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From A.B. May
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From A.B. May

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5 Reasons Why Your AC Smells Bad

AC smells bad

Imagine walking into your home and smelling a terrible odor. Your AC is running, and the smell is now circulating throughout your home. It might be stronger in one room compared to others. You look around your home, trying to find the source, realizing it is permeating everywhere. That’s when you realize it might be coming from your air conditioner.

If your AC smells bad, there could be a handful of issues causing it, and it’s something you need to get taken care of as soon as possible. Whatever is causing the smell could make you or your family sick, wreak havoc on your AC system, and cost you a lot of money to fix if it’s not taken care of right away.

Let’s look at what happens when your AC smells bad, what the different smells might mean, and how to get your AC smelling good (well, maybe just cool) again.

Reasons Why Your AC Smells Bad

Exhaust Fumes or Rotten Eggs

If you smell exhaust fumes or something that smells like gas, first and foremost, open as many windows as possible and exit your home. Call the fire department and the local gas company you do business with and report a possible gas leak. While most AC units aren’t powered by gas, some are, and it may be an issue with the fluids used leaking into the airflow of your HVAC system. A rotten egg smell, also associated with gas leaks, can occur when rodents or small animals die in the ductwork.

However, your AC may also be circulating gas if other appliances or the gas hook up to your home is experiencing a leak unrelated to your air conditioning. This is why your first call if you smell exhaust fumes or gas is to the gas company and fire department – not A.B. May. Call us if it’s not a gas leak after checking with local authorities.


A skunk’s scent is never pleasant. It makes everyone panic that they’re going to get sprayed. Luckily, or unluckily depending on how you look at it, if you smell a skunk from your AC vents, this may indicate a gas leak. We recommend following the above recommendations for exhaust fumes or rotten eggs before calling A.B. May to investigate.

Burning or Gun Powder

If you smell burning from your AC vents, turn off your unit immediately. Check your home for any signs of the stove or oven being left on or any other signs of a potential fire. If you suspect something like this, call 911. If you don’t see any signs of a fire, open the HVAC closet or head down to where your indoor unit is and take a whiff. If you can smell burning or gun powder from the unit, chances are the circuit board or fan motor has or is in the process of shorting out.


Mildew is the most common culprit when an AC smells bad. If you smell moldy air coming from your AC vents, mold or fungus are growing in or around your AC unit and can sometimes make their way into the ductwork itself. This is common, especially in humid environments, where mold or fungus thrive in warm, wet weather conditions. If the moisture being pulled into your AC isn’t drained properly, it eventually will seep into your AC filter and start making your home stink.

This is a situation where, yes, change your AC filter, but that’s probably not the core of the issue, and you’ll need our HVAC technicians to come out and see why your AC smells bad.


We’re not kidding here. If your AC smells bad and it smells like feet, you’re most likely dealing with an extremely dirty and clogged-up air conditioner. This typically starts with an AC that’s not draining properly so that water and all the dirt and debris within it starts pooling up and festering. The feet smell comes from that.

Can You Do Anything About AC Smells?

There are a few things you can do to reduce your AC pushing different smells through your home:

  1. Change your AC filters based on manufacturer guidelines.
  2. Install an air purifier if your HVAC system allows it. If not, have A.B. May make a recommendation on an air purifier system that will work.
  3. Use exhaust fans when cooking, cleaning, and showering. This will help release chemicals and other smells outdoors instead of letting them get into your vents.
  4. Consider the types of household cleaners you use. Anything with a toxic smell can and will make its way through your home.
  5. Wipe down counters, appliances, dust, vacuum, and regularly sweep, as well as wash your linens and towels regularly to keep smells and debris from getting moved around your home by your AC.
  6. Schedule annual maintenance to ensure your AC is performing at peak efficiency.

What Should You Do If Your AC Smells Bad?

Like every AC issue that pops up, our first recommendation is to change the filter. This does help with a variety of issues, including bad smells. If the smell persists, it’s time to call A.B. May to come out and diagnose what’s going on. We recommend annual maintenance and will work with you to determine the best scheduling for your home. Call us today and see how we can keep your home smelling good and keep the temperature cool during the summer.

Read More: Why is the AC Not Working in My House?

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