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Imagine you come home after a long, hot, humid day. You take your boots off, loosen your tie, and turn your AC on (you wouldn’t be doing the last step if you had the Cielo Breez Plus), but smell something awry.
A bad stench fills your room, forcing you to turn your AC off.
You wonder, why on Earth does my air conditioner smell bad? Does this mean more savings going down the drain?
In this post, we’ll go over some of the common reasons why you may have a stench erupting from your air conditioner. The smell could be of anything, such as a wet sock-like odor, something burning, or even a smoky smell.
Let’s go over some possible smells that AC owners are likely to experience and find out the reasons for their occurrence, along with their solutions.
Types of Air Conditioner Smells, Possible Causes and What You Can Do
One of the most serious things that homeowners have to deal with is bad AC smells. But the problem is that you won’t know if the smell is coming from your unit, what type of smell indicates what issue, or what does Freon smell like. And to deal with the problem, you need to learn about it first!
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We’ve explained in detail about every kind of smell that you can experience if you own an air conditioner. So let’s take a look:
1. Air Conditioner Smells Like a Car’s Exhaust?
An air conditioner does not run on an internal combustion engine. So, there is no reason why your air conditioner should smell like running car exhaust. However, your air conditioner does make use of some fluids, and when heated, they can smell like exhaust fumes.
A smell from an AC such as this most likely means there is a leak in your refrigerant line. A refrigerant is a cooling agent inside your aircon, and a leak can impact the performance of your air conditioning unit. Moreover, it releases chemicals into the air and thus can be hazardous for the environment.
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Freon, a chlorofluorocarbon, is a commonly used refrigerant used in your air conditioners, although it is being slowly phased out. Freon absorbs heat from the indoor air, which is released outside. But it can be really dangerous for the environment. Therefore, you should always be careful if you suspect there is a Freon leak.
Whenever you’ve read something regarding a refrigerant leak, you must’ve thought, what does Freon smell like?
A Freon leak would smell like sweet chloroform or, in simpler terms, just like your car’s coolant but with a sweetish odor. Even though it is an almost odorless gas, you can still detect the smell. But Freon, being heavier than air, does not linger around in the air for long, and drops down to floor level pretty quickly.
If your AC is emitting a chemical-like smell, you should get it checked promptly by a professional. A Freon leak can be dangerous, and a certified HVAC specialist will repair it in no time.
In the meantime, crack open the windows and make sure your home is ventilated. This will not only keep the smell out but also prevent any hazardous effects from the chemical leak.
2. AC Smells Like Something Is on Fire?
There are a lot of electrical components within your air conditioning unit—circuit boards, power wires, fans, and compressors, etc.
If your AC smells like burning gunpowder or plastic, it probably means any one, or even multiple of these components are in fact, burning. In this case, immediately turn your air conditioner off and consult your local professional for a solution.
Do not attempt to do a DIY with this sort of a problem; it can be dangerous.
Another more common reason for such an air conditioner smell is that dust can settle within your unit after a long period of inactivity. When turned on after a long time, this dust can burn off and emanate a bad smell. This is only temporary and is nothing to be too concerned about.
Though if the smell remains, the AC starts to malfunction or the smell is highly pungent, you must turn off your unit and give your local HVAC expert a call right away.
3. Are You Smelling Rotten Eggs From Your AC?
A foul or rotten air conditioner smell is usually the result of dead rodents or critters stuck in the AC. This is a characteristic and distinct smell that you surely cannot mistake for anything else.
Birds and insects can nest or take refuge in your ductwork and, unfortunately, get trapped in the equipment.
With time, these dying animals emit unpleasant smells. As soon as you turn your air conditioner on, it can discharge a foul smell into your home. Dying or stuck animals can also damage different components within your system.
If you have a ductless/central air conditioning system, lizards and other critters can sometimes go into your indoor unit and make for an unpleasant experience.
It’s best to always pest-proof your unit to avoid such a nasty scenario and having your AC smell like a carcass. You can always call a technician to help remove the dead animal, or you can fix this issue yourself!
