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Smell from air ducts, why and what to do now?

Smell from air ducts? Smell from your HVAC system? Let’s cover the main reasons why and what to do about it, how to fix fast.

If a strange scent emanates from your ducts whenever your heater or air conditioner is operating or whenever you just turn it on and sense weird smells, it indicates that there is a problem with your HVAC system. 

Such odors could be coming from fragments stuck in your ductwork. Not only may dirty air ducts bring in odors, but they can also spread these displeasing odors all over your house.

It’s crucial to understand the origins of the most prevalent air duct odors because different smells signify different kinds of problems.

Why Do I Have Smell from Air Ducts?

There are many different factors that can generate odors in air ducts. Smells from mold, animals, or other waste might become caught in your ducting. Outside odors in your home could appear to originate from your ducts, but they’re actually brought in by other sources and spread through the vents.

Mold and mildew, building materials, duct leaks, plumbing leaks and troubles, animals in your home or ducts, or mechanical problems, such as a defective blower motor that is overheating, can all contribute to unpleasant odors in your ductwork. 

The good thing is that a lot of these odors can be recognized and connected to their causes, which will make locating and getting rid of the odor much simpler.

Moldy or Musty Smell

The most prevalent problem with HVAC systems is certainly an odor similar to mildew or mold. There is a lot of moisture within the air conditioner when it is operating. If the moisture isn’t adequately drained, it can go into the ducts and result in mold growth. The issue can be resolved by locating the mold buildup and having it cleaned up.

Stale Air, Stinky Feet, and Dirty Socks

You probably smell these types of smells when you have mold or mildew issues in your heater and ductwork, as well as in areas where your ductwork disperses these odors. If you can identify any places in the house where the odor is more obvious, you may have found the source. 

You should consult air duct cleaning services if there is a lot of mold or mildew in a place, since huge concentrations of mold or mildew can trigger serious respiratory problems for you and your family members.

Burning Gas Odor

You usually don’t have to worry about burning gas odors coming from your air ducts when you start your heater. This type of smell comes from the air duct when the dust trapped inside the air duct burns off the heat exchange. Ideally, this odor should dissipate within a few minutes.

If you sense a burning gas odor and realize that it is not originating from air vent registers, then this is an indication that either the HVAC system or a pipe junction has a leak. If so, get in touch with an HVAC professional from air duct cleaning services so they can find the leak and repair it promptly.


There is just one typical reason why your vents might smell like raw sewage, sewage obviously. This could occur if sewer lines are clogged or a crack occurs in plumbing or sewer vent pipes. Your home’s ducts may be able to disperse the odor if it is located close enough to them.

Rotten Egg Gas Odor

If you notice a scent that reminds you of rotten eggs, natural gas has likely escaped from someplace within or close to your home. This is a potentially dangerous and highly serious scenario. Ventilate your home by opening the windows, then leave right away.

In such a situation, contact your legal gas providers to close the gas opening and repair the fault right away. If the HVAC system is the source of the gas leak, a specialist will be needed to fix or replace the broken component.

What Causes the Musty Odor in My Air Conditioner?

Air-conditioned homes are the perfect place to escape the summer heat. However, you need to take quick action if you notice a weird, musty odor. What does it signify when your air conditioner starts to smell musty? In essence, a musty odor is an indication of bacterial growth accumulation on the drain, drip pan, evaporator coil, or drain line of your air conditioner. 

All kinds of mold and mildew can grow on your evaporator coil because it is a dark, moist environment, which results in that musty odor.

The following are the pointers you need to remember to identify the cause of the musty AC odor.

  • Check if your vents or ducts have too much moisture.
  • Look at your AC drain pan to see if it is full.
  • Determine whether your condensate line is blocked.
  • Evaluate whether your HVAC system size is appropriate for your home.
  • Look for iced evaporator coils.

Why Are Unusual Smells a Problem?

All scents emanating from your ductwork, whether they smell like mildew, filthy socks, or rotten eggs, point to a problem with your AC system. Just as we discussed earlier, the smell of rotten eggs is associated with gas leaks, the burning gas smell is linked with dust burnt in the air duct, and the musty odor is a sign of mold growth inside your AC ducts. 

