Erase Air Conditioner Smells with Proven Solutions

When you switch on your air conditioner, you expect to feel it – not smell it! We often hear from homeowners who are experiencing some stinky side effects when they use their cooling systems, so we’ve put together some information that will help you get to the bottom of air conditioner smells, learn their causes, and find solutions which will rid your home of these foul odors.

Smelly Air conditioner

What Causes Air Conditioner Smells?

In most cases, air conditioner smells are caused by mold and mildew growing somewhere within the system. As air circulates throughout your home, many airborne contaminants have the opportunity to settle within the system; even when your air conditioner is idle over the winter, dust and dirt can collect. Contaminants within your system paired with the cool, damp conditions within can cause mildew and mold can form within your equipment, and the smell can carry into your home as the system circulates cool air throughout your home.

Smells coming from your cooling system could also be stemming from a dirty air filter. Your system’s filter works to pull odor-causing contaminants out of the air supply as it circulates. If you have not been changing your air filter on a regular basis, these captured contaminants could be recirculating back into your home when the air conditioner is in use.

Often, homeowners may think a smell is originating from the air conditioner when it is actually being picked up somewhere else and circulated through the HVAC system. Chemical cleaners, exhaust fumes, perfumes, candles – these odors could be created somewhere else inside or outside the home and be transported throughout the house through the duct system.

Odor-Causing Zones in Your AC System

Evaporator Coils

Through the course of normal use, dirt, dust, and other debris are deposited on the evaporator coils of your cooling system. These particles paired with the damp, cool environment of the evaporator coil create the ideal breeding ground for mold and mildew.

The drain pan and condensate drain line which carry moisture out of your evaporator coils can become clogged. When moisture is unable to flow out of the system, mold and mildew can also form in these components.

Air Filter

As mentioned above, odor-causing contaminants are often concentrated in your system’s air filter, as the purpose of the air filter is to pull them from your air supply so they do not reach your living areas. Neglecting to change your air filter regularly is essentially leaving more smelly particles in your system, and providing the opportunity for them to be carried back into your home as air circulates.


Debris can accumulate in the ductwork of your home as air circulates. If moisture isn’t being controlled, the environment inside your ducts can become damp, creating opportunities for mold and mildew to grow.

Gaps, holes, and breaks in your ductwork can allow outside odors to enter the duct system and be circulated inside your home. Mold and mildew stemming from a roof leak or wet crawl space could be entering your duct system through these disconnections and be the source of your mold smells, especially if your evaporator coils and filter are clean. Other odors such as exhaust fumes and chemicals could be entering broken ductwork if sections run through your garage.

How to Fight Air Conditioner Odors

Change Your Habits

Work to rid your home of odors by making simple changes in your daily habits:

  • Always use exhaust fans when cooking and showering.
  • Make the switch to natural cleaners which do not emit toxic fumes.
  • Vacuum floors, clean surfaces, and wash linens frequently to remove contaminants from the home.

Change Your Air Filter & Use a High-Efficiency Filter

If you haven’t been changing your air filter on a regular basis, it’s time to step up. Regular filter changes will remove contaminants from your system so they cannot be recirculated back into the home – less contamination equals less smell. The frequency that you should change your air filter will depend on the type of filter, as well as other factors, such as if there are pets in the home.

Make the switch from standard disposable filter to a high-efficiency air filter in your home. Filters with higher MERV ratings have the ability to remove smaller contaminants which are often responsible for odor in the home, such as bacteria and mold spores.

For additional air freshening benefits, try adding your favorite essential oil to your air filter.

System Cleaning

Your air conditioning system’s evaporator coils should be cleaned annually by an HVAC professional. Having your system’s evaporator coil cleaned not only works to reduce smell, but the procedure will also improve the efficiency of your air conditioner. The mold, mildew, dirt, and other particles caked on your coil will reduce airflow through the system, lowering its efficiency. Improved efficiency typically translates to longer service life, which can help you avoid costly early system replacement.

Duct cleaning is another professional service that can help you remove odors. During duct cleaning, contaminant buildup is removed from the system, never to recirculate again.

You should check your drip pan and condensate drain line monthly during cooling season to make sure they are working properly and that excess moisture isn’t causing mold or mildew to form here.

Install an Air Purifier

A whole home air purifier (also called an air cleaner) works to pull pollution out of your home, creating a cleaner indoor environment. They can remove up to 99 percent of bacteria that exists in your home’s air, as well as remove odors emanating from cooking, cleaning, and daily life.

Ultraviolet lights are a type of air purification system which can be installed within your home’s duct system and coils to eliminate existing and control the growth of mold and mildew. As air circulates, UV-C energy produced by the bulbs destroy mold spores, bacteria, viruses, and other harmful contaminants while controlling regrowth in the system.