23 Apr. 19

Why does my air conditioner smell?


You may have been perceiving some foul odour in your home without knowing the source. Well, that foul odour could be coming from your air conditioner. Sometimes, as a result of several reasons, your air conditioner could start giving off a foul smell. This disturbs your enjoyment of the air con. You would either have to put off the air con to avoid the smell or to leave it on and struggle with the smell. Either way, none of these options allows you to derive maximum pleasure from your air conditioner.

Often time, we get asked to provide a cause for smelly air conditioners. To that end, we have highlighted several reasons that can cause your air conditioner to produce a bad smell. This article will carefully take you through how your air conditioner works. This will give you an insight into the factors that cause your air con to smell. It would further make it more convenient for you to fix the problem yourself. Before delving into the causes, let us help you understand your air conditioner system.

How your air conditioner works

Although you know that your air conditioner cools your home or office when it is hot, it is likely that you do not know how it works. For a perfect understanding of why your air conditioner smells, it is necessary to understand how your system works. One interesting thing you may never have noted is that your air conditioner and your refrigerator works similarly.

Your air conditioner makes use of chemicals that transform from gas to liquid and then back to gas. It pulls in humid air over its evaporator coil and uses the refrigerant to cool the air. Following this, it redistributes the air into your home. Your air conditioner has three parts that ensure for its proper performance. They are the evaporator coil, the compressor, and the condenser.

  • The evaporator coil allows for hot air to be pulled in and transformed into cold air. Everything regarding this process done by the refrigerant is carried out in the evaporator coil.
  • A condenser has the function of heat exchange. Its function is to condense a gaseous substance to a liquid state by ensuring that it gets cooled. Condensers are used in the heat exchange process of an air conditioner.
  • At the core of the cooling process lies the compressor. Its job is to ensure that the refrigerant is squeezed enough to raise its temperature and pressure. This makes the refrigerant exit as a hot gas.


Why does my air conditioner smell?

Some of the reasons why your air conditioner smells include:

1. It is too big

One of the most important things you should not handle casually when getting a new air conditioner is its size. Ensure that you get a professional to help with the fixing. Where this is not adhered to, it can result in complications.

If your air conditioner smells, it may be because it is too big for your home. When your air conditioner is too big for your home, the cooling cycle becomes quicker which hinders the process of dehumidifying air. This can foster the growth of mould on your system; a factor which carries with it a stale and disgusting smell.

2. The drain is clogged

Another common cause of a smelly air conditioner is a clogged drain. Ordinarily, the drain is designed to collect the condensation that drips off your cooling coils. It is expected that there should be a clear passage of water through the drain. When the drain gets clogged, mould is liable to grow in the drain thereby causing the emission of foul smell.

3. The cooling coils are dirty

You should know that your air handlers blow over the cooling coils. Over time, if your air conditioner’s cooling coils are poorly maintained, they can get dirty. This results in the circulation of a foul smell.

4. The air filter is clogged

Your air conditioner is designed with filters. These filters are usually made from fibreglass material or cloth. Through their little tiny holes, they serve the purpose of cleaning the air that goes around your heating and cooling system. When filtration occurs, the air is forced through the filter thereby causing contaminants to be removed from the air.

However, these filters are very likely to trap dirt and get clogged. This is why they need to be regularly serviced by bringing them out and cleaning them thoroughly.  For effectiveness, you can have a regular maintenance schedule. Where these air filters are not maintained, they collect contaminants leading to the circulation of a bad smell.

5. Cigarette smoke

Your air conditioner can also be giving off a foul smell as a result of the smoke. If someone has smoked in your house, it is possible that the smoke collects in your air filter. If this is the case, when you put on the air conditioner, it distributes the accumulated smoke.

You would have to perform proper cleaning to get the air filters well cleaned. If the smoke has affected the filters, you may have to change the filter as a whole.

6. Overheated wires

Knowing fully well that your air conditioner runs based on several wirings and connections, there could be instances where these wires could burn. An overheating occurrence or a wiring issue could lead to the smell of burning wires in your home.

A reasonable solution in this situation is to turn off the HVAC system and see if the smell stops.  If it does not, then you would have to place a call to the fire department to get professional help.

Firstly, put off the HVAC system as a safety measure. We would advise that you get an HVAC contractor to rectify the situation. They will conduct a thorough walkthrough of your wires and make sure that there is no mechanical defect.