Whatever the smell is, you should also inspect the source of the smell because unpleasant odors coming from an electronic appliance are never a good sign. It is critically important to root out the issue quickly. Furthermore, the problem can aggravate and damage your HVAC system, resulting in expensive damage repairs or may require you to replace the entire AC unit.

Typically, a musty smell indicates that your air conditioning system may contain impurities. Your system is a perfect environment for bacterial growth since it is dark and damp. This indicates that your air conditioner is dispersing harmful mold spores into each area of your house. These spores can seriously harm your health, particularly if someone in your household has allergies.

Never disregard unusual odors coming from your HVAC system. The easiest method to solve your odor problems is to have a qualified air conditioning expert from air duct cleaning services inspect your system.

Managing HVAC Smell

Air Duct Smell

Many HVAC units generate more odors because of the tight construction of homes today, which lack proper ventilation. The system runs out of air for combustion as a result. For many homeowners, this can be the main reason for unpleasant HVAC odors. 

Having unpleasant odors in your home means breathing in low-quality air. The odors coming from the air duct become a serious concern as unhealthy air affects the health of the residues.

The stench of dirty socks is another sign that there is an issue with the indoor air quality. Although the air conditioner may be the source of this odor, the air conditioner itself is not the issue. In most cases, organic material is likely to grow if it has not been heated sufficiently.

The heat exchanger in the majority of units destroys biological material. However, heat pumps prevent those temperatures from being reached. Poor air quality results from the release of mold and spores into the air through the heat ducts. An HVAC specialist from air duct cleaning services can identify the issue and make recommendations for fixes.

If you have been following our blogs, then you must be aware that we’ve always emphasized the significance of vent and duct cleaning. Dirty air ducts and vents harm the HVAC system and directly affect the health of those around them.

We all look for a chilled, air-conditioned environment to escape the blazing heat. However, it is equally important to take care of your HVAC system so that you can continue enjoying a pleasing environment without any interruptions. All you have to do is to look for signs of mold growth or any other particles trapped inside the air duct. If you have sensed any weird odors, immediately start looking for the sources of the odors so that the problem can be quickly fixed.

Many people overlook the importance of HVAC system maintenance and end up spending ample money on repairs. Regular air duct cleaning from air duct cleaning services can save you from all this hassle. If you don’t know the basics of your HVAC system, it’s recommended that you contact professional HVAC cleaning services.

What’s Making Your Home Smell Like Must?

Check for mold or mildew growth in the following places if you have a musty stench that won’t go away:

Excess Moisture on Evaporator Coils

If the evaporator coils have too much moisture, mold spores grow on them, and the air that flows over them circulates them through the ductwork, causing a musty odor in your home.

Inappropriate Fan Speed

If your unit’s fan speed is set wrong, it may cause moisture to build up in your ducts. Mold or mildew will develop in your ductwork in the presence of too much moisture, filling your rooms with a musty odor.

Cracks in Basements and Attics

Water from leaking roofs or moist walls will seep into ductwork through loose joints or cracks in attics and basements. This may eventually lead to the development of mold in return air ducts. Mold may also develop if the insulation protecting the ducts in unconditioned locations collects moisture. Additionally, ductwork cracks may allow the musty odors to penetrate.

Clogged Filters

Moisture build-up appears in your return ducts due to clogged filters, thus leading to the growth of mold, mildew, and a musty odor.

Clogged Condensate Drain

Air handlers discharge extra water which is removed by the condensate drain. When the drain is clogged, the extra moisture seeps into the ducts where it breeds mold, mildew, and an unpleasant musty odor.

Some Important Things to Remember:

Never attempt to perform AC repairs on your own. Always get a pro to complete the task for you. By “pro,” we mean an air duct cleaning service professional with the necessary expertise to deal with HVAC issues. It is advised that you call a professional since a lot of things happen when you touch an electrical appliance to repair it. In the case of an HVAC system, electric shock can occur if electrical components are in contact with water. At such a time, it is advised to refrain from trying anything new at that time.

If you believe you are competent enough to fix the HVAC system issues and perform HVAC duct cleaning, make sure you have read the operation and maintenance manuals for your air conditioner carefully. Once done with the theory part, brace yourself for the action and start by assembling the required tools. Last but not least, shut off the power source to your air conditioner and prepare the necessary personal protective equipment (PPE).

