How to Remove Musty Air Duct Odors from Vents

Updated on April 4, 2016

While central heating and air systems are a godsend in the hot summer months and on cold winter nights, they can become a nuisance when they spread a musty odor throughout the house. After a few hours, you may find yourself asking, "can I clean my air ducts myself?" The answer is a qualified yes.


Before you can begin to tackle the problem of the smell from your ducts you have to determine what might be causing it.

  • Mold. One of the most common causes of a musty smell in ductwork is the presence of mold in an air conditioner. The mold will grow on both the condenser coils and in the collection pan.
  • The ductwork. Another common issue could be with any of the ductwork that runs through a crawl space beneath the house. If the crawl space becomes flooded, this is a perfect environment for mold growth.
  • Dead animals. If the smell isn’t musty and falls into the more rancid category, you may have a dead animal on your hands. Often, a mouse or other small critter can chew a hole and crawl into the ductwork. If it dies in there, you will inevitably smell the rotting remains.

Cleaning Air Conditioning Units

Cleaning your air conditioning unit is one possible way to eliminate the musty smell from your ductwork.

  1. To clean the condenser coils and collection pan, you’ll need a solution of 10% bleach water. This is enough to kill off the mold without doing any damage to the coil system.
  2. Most central air units have an access panel on the back. Take this off to expose the metal fins in front of the condenser coils.
  3. Using your vacuum with the attachment brush, suck up any loose dust or debris from the fins and coils. At this point, you can also straighten out any bent fins with a flat head screwdriver or a fin comb, which can be purchased at most appliance stores. Remove the fins — they will be held on with four to eight hex screws. Now spray the bleach solution on the coils and wipe them down. Pull out the collection pan and wipe it down as well.

Reassemble the unit and run it to see if that has taken care of the musty smell.

Vent Filters

If the smell wasn’t coming from the air conditioning unit, then it may be coming from any part of the duct system. It may be impossible to find the cause without a snaking camera system.

The next best thing is to eliminate the smell is with duct filter pads. These hypoallergenic filter pads are available at most home improvement stores and are made to fit both vertical and horizontal ducts of all sizes.

  1. Simply unscrew your duct vent covers and place the filter pad into the grate.
  2. Screw the cover back on and let the filter catch the offending particles.

Baking Soda

For more immediate relief, the old stand-by trick of putting a little baking soda in a dish and placing it in the smelly area may work. You’ll have to put the baking soda directly in the duct. This will only work if the baking soda comes in contact with the offensive air particles. So, finding a way to expose more surface area to the air will improve results. Arm and Hammer currently makes a “fridge pack” that has a peel-off side. This will allow you to stand the box up and have a large surface area for the forced air to pass through.

Professional Cleaning Services

If none of these options have worked or if the smell seems to be coming from a dead animal, you will probably have to contact a professional duct cleaning service.

There are plenty of services to choose from. As a general rule, those that offer full household services for under $100 will usually not cover all of the duct work in your home. Do a bit of research to find a reputable company in your area. Expect to pay at least $150 for a professional cleaning.

Can I Clean It Myself?

How to get rid of the smell in your ductwork depends on whether it's a musty smell or a rancid one.

  • In the case of a rancid smell, it is almost always better to have a professional take care of the problem.
  • If it is a musty smell you may be able to handle it yourself. In fact, there are plenty of home improvements you can do on your own, but you have to start by finding them.

Questions & Answers

    © 2012 Everyday Green


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      • profile image

        Michael 6 weeks ago

        I haven't clean my duct at all, my kids start having allergies, my friend referred me to "Marius Duct Cleaner" they cleaned my system that was great.

      • profile image

        ms B 3 months ago

        The apartment in my building had major water pipe burst foul smell coming thru vent all through apartment smells like musty mole

      • profile image

        diana 19 months ago

        can you have a musty odor in the air ducts without having mold, and will heat kill the mold if there is some? also, the filters that are mentioned will they catch the mold spores if there is mold in the air ducts? I live in apt building we have central air and heating and each apt has a unit in it that runs off the main unit on the roof. no visible mold on the cover or on the duct work that can be seen... reaching as far in as possible there is no dampness felt nor is there any mold in contact. thank you

      • LisaRoppolo profile image

        Lisa Roppolo 3 years ago from Joliet, IL

        My vents I suspect haven't been cleaned in years (previous owner neglect). I'm having a musty smell when the heat kicks on, so I suspect it is coming from the vents and furnace unit. I am having it done professionally this time but these are great maintenance tips going forward!