The Furnace Smells Musty – What Now?

Winter in Ohio is brutally cold, and good heating is essential. A reliable heater will work hard to keep you toasty warm all winter, and it will let you know when something isn’t right. One of the most unmistakable signs of a furnace or HVAC problem is the smell

When a furnace isn’t used for a while, it will gather dust. This produces a dusty or burning smell from the furnace vent. The dust is blown out through the vents and lasts a few hours. 

However, if your furnace smells musty, you might have a more serious problem.

When the Furnace Smells Musty, What Does It Mean?

If your HVAC smells musty, it may have mold or mildew growing in it. Mold is a health hazard, and it’s no less dangerous in a home HVAC system. Mold causes significant health concerns, such as:


  • Allergies
  • Coughing or wheezing
  • Itchy eyes
  • Sore throat
  • Fatigue and flu-like symptoms


Mold needs warm air and a damp and dark environment to flourish. If your furnace air smells musty, look for leaks or puddles near the vents or mold growing on the ducts. Mold continues to grow until it’s removed from the furnace and ducts by a heating specialist. 

A qualified heating technician will clean out the mold, find the cause of the buildup and rectify it. Once the mold is removed, it will alleviate the musty smell from your furnace.

Other Smells

Not quite sure whether the smell is musty or not? Here are some of the other common furnace smells that might be a sign of a problem with your furnace:

Metallic Smell

If there’s a metallic smell in your indoor air, it signifies a wiring problem, an overheated motor, or a worn bearing. Shut the heater off immediately and call a heating specialist. Electrical problems with the system are a fire hazard and need prompt attention.

Rotten Egg Smell

The strong odor from your furnace exhaust of rotten eggs or sulfur requires immediate attention. 

Natural gas has no smell, so gas companies add a chemical that smells like rotten eggs to detect leaks. This odd smell coming from the gas furnace indicates a gas leak, a serious health hazard.

Not only is a gas leak dangerous to breathe in, but it could lead to an explosion. If you smell rotten eggs coming from your gas home HVAC, turn it off immediately, open your windows, and call a heating specialist. 

New Furnace Smell

A new HVAC or furnace will give off an unpleasant smell when you first turn it on. A new heater has a protective coating of oil on the heat exchanger and some parts to keep them from rusting. 

You may be wondering how long the new furnace smell will last. The good news is that it won’t last long. Let it run for a few hours, and the smell will dissipate.

Diagnosing Furnace Smells

Your heater will give off certain odors to indicate different problems. You may notice these odors more in certain rooms, such as a strong smell in the bedroom when the heating is on. 

Smaller rooms with less airflow will register the smells faster than large rooms with good airflow. Regardless, the odor emanating from your furnace or HVAC must be investigated. 

Hearn Plumbing Heating and Air has been in the heating industry for years and has extensive experience diagnosing and repairing furnaces and HVACs. Don’t ignore dangerous furnace smells. Call us today.

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