Why Does My Air Conditioner Smell?

6 mins read
Why Does My Air Conditioner Smell?

When did you last clean the air filter in your air conditioner? You might notice an unpleasant smell from your air conditioner vents if it’s been more than six months. Additionally, you may also see many smells that don’t seem to make much sense.

Many air conditioners smell because of mold or mildew growing in the vents or within your AC system. Every time you turn on your unit, you will send moisture into your system – a potential mold growth source.

Please keep reading to learn more about why your AC smells so bad and what to do.

Why Does My Air Conditioner Smell?

Your air conditioner is an essential device that provides excellent, dry, comfortable air during the hot summer. Unfortunately, it can also produce some unpleasant odors.

Below are some of the most common reasons why your air conditioner smells awful:

Mold. Mold is one of the ultimate common causes of foul AC odors. Your air conditioning system is made to withstand high humidity levels, but if your system’s moisture levels get too high, mold can start growing on the coils, in your ductwork, or in your drain pan.

Dirty AC Filters. Your filters can smell musty when clogged with dust, dander, and debris. Changing or cleaning your filters usually will prevent this from happening.

Dead Animals. If you smell a foul odor from your AC vents that smells like something has died, there’s a good chance that an animal got trapped in your ductwork while it was open and died inside. 

Is Strange Smells An Issue?

Are Strange Air Conditioner Smells An Issue

Strange smells coming from your air condition unit can be an issue. If a peculiar smell comes through your air conditioning vents, it could be toxic and never a good sign.

It’s easy to ignore strange smells in an air conditioner because it’s not always easy to pinpoint the source of the odor right away. However, if these odors are detected early, they can usually be treated easily. 

However, waiting too long may damage your system or cause severe health hazards.

Types of Air Conditioner Smells, Possible Causes, and What You Can Do

Air conditioners don’t necessarily smell like anything, so it can be unsettling when your air conditioner starts to smell. It is especially true when the smells coming from your ac are unpleasant. So what’s causing these smells? And how do you get rid of and eliminate them?

To help you, we’ve compiled this list of types of air conditioner smells, possible causes, and what you can do.

Air Conditioner Smells Like a Car’s Exhaust Fumes

If you turn on your air conditioner and smell like a car’s exhaust fumes through the vents, don’t panic. It’s unpleasant, but it doesn’t mean your AC is broken. Instead, it’s probably due to one of these three factors:

  • It could be because of a damaged heat exchanger. The heat exchanger needs to be carefully maintained to function properly. 
  • If the heat exchanger is damaged or broken, dangerous gases can escape your home.
  • You likely have a refrigerant leak. A refrigerant leak is unpleasant, but it can also be potentially dangerous.

Solution. We recommend that you call a professional to inspect the heat exchanger as soon as possible if you recognize this smell coming from your AC unit. In the meantime, open the windows and ensure your home is well-ventilated. It will keep the smell out and prevent any dangerous effects from chemical leakage.

Air Conditioner Smells Like Something Is on Fire

Air Conditioner Smells Like Something Is on Fire

This one is scary, we know. But fortunately, it’s not always as serious as it sounds. There are two common reasons why your AC could smell like fire:

  • A broken electrical component within the unit could be causing the smell and could pose a danger to you and your home.
  • If you have a gas leak, the ducts leak, and the smell comes through your vents.

Solution. Start by changing the air filter. Look in your owner’s manual for instructions on finding and changing the filter, or ask a professional to help you. You should also monitor if the condenser coils need to be cleaned or if the ductwork needs work before the next cooling season starts.

If Your Air Conditioner Smells Like Rotten Eggs

If you’ve noticed an odor like rotten eggs coming from your AC vents when you first turn it on for the season, it’s likely due to bacteria in your ducts over time. 

Rotten egg/sulfur smells can come from two sources:

  • A crack in your air conditioner’s heat exchanger could leak carbon monoxide into your home’s air.
  • A dirty or blocked condensate drain allows water to build up, overflow the drain pan, or drip onto the floor.

Solution. (1) Pour bleach down the condensate drain to kill any bacteria. (2) Clean out the condensate pump (if you have one). (3) Remove any blockage in the drain line, if possible.

If Your Air Conditioner Smells Like Skunk

If Your Air Conditioner Smells Like Skunk

A skunky odor from your air conditioner is typically caused by mold or mildew growth in the condensate drain line or drip pan. It is one of the most common air conditioner smells and is usually easily fixed.

