New Air Conditioner Smells – What To Do?

When temperatures rise, who wouldn't want to enjoy a cool breeze in the comfort of their home? Suddenly something spoils the mood; there's an odor coming from who knows where. As you search for the culprit, you discover that the smell is coming from your newly installed air conditioner. Fear not, as we will tackle the cause and how to fix it. 

There are multiple reasons why your air conditioner has a weird smell. Here are the scents that you'll encounter with a malfunctioning air conditioner, along with their causes:

  • Sulfur "Rotten Egg" Smell- Gas leak
  • Cigarette Smoke- Smoke accumulation in the filter
  • Must/Mildew/Mold-  Excess humidity
  • Gym Socks or Smelly Feet- Stagnant water inside the air condition unit
  • Dead Body- Carcass of a dead animal or pest inside your air conditioner
  • Sewage- Sewer gas leak to the drain
  • Burning Smell- Overheated plastic inside the air conditioning unit
  • Plastic Scent- Extended storage of the air conditioning unit, which is common in new units
  • Car Exhaust- Refrigerant Leak

We will also be sharing some helpful tips on how to improve your air-conditioner's performance and answer common questions.

Technician checking the wiring of the air conditioning unit, New Air Conditioner Smells - What To Do?

Reasons Why Air Conditioners Smell

Odors are usually warning signs of health hazards in your home. You may not realize it, but there's a chance that your air conditioner is not the problem. There might already be a current issue, and the air conditioner magnified the smell to the point where it grabbed your attention. 

Here is a list of possible reasons why an air conditioner smells foul:

Sulfur "Rotten Egg" Smell

Don't take this lightly. Unless you have a bad egg sitting somewhere in your house, a rotten egg smell usually means a gas leak. Gasses are hard to detect because they are typically odorless or colorless. Manufacturers add mercaptan to gas, which emits a distinctive rotting smellfor safety reasons. 

Another sign of gas leaking is when plants turn brown or orange-ish in color. Keep an eye on your grasses and shrubs since these are usually the first types of plants to change hue. In case of a rotten egg smell, follow the steps below.

  1. Do not operate anything electrical. Immediately, turn off your circuit breakers.
  2. Don't light a match or candle. If there are open flames within your vicinity, put them out.
  3. Open all doors and window to air out your surroundings since gasses are usually toxic.
  4. Turn off your gas meter. If you cannot do so, call the gas company and ask them to do so.
  5. Please have anyone inside evacuate the building.
  6. Contact your local fire department and gas company. Have them inspect your gas line and request a welfare check on your neighbors.

Cigarette Smoke

Do you have a brand new AC but are baffled because it has a tar-like smell? Try to remember if someone in your household recently smoked a cigarette. If yes, the smoke most likely accumulated in the AC's filter and evaporator coil.

The best solution for this is to change the filter. We're confident that you have experienced being in close proximity with a smoker, and the smell of cigarettes stick, right?

Usually, the only way to remove the odor is by taking a bath and changing clothes. The same goes for your AC filter; replace it with a fresh one, air out the room, turn it on, and you are good to go.

AC units include manuals on how to replace filters. There are also tutorials on the internet, such as the video below. You may also consult with a professional for a tune-up and deep cleaning.


Mold growing on the wall

Excess humidity, moisture, and exposed earth may cause mold and mildew to bloom in your AC's system. To prevent this from happening, you may want to install a whole-home dehumidifier that removes excess moisture and deposits the condensate outdoors.

Schedule time to execute a deep cleaning, fine-tuning, and bi-annual inspection to help maintain the cleanliness of your condensation drain line and evaporator coils.

You will notice a greenish-black accumulation on the pipes and ducts if a mold infestation happens.

Gym Socks or Smelly Feet 

Worker spraying light mist of water on the air conditioner

All air conditioners work by converting hot air into cold air. This process leads to condensation and the formation of tiny droplets of water inside the air conditioner. Any stagnant water can cause fungus and bacteria to grow inside the AC unit. Deep cleaning will resolve a smelly feet odor if there is a mold problem.