You will need to locate the exact duct from where the stench is erupting, use a screw driver to remove the cover, and then carefully remove the carcass. It can be tricky if the dead animal is not in sight. Keep a torch in quick reach. Once removed, gently wipe the area clean and make sure it is dry. It is recommended to have your ductwork checked to ensure nothing is damaged and seal any entry points.
4. Do You Smell Gas and Feel Like There’s a Skunk in the 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.
Natural gas on its own has no smell, but utilities and gas distributors put in Methyl Mercaptan to provide a distinctive odor to it. This ensures immediate detection to prevent any serious harm that can occur from gas leakage.
If your AC smells a lot like skunk spray, you won’t be mistaken. This means that gas is leaking and getting into your ductwork. At the first sign of such a smell, immediately turn off your gas supply. As a second step, contact your utility, who will detect the source and repair the problem.
5. Getting a Moldy or Musty AC Smell?
A stale and dingy smell is by far the most common and foul smell experienced from ACs. If your AC smells musty, the general cause is the accumulation of water in the drain pan or drip lines (or ducts in case of ducted systems), which can cause fungus or mildew to grow.
In case of a leakage, you might even get visible signs in your indoor ductless unit, such as water dripping down your wall.
Another reason for such a smell can be dirty filters. If you live in a hot and humid climate and turn your AC on after a long period of time, moisture can accumulate in your filters.
You will need to contact a professional and get your AC’s lines and ducts thoroughly cleaned. This will only remove the unpleasant smell. In case of a leakage, the source will also need to be fixed to prevent further problems.
6. Air Conditioner Smells Like Cigarette Smoke?
If you smoke at home, then there are chances that your AC will eventually end up smelling like stale cigarette smoke. This unpleasant smell can cause allergic reactions and headaches.
Your evaporator coil and filter absorb the odor from cigarette smoke. As a result, when you turn on the air conditioner, the embedded tobacco particles are knocked loose and sent back into your home through the AC’s vents, creating an unpleasant atmosphere.
Like all other problems, this problem has a simple solution. To eliminate the old tobacco smoke smell from your AC vents, change your air filter once every 30 to 60 days and clean your AC regularly. You can also start smoking outdoors.
Be Sure to Take Precautions Before Doing a DIY
There are a couple of things to keep in mind while we are at it.
Never try to do AC repairs by yourself. Always call a professional to do the job for you. Electrical components and water do not mix well, and there is a high chance of electric shock. You would be making a wise choice not to experiment at such a time.
If you do feel qualified enough to do a DIY, be sure you have thoroughly gone over your air conditioner’s maintenance and operating manuals. Then collect the right set of tools for the job. Finally, turn off the main power supply to your AC and have proper personal protective equipment (PPE) at hand.
Moreover, do not try to mask the bad smell using an air purifier or freshener. It will only make things worse. Delaying proper repair work will only damage your AC more than it already is and perhaps lead to you buying a whole new unit altogether.
Why my air conditioner smells bad? Hopefully, now you have the answer to the question!
Be it ducted or ductless air conditioning, all the factors above make for an unpleasant experience. So, the next time you come home and experience an unpleasant odor, you know exactly what it could be and what you need to do to fix the problem.
33 Comments. Leave new
My unit smells like sweet chemicals.. but matenince say no freon leaks.. why’s it still smell and my eyes burn after a few hours and sick stomach
I really appreciate you talking about how a single interior part failure can cause an AC to cause some horrible smells. This might be exactly what happened to our unit, as it’s been stinking up the place quite a lot with a smell that reminds me of burnt paper. I don’t think I’ll be able to fix that all by myself, so I’ll go and ask for some help from an HVAC expert in the area.
My window unit smells like crap…literally when I turn it on and this is it’s first season..it’s new. I see nothing dead in it. Washed and cleaned all vents etc. What else can I do? I need help!!!
If your AC smells bad, 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.
At a certain time in the night gives a headache smells like raw sewage I have to turn it off and turn my air purifier on it gives me a headache and a sore throat what can I do. I am in an apartment I have change the filters
I have an Window AC it smells like some think like lizard🦎 or Rat is dead in there but when I open AC’s Cabinet Then Nothing In That
And then I service my AC with detergent but smell doesn’t gone and there is no leaking in AC
Plz Help me to solve this
Hi, the dead animal may be stuck somewhere in the system. Remove the front cover of your window unit and try searching for it using a strong flashlight. You can also call a technician to help locate and remove the dead animal.
