Bad smells emanating from the AC are never a good sign, and finding a quick and efficient solution is crucial. 

If you live in Ambler and are facing strange scents from your AC system, the first step is diagnosing the smell. Here are some of the nine most common odors we encounter and how to fix them.

Smelly Cigarettes

Cigarette smoke is a strong and lingering odor. If you, or a previous resident in your home, smoke the residue from carcinogens gets stuck in the HVAC filter. It also sticks to surfaces like AC fins and even ductwork.

Problem: Smoky filter

Solve: change your filter regularly. For smokers, this should be every 30-days or more if you notice the filter changing color through the month. Cigarette residue leaves a yellow color on whatever it clings to, making it easy to spot.

Funky Gym Socks

You read that right. Sometimes AC units give off a funky sock smell. Just like your gym socks, the cause of the odor is bacteria.

Air conditioning units deal in water, and water helps bacteria grow. Your AC unit then blows this bacterium through your home, yuck!

Problem: Bacteria in AC water

Solve: Again, the filter should be changed to remove excess bacteria from the system. Next, the AC unit should be thoroughly cleaned. The evaporator coil and drain are likely to be the largest point of concern with this odor. Ideally, your annual HVAC maintenance will prevent the gym sock smell.


Sulfur has a terrible rotten egg-like smell. If your AC suddenly smells eggy, contact the local authorities. A gas leak is a likely culprit, and it could be quite harmful, especially if flammable.

Problem: Gas leak

Solve: Turn off any gas in your home, exit the building, and contact the local authorities. They will direct you on the next steps to take.

Mold or Mildew

A musty earthy smell coming from an AC unit is likely mold or mildew growth. Like the funky sock bacteria we mentioned above, this is caused by moisture. Unfortunately, mold is tough to get rid of on your own because once it begins blowing through the ductwork, it could be anywhere.

Problem: Mold in AC unit

Solve: Clean or change AC filter and contact HVAC specialists to have the unit and ductwork cleaned.

Sweet Chemicals

Don’t let your nose fool you into thinking a sweet smell is something good. Like vehicle coolant, which leaves a sweet odor caused by treated ethylene glycol, AC refrigerant is dangerous. In fact, Freon is deadly when inhaled.

Problem: Refrigerant leak

Solve: Turn off the AC and open all the windows in your home. Leave your home and contact an HVAC specialist to drain the refrigerant and fix the leak.

Motor Oil

Another refrigerant-related smell is car fumes. Car fumes are typically caused by burning gas. In the case of your AC unit, it’s probably a motor issue or leaky refrigerant, or both!

Problem: Broken motor or leaking refrigerant

Solve: Turn the AC unit off and call your HVAC specialist for maintenance.

Acrid Burnt Toast

Burning smells are never good in the HVAC world. It’s likely that your motor has overheated or an electrical problem has occurred. You may not see sparks, but that doesn’t mean they aren’t there. A wiring issue or overheated motor both require outside assistance.

Problem: Electrical shortage or overheating motor

Solve: Turn off the AC unit. Head outside and contact the fire department if the odor doesn’t dissipate.

Rotten Food

Garbage odors are especially unpleasant for AC owners. The decomposing smell is likely exactly what it smells like—a dead creature. Small animals like mice, birds and even squirrels seek contained spaces to nest. If there’s an opening in your ductwork or AC unit from outside, it could attract unwanted visitors.

Problem: Animal in the ductwork or AC unit

Solve: Contact animal control for advice on how to handle the removal of the creature. Your HVAC specialist will also need to come to clean the unit. Turn the AC off in the meantime to prevent further spreading of bacteria and bad smells.

Skunky Smells

Believe it or not, sometimes skunks wander onto local properties in Ambler. The AC unit spooks them, and they spray. Unfortunately, this odor then permeates the unit and gets filtered into your home. So, that skunk smell you smell could be an actual skunk!

Problem: Skunk sprays AC unit

Solve: Turn off the AC unit and open the windows to clear the smell from your home. Have an HVAC specialist clean the outside unit before switching back on.

Contact Us for More HVAC Help

If you live in Ambler and are interested in learning more about keeping your HVAC clean, we’re here to help. Call PlumbPRO Services today!