Additionally, avoid attempting to cover up the unpleasant odor with an air purifier or refresher. It will only worsen the situation. Delaying necessary repairs will only make your air conditioner worse and may force you to buy an entirely new system.

Air Duct Cleaning Services, HVAC cleaning

One option for getting rid of the musty smell in your ducting is to clean your air conditioner. Let’s see what steps you can take in this regard.

Maintain the Evaporator Coil

The evaporator coil is the major component of your air conditioner that is responsible for cooling your house. However, when it becomes dirty, mold can easily develop there. To clear it out, you should take the following actions:

  • To begin with, get a 10% bleach water solution. Don’t think right away that bleach would harm your coil system. A bleach solution is effective in eradicating mold without endangering the coil system. However, you must always remember that bleach should always be diluted with water because it can corrode metal if it is not. If you are suspicious about using a bleach solution, then you can also use standard coil cleaner to clean your evaporator coil.
  • The back of most central air conditioning units has an access panel. Remove this to see the condenser coils’ metal front fins. Make sure the fins and coils are free of dust and debris by using your vacuum with an attached brush.
  • Also, you can use a fin comb or flathead screwdriver to straighten any bent fins. Most appliance stores sell these tools. Four to eight hex screws will be holding the fins in place, so remove them.
  • Once the coils are sprayed with bleach, wipe them down with a soft cloth. Wipe down the collection pan as well. Assemble the parts and operate the AC unit to observe if the musty odor has been eliminated.

Fix Plumbing Issue

If your air ducts smell like sewage, look for a backup in your sewer line or damaged pipes in your plumbing system. To eliminate the smell, you will have to fix the plumbing issue.

Look for Mold

Your condenser coils and drip pan need to be examined. In both places, mold development is possible. Mold can easily grow on coils where water condenses because of the ideal conditions it creates. Additionally, the dust may drift off and fall into the drip pan. Water will linger in the pan if dust clogs the drains, providing yet another perfect environment for mold to flourish.

If you spot mold growth, call professional air duct cleaning services right away. The professionals will inspect your HVAC system and thoroughly check your home to find the sources of mold growth. The detailed air duct cleaning by professional air duct cleaning services provides you with dirt-free indoor air in which you can safely breathe.

The Duct and Vent Cover Should Be Vacuumed and Cleaned

When trying to eliminate odors from your vents, vacuum the duct and vent cover. To remove all the dirty particles and grime lodged there, make sure the vent is removed from the wall and the slats between them are vacuumed. When you remove the cover, you will be able to see everything on the vent’s back and front faces. 

Dust and debris may be trapped inside the vents, so vacuuming up any dust you see in the ducts is important to keep air flowing smoothly.

Cleaning the vent cover is easy. Using warm water and soap, you can easily clean the vent cover, taking off the more tenacious material by using a brush or other scrubbing tool. At the same time, you can clean the duct. If you put baking soda in the duct before replacing the cover, it can help reduce odors. The baking soda can be put in a bowl or a non-spilling box.

Replace or Clean your Filter

Your air filter may occasionally become so clogged with dirt that airflow is impeded. As a result, your ductwork may become clogged with dust and moisture, which can act as a mold-growing environment. Therefore, cleaning your air filter is generally a smart idea if it appears extremely dusty. But if thorough vacuuming and cleaning are insufficient, you might need to completely replace the filter.

Check the Heater’s Fan

The first thing you should do if you smell burning from your air ducts is to make sure there is not a fire there. Inspect your heater once you’ve ruled out a genuine fire as the source of the odor. The heater’s fan might not be working properly if the burning smell is worse in the area closest to the heater. The burning odor may be brought on by friction between the heater’s moving fan and any mechanical problems.

To fix the heater issue, call an HVAC-certified technician.

Final Thoughts

Strange odors coming from your HVAC ducts are never a good sign. Fortunately, the foul smells can be identified, which also indicates the source. Be vigilant since natural gas leakages, water leakages, mold and mildew growth due to moisture and condensation can harm your HVAC system and eventually deteriorate indoor air quality. When you witness such signs, contact professional air duct cleaning services that can give you the best solutions.

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