7. A dead organism in your HVAC system

If an animal dies in your air conditioner, it creates a disconcerting smell that cannot be ignored. This is why you have to know how to check your air conditioner for dead critters. The earlier you can ferret out the source of the smell, the better for your unit.

8. The rotten egg smell

When you smell anything similar to the scent of rotten eggs, never ignore it.  It is imperative never to ignore this smell. This is because the smell of leaking gas is very similar to that of rotten eggs. There is a particular chemical added to the gas that gives off that smell. Call in your HVAC professional immediately.

9. When the aircon smells of dirty socks

Several factors can cause your air conditioner to smell this way. They include dirty evaporator coils, clogged condensate and so on. When there is inadequate filtration, a cloud of dust collects in your air conditioner which fuels the growth of mould and mildew on your evaporator coil. Therefore, when you perceive a smell of dirty socks, find a solution asap.

There have been arguments as to whether or not the dirty sock syndrome has health implications. Generally, the answer is no. However, this is not the case if you have asthmatic patients or allergic people living in your home. Mould and mildew which result from the dirty sock syndrome can cause health complications.

How to fix your smelly air conditioner

There are several steps you could take towards solving some of your HVAC problems. All you have to do is learn how your HVAC systems work. This would go a long way in putting you on the right track in solving your HVAC problems.

1. Clogged Drain

If your air conditioner is producing a foul smell, as a result of a clogged drain, you have to get the drain cleaned. Ensure that the drain is carefully removed so you can clean the contaminants. For the drain to properly function, it has to be free from contaminants.

2. Where there is a burning smell

As discussed earlier, a burning smell could be resulting from an overheating or a malfunctioning wire. As such, you should not take it with levity. If you perceive this kind of smell, then the advisable course of action is to put off the HVAC system and call the fire department. Do not try to perform any unnecessary fixes in such a situation especially if you are a layman with little or no understanding of how the AC works.

3. Where there is a rotten egg smell

We have discussed above that where you smell rotten eggs; it could be as a result of leaking gas. This kind of smell needs to be addressed with absolute care. In cases like this, you cannot afford to slip. Few of the steps you are advised to follow are:

  • Do not operate anything electrical during that time
  • Do not light a match or anything with a naked flame
  • Leave the doors and windows open so the smell can escape.
  • Put off any open flames if there are
  • Evacuate the building quickly and call the gas company.
  • Lastly, do not be the one to turn the gas back on, let it be done by your gas company.

4. Dirty Sock Syndrome

This syndrome is not a joke, and neither is it intended to humour you. When you smell something that seems like someone just pulled off their socks, there is a very high possibility that it could be your AC. Before you delve into solving this issue, it is essential to rule out some options. These are some things to be ruled out;

  • Be sure to have your drainage pans empty. In case they are not, ensure that you get them emptied.
  • Be certain that your air conditioner filter is providing proper filtration. If it is moist or wet, make sure you replace it.
  • Be sure to have all your drainage lines cleared. Excessive moisture can be a problem if you do not.

From here, we can move to how we can prevent and treat the dirty sock syndrome. For prevention, there are two methods that we advise;

  • Ensure that you use quality air conditioners: Mold, mildew and similar bacteria need dust to survive. Using a quality air conditioner ensures that dust does not accumulate in your system thereby putting you ahead of these bacteria hazards.
  • Use air purifiers: These air purifiers perform the function of ensuring that the air in your home or office gets purified. What they do is to quickly kill off bacteria and other contaminants, causing the air to smell nice once again.

5. How to treat dirty sock syndrome

One common way to remedy the situation is by cleaning your evaporator coils. This may not be the guilty component, but in most cases, it solves the problem. Use the following  steps when cleaning your evaporator coils

  • Turn off the air conditioner: As a matter of safety and precaution, always start your maintenance process by putting off your HVAC system. Also, ensure that you put off your circuit breakers.
  • Get your water and soap ready, or a bleach solution. Also, have a brush with you for a job well-done. Wear safety goggles as a matter of precaution.
  • Locate your evaporator coil: In doing this, you have to understand the peculiarity of your air con to accurately know the location of your evaporator coil. The evaporator coil should be located inside the inner compartment of your AC.
  • If you find a cloud of dust or debris, the first step is to scrub it off. Then proceed to scrub the coil thoroughly. Scrub it thoroughly and yet carefully.
    This way, you can get your evaporator coils cleaned without spoiling them.


If the smell persists, it is an indicator of a deeper problem. In this scenario, you are advised to call in a professional. Thankfully, we have HVAC experts that can deal with your issue efficiently. Call us in today!