Why Does My Air Conditioner Smell Bad?

“Is your AC stinking? Learn why it happens and what to do with it.”

Have you ever noticed a bad stench in your room as soon as you switched on your air conditioner? This foul smell seems to get worse if you keep your unit running.

When a foul smell begins to erupt from your AC unit, it is probably a warning bell that your system needs a cleanse and professional service.

Some smells are toxic and require immediate attention. If left unattended, it may be harmful to health.

Wondering how to identify these smells and eliminate them? In this article, we will discuss in detail the reasons for their occurrence, and the possible solutions to alleviate this issue in your home at the earliest.

Table of Contents

Why Does My Air Conditioner Smell Bad: Causes & Solutions?1. Bad foot odour or dirty socks 

2. Rotten Eggs

3. Mold or Mildew

4. Exhaust Fumes

5. Burning Smell

6. Skunk Smell

7. Cigarette Smoke

Can I Deal with Odour-Related Problems at Home?


Why Does My Air Conditioner Smell Bad: Causes & Solutions?

Before we take a deep dive into the causes and solutions, let us analyze the different AC smells in the first place:

Smell TypeProblemSolution

Dirty SocksDirty or Clogged Air ConditionerProfessional Service & Full Cleaning

Rotten EggDead Animal in Air DuctsCall a Technician

MustyMold or MildewCall a Technician

Exhaust FumesLeakage of Unit FluidsCall a Technician

BurningShort CircuitCall a Technician

SkunkPossible Gas LeakageCall a Technician

CigarettePossible Cigarette SmokeReplace the Air Filter

1. Bad foot odour or dirty socks 

If you notice the smell of stinky socks or feet from your unit, then the culprit is a dirty or clogged condenser of the air conditioner. This is primarily because the condensing drain line gets clogged with standing water that stays stagnant and does not drain, leading to a stench.


The only solution to get through this is a thorough cleaning and a professional service.

2. Rotten Eggs

Are you noticing the smell of rotten eggs from your AC? This indicates that there is a dead animal inside the unit. When any insects or birds that take shelter in your air ducts get trapped inside, unfortunately, they die and decompose. Whenever you switch on your air conditioner, it discharges the unpleasant or foul odour into your home.

Sometimes, lizards and other animals can get stuck in the different components of the AC system, making it a horrible experience for those inside the room.


The best solution to address this issue is to get your air ducts cleaned thoroughly. Doing this will help you get rid of the nasty smell and also the animal remains if any.

3. Mold or Mildew

This is probably one of the most common foul smells that many of us experience from our ACs. If your system smells like mildew, it is a clear sign that mildew or fungus is growing in your air conditioner.

When there is excess moisture in your unit because of the clogged drain pan or drain line, it leads to mould and bacteria growth. The mould build-up will cause your system to smell musty or mouldy.

Another contributing factor could be the dirty filters. Your filters can accumulate moisture inside if you have not switched on the AC for a long time. This issue is more pertinent for those living in hot and humid areas.


A musty smell is not a serious problem. However, it can eventually affect the air quality, further increasing the risk of respiratory illness in children and adults.

To ensure the high quality of air inside your home and your family’s health, opt for a professional cleaning. Call for an expert technician who has the knowledge to handle mould, fungus, or any bacteria growth.

4. Exhaust Fumes

Did you ever notice the smell of exhaust fumes or gas from your air conditioner? Many misinterpret the situation as gas leakage from the system and often get worried. However, what many fail to realize is that their air conditioners do not run on gas.

When your AC unit smells like fumes, and if you are worried about where this could be coming from, then a fluid leakage is the only reason. When the fluids or coolants leak from your air conditioner, it triggers the discharge of a bad smell.

The fluid leak can be dangerous to health. Whenever there is a refrigerant leak, it releases chemicals into the air, which can be hazardous for the environment.


The safest way to tackle this issue is to call a professional who can handle this situation. You can prevent this by having regular maintenance of your AC. We recommend you not to take the situation lightly as it can be dangerous in some circumstances. So, act swiftly and promptly.

Meanwhile, we suggest you keep the windows of your home open to ensure proper ventilation. This helps in keeping the smell out and also prevents any serious consequences from the chemical leak.

5. Burning Smell

If it smells like something is burning inside your air conditioner, then it probably is. Your system has many electrical components inside, and a burning odour indicates the failure of these components or wiring issues.


If your AC smells like burning, switch off the unit immediately. After turning off, call a professional immediately to check for the concern and fix what went wrong. Do not try to sort this problem all by yourself as it could be dangerous.

Sometimes, when your air conditioner is inactive for a long period, dust can get accumulated in your unit. When you switch on the AC after a long time, this deposited dust can get brunt and emits a bad smell.

6. Skunk Smell

If your notice a skunk smell from your air conditioner, then this is something very alarming. Do not ignore a skunk-like odour because there could be gas leakage in your system. Methyl mercaptan is that gas with a distinctive odour responsible for the skunk spray. Whenever you notice this strong pungent smell, it is a clear indication that this gas is leaking and getting into your unit’s ductwork.


This is a flammable gas that can pose a risk to your family. When any instance as such, turn off your gas supply immediately and evacuate the home. Contact a professional without any delay to detect the problem and address it as soon as possible.

7. Cigarette Smoke

If your AC room smells like cigarette smoke there are chances that someone smoked inside the home. The filter and evaporator coil absorbs the odour from the cigarette smoke, eventually making the entire room smell like one. This may create an unpleasant atmosphere in the room.


To eliminate the smell of tobacco from your room, we advise you to change the air filter at least twice a year, i.e., in winter and summer. Ideally, it is for every 90 days.

Make it a habit to smoke outdoors.

Can I Deal with Odour-Related Problems at Home?

Dealing with your air conditioner’s odour-related problems is entirely dependent on the kind of odour. While cleaning or replacing the filter will suffice, it is advisable not to do it by yourself. However, you can prefer servicing or changing the filter on your own, provided you have a general practice.

Never try to cover these smells in your home by using room fresheners, sprays, scented candles, or others. These will only worsen your air conditioner and lower the air quality. To save yourself from nausea, headache, breathing difficulties, and other health issues caused by the AC foul smell, calling a professional is the best bet.


If you are not sure of what is causing your AC to stink, this article might help you to detect the smells and also the causes behind them. Seek the help of a professional who not only helps you get rid of any nasty smell but also checks for similar problems.

If you find this information to be useful, do let us know in the comments section below. If you have any other questions on the same, you can post them as well. We would be happy to help you.



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