  • It is probably a sign that the condensate drain line is blocked. 
  • It can be due to mold or algae buildup within the drain line, which can be cleaned with water and bleach.

Solution. The best way to eradicate the smell is to clean the condensation drip pan and drain line with a mild bleach solution (1/4 cup chlorine bleach per gallon of water). You can use a turkey baster to flush out the drain line or pour the key into the drip pan directly if it’s accessible.

Getting a Moldy or Musty AC Smell

If you smell mold or mildew when you turn on your AC, mold may grow somewhere in your unit. 

  • A common location is where water has accumulated in the drip pan or drain line. 
  • Mold needs moisture and warmth to grow—two things abundant in an air conditioner—so it’s crucial to take action quickly if you smell mildew or mold.

Solution. First, you should shut off your unit and contact an HVAC professional to help diagnose the problem. You can also buy a biocide tablet (usually iodine) and pour it into the drip pan through the drain line to kill any existing mold spores. However, it will not remove the spores or solve any underlying issues that caused them to grow in the first place.

Air Conditioner Smells Like Cigarette Smoke

Air Conditioner Smells Like Cigarette Smoke

If your AC smells like cigarette smoke, it could be caused by several things:

  • the smell of cigarette smoke can remain in your home for a long time after someone smokes inside
  • your family or pets may have tracked smoke into your home on their clothing or fur
  • you may have accidentally sucked cigarette ash into the vent

Solution. (1) Get some air freshener and spray it around your home. (2) Use a deodorizer that you plug in to neutralize the odors. (3) Burn incense to help mask the smell.

If neither of these steps works, try changing the filter in the unit and replacing any disposable filters you may have, or you may need to clean them with a vacuum or cloth.

Why Does My Air Conditioner Smell Like Vinegar?

Your air conditioner is supposed to keep you cool and comfortable, but that’s tough to do when it smells like vinegar.

  • The common cause of an AC unit smelling like vinegar is bacterial buildup in the drip pan or drain line. 
  • The drip pan is located under your evaporator coils, and it’s responsible for catching condensation. 
  • Sometimes this condensation pools, which allows mold and bacteria to grow.

Solution. (1) This problem can be solved quickly by simply cleaning the coils. However, if that doesn’t work, you must replace or repair the evaporator coil. (2) Another solution is to grab some bleach from under the sink, pour it into the drain pan, and let it sit for at least an hour—overnight is even better. (3) The bleach will kill off all the bacteria and mold in the drainage system, eliminating that disgusting smell.

Is Smelly AC Bad For You?

The answer is yes; most of them are. 

According to the EPA, three prominent smells come from your AC unit: wet dog (bacterial growth), rotten eggs (sulfur gas), and car exhaust (carbon monoxide).

Your AC circulates all of the air in your home. If your AC smells like mildew, mold grows in your unit, and you breathe in mold spores. It can cause several health problems, such as infections and skin irritations.

Mold can also affect your immune system and the lungs, causing allergic reactions and inflammation. The most susceptible are asthma, allergies, or weakened immune systems (infants, pregnant women, people with HIV/AIDS, or cancer).

How Do I Get the Musty Smell Out Of My AC Vents?

How do I get the musty smell out of my AC vents?

If you notice a musty smell from your AC vents that persists even after changing the filter, mold is likely growing inside your air ducts.

Fortunately, there are a few simple things you can do to get rid of the smell:

  • Open your windows for several hours and run the AC on recirculation to get fresh air flowing through the system.
  • Sprinkle baking soda into each vent opening. Then use a damp cloth or a vacuum with a hose attachment to wipe away the baking soda and any mold growth.
  • If the smell is powerful or you notice visible mold growth, call a technician to disinfect your air ducts.

Can Mold In AC Make You Sick?

If there is mold in your AC, it can make you sick. The microorganisms mold produces, called spores, are tiny and airborne, and they settle in the mucus of your lungs. Once there, they can cause respiratory distress, including sore throat, wheezing, and coughing. 

Mold makes people sick by causing allergies and respiratory problems. These allergies can cause sneezing, coughing, watery eyes, and runny nose. They can also cause asthma attacks. People with asthma are expected to have severe reactions to mold exposure.

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