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How to stop smells from coming through vents

Updated on November 14, 2023
Written by
Conroy Baltimore
Conroy joined the HouseFresh editorial team in 2023. He is an experienced writer, who has honed his skills in home improvement writing in-depth guides for Angi. In his spare time, you can find him playing basketball or video games.

Unclean air ducts can lead to an overall decrease in air quality and comfort due to the foul smells that can leak through your vents.

Cleaning your vents, filters, and ducts periodically can ensure your HVAC system works efficiently without creating bad odors. You can do it yourself or with the help of a professional service.

Have you ever walked into your home and caught a whiff of a strange smell? You recently cleaned the house from top to bottom but didn’t catch any odd scents. Now that the aromatics have worn off, a stale smell is coming from somewhere. Where could it be? 

Unfortunately, the smell might be coming from your vents. It’s not a likely culprit that people may think about. However, they do get dirty from debris and other factors. If left unchecked for some time, smelly odors will appear. 

The smell coming from your air ducts could be from various sources, such as:

1. Mold and mildew
Air ducts are the ideal home for mold and mildew: dark, cool and damp. When you have an oversized unit in your home or leaks in your ventilation system, the water condenses, promoting mold and mildew growth. Other factors like flood waters and their aftermath can also lead to mold and mildew issues.

2. Clogged air filters
Air filters remove the impurities in the air to ensure maximum comfort. Over time, the particles can build up, reducing airflow, and the collected material may start decaying, leading to foul odors.

3. Dead animals
Unfortunately, there may be a time when a rodent—like a mouse or rat—finds their way into your ducts and dies there. When they start decaying, the smell can find its way through the vents and into your home.

In this article, I will take you through the steps you need to follow to stop smells from coming through vents.

How to remove unwanted smells from your vents

Before you do anything, you’ll need protective gear, such as a mask, goggles, and gloves. You’ll also need a screwdriver to help remove the panels, a vacuum cleaner and cleaning cloths or paper towels.

1. Vacuum and clean the vent cover and duct

Once you’re suited up, your first step is to unscrew the vent covers from the wall and vacuum the vent slats to remove cobwebs and other debris. You can do some additional care by cleaning the dust around the area and as far as your vacuum can go down the ducts.

After you’ve removed and vacuumed the vent cover, it’s time for a deep clean. Your best bet is to use warm water, soap, and a scrubbing item to remove debris. Usually, that should be enough to remove the smell from your ducts. But sometimes, you’ll need more oomph. 


To keep the air in your home fresh for longer, place a small amount of baking soda in a stable container and set it in the duct.

2. Change the air filters

The smells may be coming from decaying debris on clogged air filters that start smelling and seep through the vents. When did you last replace the air filter in your HVAC system? It might be time for a change if it’s been more than six months. 


5-step process for changing a furnace filter:

1. Turn the furnace off
2. Locate the service panel
3. Remove the existing filter
4. Replace with a new filter (we recommend using a HEPA filter because of its purifying prowess and durability)
5. Reattach the service panel and turn the furnace back on

Now that you’ve changed the filter, the bad smells should be non-existent in your home. Hopefully, this makes a difference. If there’s no noticeable change, you’ll have to look at another part of your unit.

3. Clean your evaporator coil

The evaporator coil is an integral part of your AC unit. It’s the main reason you can survive the heat on those brutal summer days! Since it’s working so hard to keep your home cool, the condensed water is also a hotbed for mold and mildew to grow. Lack of care can also lead to issues such as higher energy bills and ice buildup.

To avoid these issues, cleaning your evaporator coil is essential. Plus, it’s an easy enough task, so you can get it done quickly.  


5-step process for cleaning an evaporator coil:

1. Locate the access panel and remove it to expose the metal fins and condenser coils. Most central AC units have it on the back.

2. Use your vacuum attachment to suck up any loose debris. If it has a brush, use that to dust the excess of the fins.

3. Straighten the fins with a fin comb or flathead screwdriver, and remove the screws holding them in place.

4. Spray a mix of bleach and water to clean the coils (bleach ratio of 50 to 1). There’s also a collection tray underneath that holds excess water—wipe that down, too.

5. Reassemble the unit, run it, and see if that does the trick.

4. Unclog your condensate line

Excess condensation can form on the evaporator coils, drop into the collection pan and exit through the drain. However, the drain line can get clogged, leading to water backing up in the tray. As a result, it could lead to mold growth.

How would you know there’s a clog in the condensate line? Look for signs such as:

  • Mold growth
  • Musty smells
  • A pool of water around the inside of your AC

Clearing the clog takes a few minutes using a wet/dry vac. On the other hand, if the blockage is too stubborn and the wet/dry vac can’t get it done, it would be better to call a professional.


Look for signs such as:

.Mold growth
.Musty smells
.A pool of water around the inside of your AC

5. Dispose of dead animals

If you think a dead animal is decaying in your air ducts, call a professional pest control service to come and remove it. Remember, these are wild animals, and they carry harmful diseases. The sooner you get them off your property, the better. Let the professionals handle it!


You can use Angi’s ‘Near Me’ tool to find pest control companies near your area: https://www.angi.com/nearme/exterminators/ 

Final thoughts

Still not sure whether the smell is indeed coming through the vents and not other areas in your house?

  • Does the smell persist even after removing the trash and cleaning your home thoroughly? (especially the kitchen and bathroom)
  • Are there foul smells present when your HVAC system runs? 
  • Is the smell throughout the entire house as opposed to just one room?  
  • Is the odor the same in all rooms?  

If you answer ‘yes’ to any of the questions above, then it’s probably time to clean your air ducts. We wrote a complete guide to help you do it without the help of a professional.

No homeowner wants to deal with persistent foul smells. They can impact your air quality and overall comfort. Check your vents to look for signs of built-up debris and mold growth. You should also check other parts of your HVAC unit to see what else could be causing a smell throughout your home. Removing these restrictions can keep fresh air going through your ducts and everyone happy.


About the author

Conroy Baltimore

Conroy joined the HouseFresh editorial team in 2023. He is an experienced writer, who has honed his skills in home improvement writing in-depth guides for Angi. In his spare time, you can find him playing basketball or video games.