What’s That Smell Coming From My Furnace?

bacteria causing a smell coming from the furnace

If your furnace is producing a strange smell, you should always treat it with caution. While the cause for the odor may be benign, it could just as easily be harmful to inhale. When in doubt, always open windows to ensure ventilation, and evacuate your Tennessee home.

For your convenience and protection, our Kimbro Air team developed a list of five common furnace smells and what they mean.

1. Burnt Plastic

If you just turned on your furnace for the winter, your nostrils may detect a burning smell. If this is the case, you don’t need to panic yet. Furnaces collect dust over time, which is burnt off when you first turn on your furnace. 

It might be a good idea to check your filter to see if it needs replacing. However, if the smell doesn’t dissipate after about 30 minutes, contact one of our heating, ventilation, and air conditioning (HVAC) professionals to check it out.

2. Rotten Eggs

The sulfuric rotten-eggs smell usually points to a natural gas leak. Gas distributors often give it this smell in order to tip you off when a leak occurs, since gas is typically odorless. 

If you believe there is a natural gas leak, open your doors and windows, then be sure everyone gets out of the house to safety. From there, you should call 911 as well as your Hendersonville gas company.

3. Musty and/or Mildewy

This smell is usually indicative of dirty air ducts. Over time, your ductwork becomes overrun with dust, debris, mildew, and mold. Your home’s ventilation carries this smell throughout the house. 

Not only is this smell unpleasant; it’s bad for your indoor air quality (IAQ). Indoor air quality can be decreased by several contributing factors. According to the US Consumer Product Safety Commission (CPSC) , most homes have more than one source that contributes to indoor air pollution. To solve the smell issue, have your ducts cleaned by a professional.

4. Metallic and/or Electric

This is likely the smell of your motor overheating. In this case, it’s a good decision to power down your furnace immediately. Then, schedule a repair with one of our professional  technicians.

5. Formaldehyde

If you can smell a pungent chemical smell similar to formaldehyde, this presumably means you have a cracked heat exchanger. You should evacuate immediately and call 911. Cracked heat exchangers are known to release carbon monoxide (CO) fumes that are potentially lethal when inhaled.

Contact Us for All Your Furnace Needs

Our team at Kimbro Air hopes you found this list of common furnace smells useful. Remember, always treat chemical smells with the utmost wariness. Call us at 615-824-8098 or request service online here in Hendersonville,TN, or any of its surrounding areas with any additional questions or to schedule service.


Kimbro Air proudly provides HVAC service to Hendersonville, Nashville, Bellevue, Bordeaux, Brentwood, Franklin, Gallatin, Goodlettsville, Hermitage, Madison, Mt. Juliet, White House and the surrounding communities. Visit our service area page for more coverage details, call us at 615-824-8098, or request service online today.

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