Here's a video showing you how to clean your air conditioner:

Dead Body 

This issue should be the last possible cause if your AC unit is brand new; it would be unlikely that an animal crawled inside and died there. If this happens for some unknown reason, open your doors and windows for ventilation,  contact your supplier, and ask for a replacement or refund. 

If you have a pest problem in your house, contact a professional pest management company and have them handle necessary repairs.


Sewer gases will leak up from your drain due to dry P-Trap. Manufacturers design P-traps to block sewage gas from escaping with water. To alleviate this problem, pour water down the drain to restore the water barrier in the P-trap. 

If this problem persists, you may have a backed-up sewer line or a damaged sewer vent pipe. Contact your plumber and have it fixed. Sewage gas is toxic and can lead to serious health problems if there is exposure for a prolonged period. 

Here's a great video showing you why you need a P-trap:

Burning Smell

If you smell something burning, then something probably is. The most common cause for this unexplained odor is overheated plastic in electrical components, whether overheating motors or faulty wiring. Whatever the source is, immediately shut off your circuit breaker.

A gun powder scent indicates your AC is experiencing a short-circuit. Also, burning plastics may sometimes emit a fishy or rotten egg smell. 

Plastic Scent

A mini split air conditioner in the living room

It is typical for new air conditioner units or most appliances to have a plastic smell. The plastic smell is due to being in  storage for an extended period. The scent is not strong enough to cause harm and will usually dissipate in one to two weeks.

Take the unit out of its packaging, leave it in an open space or area with proper ventilation for a week. Wait until the plastic smell weakens as the days pass.

Remember that a plastic scent is different from a burning plastic smell. The former has a mildly offensive and tolerable odor, while burning plastic emits a rotten fishy stench.

Car Exhaust

Worker checking and diagnosing the air conditioning unit

Air conditioners run on electricity and not on an internal combustion engine. So, there's no reason for it to smell like a car's exhaust. However, refrigerant cooling liquid may smell like exhaust fumes when heated. This smell hints that there's a leakage in your refrigerant line, which affects your AC's performance. 

Freon is the most commonly used refrigerant. In case of a leak, seek help from an expert because this should be quickly contained. Freon can be dangerous to humans and the environment.

Precautions Before Doing DIY

Hiring a professional may cost you hundreds of dollars, but that's a thousand times better and safer than engaging blindly with an electrical component attempting to DIY. A minor error with the AC system can lead to electrical shock; you shouldn't risk experimenting.

If you feel you can fix your AC unit's problem, these tips may prove helpful.

  • Have someone on standby to assist you with the repair.
  • Make sure you have read the operating manual twice over.
  • Have the right set of tools for the job.
  • And for the most crucial tip, turn off the air conditioner's main power supply and wear personal protective equipment.

Do Not Mask The Smell

Do not try to cover up smells with fragrances using air fresheners, perfumes, or scented candles. You want to have a lovely smelling home, but you're only making things worse. The aromatics mixed with the foul odor emanating from your AC will make it too overwhelming to breathe. Doing this might eventually lead to asthma, nausea or allergies. 

Spare yourself potential health problems and attend to the matter at hand. Delaying getting repair work done will only damage your AC more than it already is. If inclined, you may want to buy a whole new AC unit.


Technician checking the wiring of the air conditioning unit

New and older air conditioner units require regular cleaning and maintenance. Doing this will ensure your air conditioner's outstanding performance and smooth operation.

As the saying goes, prevention is better than cure. Tune-ups and inspections will save you from the hefty repair prices and allows you to maximize the valuable years of any appliance. 

If you found this helpful, try reading these other articles!

Share this article

One comment

  1. I googled to find out if refrigerant has an odor and I cannot get a straight answer online. My ac guy says no and 99% online say yes. So what is the correct answer and what does it smell like if it does have an odor.

Leave a Reply

Your email address will not be published. Required fields are marked *