The technician searched and there were no dead animals. Instead they said gas was low. After filling gas, the rotten carcass smell has only worsened. He has suggested that the coil has to be replaced. I somehow feel that there is nothing wrong with the coil as the cooling is perfect. Please suggest
I have a ductless split AC. It’s emitting dead rat or lizard smell. Technician checked and said that it was low on gas and filled gas. Cooling improved but the smell got worse. Now the technician says that Coil has to be replaced. I somehow don’t feel that the coil has to be changed as AC is working fine but for the bad odour. Please suggest.
Recently one of the rooms in my house as begin to smell similar to car exhaust. It has a window ac unit that provides the cooling. No where else in the house smells like this. What could be the cause? Do I need to have it checked out?
This smell most likely means that there is a leak in your AC refrigerant line. Do get it checked by a professional as refrigerant leakage can be due to some internal problem. Plus, the refrigerant releases dangerous chemicals which be hazardous for your indoor air quality.
Thanks for the reminder that burning smells are very important to watch out for when maintaining an AC unit. I’d like to look for AC repair services soon because I’d like to make the most of the current cold weather. Since I would not be using my AC for the weeks to come, I might as well get maintenance for it.
We got a new ac unit and new duct work a little over a year ago. Our house is on a slab so the unit is in the attic. We noticed a water leak on our bathroom ceiling and our ac guy found the source. It was a drain line that was clogged and running over spilling onto the insulation and dripping on the ceiling. He fixed that but shortly after begin noticing a foul, sour, musty smell throughout our whole house. I’ve checked every water source for leaks and found nothing. Could this be from that drain line in the attic and our ac unit?
Yes, if you didn’t find any other source, the previously clogged drain line is the likely culprit. Water accumulation in the drain lines can cause fungal or mildew growth, hence the smell.
We have window A C in kitchen,an have noticed food has some kind of taste we not familar with.could it be absorbing something from A C
Hi Gabby, if the AC has a noticeable odor, it can spread and affect how your food smells and tastes. Consider cleaning your air filters and AC coils. Also, make sure you are keeping with regular AC maintenance.
I have lived in 3 different places in the last year, and they have had new air conditioning put in. All of them have a bad odor, usually just after the compressor(?) shuts down. What can I as a renter do about it?
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My air conditioner smells terrible every time it first comes on. Musty smell, gross!! I’ve told my apartment manager the ducts need to be cleaned and they find every excuse possible to not do it. Now I’m seeing spots from what looks like a white liquid dried up on top of a table right under my living room air vent. Its dripping from condensation. Thats proof my ducts are obviously then full of mold!! And my dog and I have been sick for years living here. Allergies, rashes and my dog even started having seizures since living here. Only time he doesn’t have them is when he gets an antibiotic!! Thats not healthy and costs me a lot of money and stress.
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I find it alarming to learn that one of the reasons behind a smelly air conditioner is dust buildup or a burning internal component. I should share this with my uncle, who recently experienced this issue. This way, he could have a professional check his unit out for issues before it gets worse.
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Thanks for pointing out that it is entirely possible for fungi to grown on my AC if I’m not careful about its moisture levels. I’m considering to get AC repair services soon because my daughter recently had an asthma attack due to the musty smell of the unit we have at home. It’s a good thing that the weather is starting to cool down after summer so it would be okay to not use the AC until it is repaired.
I didn’t know that your air conditioner may smell stale if water has built up in the drip lines and has caused mold to accumulate. I remember my brother telling me that his living room smells strange whenever he turns his AC on in the summer, and he’d like to find a way to fix it before he hosts a dinner party next year. Maybe he should find an expert that will handle the problem for him.
Thank you so much for talking about why AC units can end up smelling like gas when needing repairs. I was beginning to think I was paranoid when I kept smelling a gas smell in my house after turning off things like my stove and my furnaces. Even after checking my garage, I still ended up smelling it, so I was really worried that it might have been too late and I would need some expensive professional help. After reading your article, I’ll make sure to find an HVAC contractor to help me figure out which of my AC units is causing this.