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What Is That Weird Smell Coming from My Furnace?


Furnaces are designed to circulate fresh, clean air throughout your home, so when the air coming out of your vents has a funky odor, it won’t go unnoticed. Whether the odd smell is faint or completely overwhelming, it is important to understand what is causing it.

Diagnosing Your Weird Furnace Smell

Strange smells coming from your furnace are often an indication that something is wrong. To avoid a complete furnace breakdown, you’ll need to figure out what is causing the odor and have it addressed by a team of professionals right away. Continue reading for help diagnosing your weird furnace smell.

Rotten Eggs or Sulfur

The smell of rotten eggs or sulfur when your furnace is running is often caused by a failed heat exchanger. This can result in a gas leak and the release unsafe levels of carbon monoxide into your home. Because natural gas often has no odor at all, gas companies actually add the scent of sulfur as a safety precaution.

In addition to the smell of rotten eggs, a gas leak is often accompanied by the following symptoms:

  • Nausea
  • Fatigue
  • Dizziness
  • Troubles breathing

If you believe you are experiencing a gas leak from your furnace, turn it off, open your windows to let fresh air in, contact your gas company, and schedule furnace repair at once.

Dirty Socks

During cooler seasons, the coils on your furnace will cool as the temperature outside drops and then become warm again when you turn the heater on. This fluctuation between warm and cold can actually foster the growth of bacteria in your system, which can cause your air to smell like dirty socks.

Burning Dust

It is completely normal to smell burning dust when you turn your furnace on for the first time this winter season. If you’ve changed your filter and the smell persists for longer than a few days, however, you might have a problem on your hands.


If you can smell smoke coming from your vents, turn your furnace off immediately and open your windows to let fresh air in. This is usually caused when the exhaust vent in your furnace malfunctions and stays closed. The combustion exhaust from your furnace is then forced through your duct system, sending the smell of smoke through your home.

Electrical Burning

If the air from your furnace smells like singed wires or burning rubber, it is likely that a component in your system is overheating and needs to be replaced.


If you’ve just turned your furnace on for the first time season only to notice that the air coming from you vents smells rather musty, it is possible that there is mold growth within your ductwork.

Bring in the Professionals

When your furnace is acting up, it’s time to call on the professionals. Since 1944, Bay Heating & Air Conditioning has been the leading HVAC company in the area. Serving both residential and commercial customers, we have the tools, training, and technology to quickly get to the bottom of your furnace problem and implement a fast, effective repair. Our NATE-certified technicians are familiar with all makes, models, and brands of equipment and guarantee that we can have your furnace functioning properly again in no time. And, you can rest easy knowing that we are always committed to the Bay Comfort Promise: to do everything possible to ensure you have a comfortable home or business.

For assistance with your furnace, call Bay Heating & Air Conditioning at (440) 294-4954.