Air Conditioner Smells: How to Identify and Solve Bad A/C Odors | Rinaldi's
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Easy Ways to Remove Air Duct Odors from Your A/C Vents

Follow These Easy Tips to Improve the Air Quality in Your Home
Apr 27, 2021

Ductwork moves air from your home’s HVAC system to all the rooms in your living space. When you first turn on your A/C or furnace, you might notice a musty or foul odor permeating out. If that odor persists, you should address the problem immediately. Taking action to remove air duct odors can help your family breathe easier. But what can you do to remove odors from your air ducts?

What Kinds of Smells Can Come From an Air Duct?

The first step is to determine the cause of the bad smell. The cause of the smell will determine both what the odor actually smells like and also how best to remove the odor. There are several different possible smells that can come from your air ducts. First, ask yourself: What does this smell remind me of?

  • Musty or moldy odor (stale air, stinky feet, or dirty socks)
  • Sewage
  • Rancid (rotting garbage)
  • Burning
  • Rotten eggs
  • A freshly-struck match or sulfur

How to Get Rid of a Musty or Moldy Odor

A musty or stale smell that may be reminiscent of dirty socks or stinky feet is typically caused by mold or mildew. If your home smells musty or moldy, you may have mold growing in your air conditioner. But how can you get rid of that smell?

Check for Mold

Take a look at your condenser coils, as well as the drip pan. You may find mold growth in both locations. When water condensates on the coils, it provides a great place for mold to grow. The dust can also float off and down into the drip pan. If dust plugs the pan’s drains, water will remain in the pan, forming another ideal place for mold to grow.

Dirty AC

Clean your Evaporator Coils

You can clean your evaporator coils to remove excess dust. Also, you should clear the drain plug in the pan. This will keep water from moving and prevent mold growth. Another possible location for mold growth is your ductwork. Check inside vents and air returns to see if you can see mold, which can occur when your ductwork sustains damage from water.

Use Soap or Detergent

If you find mold in your ductwork, use soap or a detergent solution to clean your ducts. Then, use a solution of bleach and water to prevent mold growth in the future. It’s also important to repair any damage to your ductwork.

How to Get Rid of a Sewage Smell

If the smell of sewage is permeating your house from your air ducts, then the most likely culprit is just what it smells like: sewage. If there’s a crack in your pipes or if the sewer line is backed up, then that would cause a smell of sewage. If the problem occurred close to an air vent, the sewage smell could get sucked into your HVAC system and then spread throughout your house.

If you smell sewage coming from your air ducts, then check for a backup in your sewer line or for damage to the pipes in your plumbing system. Repairing the plumbing problem will get rid of the smell.

How to Get Rid of a Rancid Smell

When the smell coming from the ductwork is more rancid (like rotting garbage) than moldy, you may have a dead animal somewhere in your system. It’s quite common for mice and other small animals to chew through ductwork and use them as avenues. Get an exterminator to deal with your pest problem, as well as the dead critters in your ducts.

How to Get Rid of a Burning Smell

If you can smell burning coming from your air ducts, first check to make sure nothing is actually on fire. Once you’ve eliminated a real fire as a possible cause of the smell, then check your heater. If the burning smell is strongest close to the heater, then the heater’s fan may have a problem. If the heater is having mechanical issues, then those can cause friction with the fan as it moves, causing the burning smell. Fix the heater problem and the burning smell should go away.

How to Get Rid of a Rotten Eggs Smell

Natural gas is actually odorless. The smell of rotten eggs actually comes from an additive mercaptan. Mercaptan is added to natural gas coming into homes on purpose so that it’s possible to detect by smell when there’s a gas leak. If you smell rotten eggs coming from your air ducts, it means there’s most likely a gas leak in your home. Open the windows, leave the house, and call your gas company in to find the leak and repair it.

How to Get Rid of a Sulfur Smell

If you smell sulfur, or the smell of a freshly-struck match, coming from your air ducts, there are two possible causes. The first is a failure of the mechanics or electronics inside the heater. This could be something like a short in the circuit board within the heater. Repairing the heater should remove the smell.

The second possibility is Chinese Drywall. The term Chinese Drywall refers specifically to a batch of defective drywall originating in China (not all drywall from China) that was used in the construction of some American homes between the years 2001 and 2009. It’s estimated that about 100,000 homes across 20 different states are affected by Chinese Drywall. Chinese Drywall can cause health problems as well as a bad smell, so if your home is affected, it’s important to replace the drywall.