Why Does My AC Smell Weird?

Why Does My AC Smell Weird?

A healthy furnace or air conditioner won’t produce any strange odors when they kick on. In an ideal home, your HVAC system should instead provide fresher air that’s been filtered of contaminants. If you’re noticing fluctuating mustiness or sharp burning smells, something’s going wrong. Address these foul odors fast before their root cause is given the chance to spread or worsen. Here are a few common HVAC odors and what they may mean.

Mildew/Mold Smell

Air conditioners can struggle with musty odors if their evaporator coils freeze and begin dripping water into the system. Both central ACs and furnaces also have condensate lines and drain pans that should safely transport moisture to a drain. If this line clogs with mildew or your pan cracks, water will begin pooling inside or even around your system. Left unresolved for too long, the mold spores may spread to your filter or other parts of your heating and cooling system like your ductwork. In addition to creating an unpleasant odor, breathing in airborne fungal contaminants can harm your respiratory health and worsen your allergies.


A dusty or old smell is most commonly noticed at the beginning of the cold season when you first kick on your furnace. After a long summer of disuse, your system will immediately burn away the layer of dust that’s settled on its internal parts. This can create a faint and usually brief dusty odor. Another common reason behind stale air is a clogged filter full of particulates. HVAC filters should be changed every one to three months. Using an old filter for too long will cause unnecessary strain on the system and result in lowered indoor air quality.

Rotten Egg Odor

Heating systems powered by natural gas can emit sulfur or rotten egg smells. While natural gas has no color or odor, fuel providers include an additive so you can more easily identify a leak. This highly flammable gas can pour into your home if your system encounters an issue with the burners, pilot light or gas supply line. Older systems can also run into issues with their heat exchangers that may crack or develop holes due to rust or corrosion. If you believe you have a gas leak, you should turn off your main valve and evacuate the home.

Burning or Fishy Smell

Overheating is a common heating system issue that can come about from clogged filters. Without enough airflow, the temperature inside your system will rise to unsafe levels. This can melt the insulation around your wiring, causing a burnt or fishy odor. Continuing to run a compromised system may cause enough damage that you have to replace the system. Depending on where the issue occurs, there may even be a chance of a house fire.

Other Signs of Faulty HVAC System

Along with unpleasant smells, malfunctioning heating and cooling systems can decrease your indoor comfort and temperature control. You may find some rooms in your home are never comfortable no matter how long your system runs. Your equipment may cycle too often or refuse to respond to your thermostat changes. Failing furnaces and air conditioners also aren’t as efficient as well-maintained systems, meaning you’ll likely have higher energy bills every month.

To keep your HVAC system in peak shape, you should schedule expert maintenance with a professional at least once a year. Remember to regularly switch your filters and keep an eye on your system for changes in its functioning smells or sounds. Don’t neglect to call for skilled heating repairs and cooling repair if your HVAC system is acting irregularly. Many common furnace and AC issues begin small like a frayed wire or loose belt. The extra strain on the system will exacerbate the problem, making the equipment work harder. Repairs and other professional HVAC services are an investment in your systems’ lifespans and overall efficiency.

Quality HVAC Services and Craftsmanship

Beck Cohen is the oldest heating and cooling company in Charlottesville, VA. Since 1955, we’ve been dedicated to making our customers’ homes as comfortable and energy-efficient as possible. Our NATE-certified technicians can maintain, repair or replace your air conditioner, furnace or mini split. We excel at sealing ducts, improving your air quality and offering generator services. Be sure to keep us in mind when you need plumbing services like leak detection or repairs. Call our specialist team today to schedule your HVAC service in Charlottesville.