold-related issues, you have to maintain your HVAC systems. Here are some reasons why your AC can smell musty.

1. Excess of Moisture in Vents or Air Ducts

When moisture builds up inside vents or air ducts, it creates a friendly environment for bacteria to grow. Moisture often accumulates inside your unit due to a drainage leak or high humidity level. Don’t let these issues go overlooked. If your AC is producing a bad odor, chances are mold or mildew has spread within the ductwork.

To eliminate the odor and more importantly keep your family from potential health issues, you need to act immediately. If you don’t know how to examine an AC, get professional assistance. Call an HVAC professional and have them take a look inside the unit. A simple solution is to clean the ducts and vents to get rid of the smell once and for all.

2. Frozen Evaporator Coils

A traditional AC unit takes the indoor air, removes the moisture from it, and cools it down. It is crucial to keep the air filters clean in order to accommodate free-flowing air. When you keep using dirty filters for too long, water drops from humid indoor air start collecting on the evaporator coil.

Eventually, those water drops freeze as your AC continues to cool the air. To avoid this problem, you must clean or replace air filters at least once a month depending on the dust level in the air.

3. Clogged Condensate Pipe

Another source of musty smells is clogged drain pipes where a variety of bacteria can grow. The condensate pipe is a component of your AC which is usually located outside of your home. The prime function of a condensate pipe is to drain water from the unit. An excessive amount of moisture inside the pipe creates an environment for mold, mildew, and other bacteria to grow.

If a clogged condensate pipe is the reason why your AC smells musty, then you have to clean the line. Turn off your AC and remove the condenser line. Then pour a cup of distilled white vinegar down the pipe to clean it. Wait for half an hour before rising the pipe with water. If you’re unable to detach or attach the condensate pipe, seek professional help.

4. A Full Drain Pan

If your air conditioner’s drain pan is full of water, it’s a sign of either a clogged drainpipe or water standing in the drain pan. The humidity is left behind in the form of condensation on the coil. The air blowing over these coils can leave traces of dust and dirt.

When dirt drips off in the water, it leads to a clog and stagnant water in the pan. This not only affects the performance of your AC but also creates odor problems as fungus start growing in the drip pan. The musty smell will not go away unless you clear and clean the drain pipe. The best solution is to call a professional and get the problem fixed as soon as possible.

How Does Mold Get in My Air Conditioner?

Mold spores keep traveling through the air until they find a favorable spot to land and breed. It can grow anywhere there is darkness, warmth, nutrients and moisture. Inside your AC or drain pipes, the mold gets everything it needs to multiply and produce musty smells.

No matter how mold got in your air conditioner, it’s important to get rid of it as soon as possible. Mold growth in your home is a potential health hazard. On top of this, severe mold can irreparably damage your AC and infect other parts of your house such as windows, curtains, and walls.

How To Eliminate the Musty Odor

To permanently eliminate the musty odor coming from your AC vents, you have to remove the mold and keep your unit clean. Here are some recommended methods you can apply to get rid of the smell and keep your unit working efficiently.

1. Flush the Drain Line

We’ve already talked about how drain line blockage can cause water stagnation and mold growth. This small pipe plays a key role in how your unit performs and how it smells. If you notice slow water drainage or your AC is leaking, it is a sign of a blocked drain line.

You can flush it yourself if you have a wet/dry vacuum, distilled vinegar, a cloth, and some technical knowledge of how to open an AC unit and flush the pipe. Above we mentioned how to clean the pipe with distilled vinegar. A wet/dry vacuum will help you suck out the blockage in a couple of minutes.

2. Clean the Drain Pan

If the drainpipe of your AC is blocked, you’re likely to find the drain pan filled with water. To clean the pan, you can wash it with some warm and soapy water. To get rid of the mold, you can rinse the pan with vinegar or bleach. Dry the pan before installing it back in place.

3. Replace or Wash Air Filters

If mold has accumulated on air filters, the best thing you can do is replace them. If your AC has reusable filters, you can thoroughly wash them with warm and soapy water. To kill the bacteria, rinse them with diluted bleach.

4. Eliminate Room Odor With a Natural Scent

After getting rid of the mold from your AC unit and drain line, be sure to use a natural air purifier to neutralize mold and mildew. Our Small Room Odor Eliminator Treatment is the best product you can use to improve the air quality of your house. To get rid of mold and mildew stain from different surfaces, use our MoldGold Cleaning Kit.

Closing Thoughts

A musty and lingering smell is a clear sign of mold growth. If you experience moldy AC smell or musty smell in your basement, it’s time to implement a mold removal method and restore the freshness of air by applying our all-natural, anti-microbial odor eliminator. Visit our shop to see the complete range of our air purifying products.


How To Clean An Air Conditioner | Forbes Advisor

How to Clean Your Air Conditioner's Condensate Drain Line | Home Matters blog | AHS

HVAC Maintenance | Forbes

Azuna's Best Sellers


Azuna Gets Harsh Chemicals Out Of Your House (and Your Life)

Here are a few of the many harsh chemical-laden products that Azuna replaces. Naturally.

Air Freshener Spray



Car Air Freshener

Dryer Sheets

Fabric Softener

You may not know this but some of the biggest sources of indoor air pollution are the very products that you use to freshen your home, your clothes and your cars. When used, these products release phtalates and other heavy, unnatural chemicals into your air. That's why, according to the EPA, indoor air (where the average American spends 90% of their time) is 2-5 times more polluted than outdoor air.