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Why My Air Conditioner Smells Musty?

by Remi Lavana
Why Air Conditioner Smells Musty

If you’ve ever turned on your air conditioner only to be greeted by a musty smell, you’re not alone. You wonder, why on Earth does my air conditioner smell bad? Does this mean more savings going down the drain? Well, that’s true! This is a common problem that can be caused by a variety of factors. The smell could be of anything, such as wet socks, something burning, or even a smoky odor. Let’s go over some of the most common smells that AC owners may encounter. In this blog post, we’ll explore seven common reasons why Ac smells musty and how to get rid of the smell.


7 Reasons Air Conditioner Smells Musty and How to Get Rid of It

If your ac smells musty, there are a few possible reasons that could have happened. Let’s discuss them one by one in detail.

  • Is Your Air Conditioner Smelling Like a Car’s Exhaust?
  • Do your AC vents smell musty or moldy?
  • Smells Like Sulfur
  • Does the air conditioner have a cigarette smoke smell?
  • Do You Smell Gas and Feel Like There’s a Skunk in the House?
  • Smells Like Dirty Socks/Stinky Feet
  • Smells Like Something Is On Fire

1. Is Your Air Conditioner Smelling Like a Car’s Exhaust?

One of the most frequent and possible reasons for this odor is a line leak of your Ac refrigerant. As its function is to absorb heat from inside of the house and enable the rooms to be cooled and it can lead to system functionality disability might leak and it looks like your air conditioning smells musty like a car’s exhaust. The refrigerant emits chemicals into the air as it performs its function. The chlorofluorocarbons (CFCs) in R-22 refrigerants, which were widely used for many years, are being phased out due to their dangerous effects. Check your system as soon as you can to see if it still uses R-22 and if there is a leak of refrigerant.

 How to get rid of this Musty air conditioner smell? 

To get rid of this ac smells musty and refrigerant leaks, have your local HVAC company top of the system’s refrigerant and repair its leak. Moreover, as a precaution, checking the refrigerant charge is another aspect of an annual tune-up — maintenance that’s critical to a well-functioning HVAC system.

2. Do your AC vents smell musty or moldy?

My ac smells like mildew and I don’t know why is that happening? Don’t worry! Plumbing and HVAC have found the cause why your Ac smells like mildew.  This is another most frequent and possible odor that most of the Ac owners face with their air conditioning system’s stale and musty smell. Mold and mildew could spread via the ductwork if the HVAC system has an excessive amount of moisture or humidity. The major reason is water buildup in the ducts, drip lines, or drain pipes, which can lead to the growth of mildew or fungus.

You can not only notice the stink coming from the leak but also observe water dripping out of your interior unit.

The smell might also be brought on by unclean air filters. If you turn on your air conditioner after a long rest period and live in a hot, humid region, moisture may build up in your filters and result in this musty odor.

 How to get rid of these moldy & musty AC smells?

If you’re having this problem, first professionally improve the drainage and have the AC lines and ducts thoroughly cleaned to get rid of the Air conditioner smells like mold.

But the best solution is to protect your belongings and avoid this problem from happening in the first place by replacing your air filters, scheduling annual or bi-annual AC tunes-ups & installing a dehumidifier. 

3. Smells Like Sulfur

Have the smell of rotten eggs spread in your home? Danger alert! It could be the smell of leaking gas from your air conditioner. 

When your air conditioner smells musty like rotten eggs, manufacturers are required to add a chemical named mercaptan to give it that distinctive rotten egg gas smell.  Another sign of a gas leak is a path of grass or shrubs that have changed to a sickly brown/orangish color

How to fix this Musty smell air conditioner?

For fixation of this smell coming through your vents, you need to do certain things. Don’t operate anything electrical, matches or lighters. Open your windows and doors and turn off your gas supply at the meter.

Still not sure what the smell is or if it is related to your HVAC system? Don’t hesitate to ask a professional.

4. Does the air conditioner have a cigarette smoke smell?

Eventually, If someone in your home has smoked, the odors could accumulate in the filter & evaporator coil and could be the reason for the musty smell air conditioning.

How can I get rid of the cigarette smoke smell in my air conditioner?

When you feel like your Air conditioner smell musty like a smoke fire, change the filter, get a professional tune-up and cleaning, and smoke only outside. The ideal option is to smoke outside, but you can also change your air filter on a regular basis and arrange an AC tune-up to get rid of the stench if it’s already there. Whatever the strange stench emanating from your system, you can never go wrong with contacting a professional to assist you to find out what’s wrong and make the necessary repairs.

Preventative steps such as changing air filters, scheduling annual maintenance, and installing indoor air quality devices will also be quite beneficial.

5. Do You Smell Gas and Feel Like There’s a Skunk in the House?

Feeling gas smell and skunk in your house?  This air conditioner smell is the most alarming one on our list. More often than not, this indicates leakage of gas within the system, specifically, Methyl Mercaptan. This ensures immediate detection to prevent any serious harm that can occur from gas leakage.  

You won’t be tricked if your air conditioner smells like skunk spray. This indicates that gas is seeping and entering your ducting. Turn off your gas supply as soon as you notice such a scent. As a next step, contact your utility company, which will determine the cause of the problem and rectify it.

Finding a solution? 

Well, the solution is not in your hands, and you will need to call your gas company to shut off your gas,  hire an HVAC professional to make repairs, and follow safety precautions. 

6. Smells Like Dirty Socks/Stinky Feet

The air conditioner smells musty like dirty socks and stinky feet? The reason is in front of you. It actually happens due to dirty air filters, evaporator coils, clogged condensate drain pans & stagnant water supply to your ac.

How to Get Rid of it?

To stop this ac smells musty, just replace your air filters every few months or hire a professional to clean the system or unclog the drain. Once it’s unclogged, add a few drops of distilled white vinegar to help destroy algae and fungi and reduce odors.

7. Smells Like Something Is On Fire

The final reason is why your AC smells musty like something is on fire. It happens when there is an overheating motor or wiring issue in your AC system. Alternatively, the smell may be due to dust settling in the unit after a period of inactivity. Once the AC is turned on after a long time, the dust can burn off and produce an unpleasant smell.

How can this problem be resolved?

If you smell burning plastic, gunpowder, or whatever else is on fire, switch off the system immediately and get an expert to come out and diagnose the problem. If you’re running the air conditioner for the first time in a while and suspect a dust buildup, you can wait a few minutes to see if the odor goes away. If the odor persists and the system begins to malfunction, turn it off and contact a local HVAC company.


You deserve to feel comfortable in your own home, and you should not have an air conditioner that stinks. Contact us if you need help with your musty smell air conditioner. We’ll diagnose the problem promptly and fix it throughout the competition.


Why does my ac smell musty?

Musty smells in the air conditioner can be caused by a number of things, from mold and mildew to pets and stagnant air. In some cases, the musty smell is just a sign that your AC needs a good cleaning. But in other cases, it could be a sign of a more serious problem, like a gas leak or a rodent infestation.

How to stop the musty smell from the air conditioner?

The air conditioner is one of the most vital pieces of equipment in the home, providing cool air in the summer and warm air in the winter. But sometimes, your AC can start to smell musty, which can be both unpleasant and dangerous. If you notice a musty smell coming from your AC, it’s important to investigate the cause and take steps to fix the problem. Otherwise, you could be putting your health at risk.

How to clean the musty smell from the air conditioner?

Blow compressed air far away from interior components to protect them. Fine dust particles in the unit’s front and back can be cleared using a brush or a tiny piece of cloth. Carefully clean the vent and duct with a cleaning solution, then flush the cleaning solution out with water.

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