Why Does Your Furnace Smell? – 5 Reasons for Furnace Odors

Switching on your furnace should only cause you and your family to start feeling warmer and cozier. It should not cause you all to start curling and plugging your nose. If running your furnace causes your home to start smelling foul, then there could be a serious problem with your heating system that needs professional attention sooner than later.

5 Bad Yet Surprisingly Common Furnace Smells

Dust: Running your furnace for the first time in months – like for the first time of the winter season – can cause the smell of dust to start circulating in the air. It might even smell like the dust is burning. You might be able to guess it, but this smell is actually caused by burning dust. As months go by without use, your furnace starts to collect dust, as all things do. Switching it on will cause the dust to circulate and even burn up if it gets hot enough. This smell is extremely common and should take care of itself after a few hours of use, so you don’t need to worry too much about it. If the smell of dust sticks around for days, though, there could be an issue with the furnace’s motor that will require some fixing.

Dingy laundry: If it smells like old laundry when you turn on your furnace, then there could be a bacterial colony growing in your furnace. The bacteria become heated by the furnace, creating the fetid, musty smell as it circulates through the air. Bacteria in a furnace and air ducts are difficult to clean without the help of a professional with industry tools.

Burning plastic: The unusual yet unmistakable odor of burning plastic is not something you should smell when you turn on your furnace. This smell is almost guaranteed to be caused by a small electrical fire within the furnace, like a wiring defect. The furnace’s motor could also overwork itself, causing a spark that makes an electrical fire that smells of burning plastic or metal. Shut off your furnace immediately if you notice this smell and call for emergency HVAC services. Do not leave the furnace unattended while you wait for the technician. If the fire produces noticeable smoke or visible flames, please take immediate action to extinguish it with an ABC fire extinguisher or call the fire department.

Smoke: Sometimes a furnace can produce an unusual smoky odor. This smell is caused by oil in a gas-based furnace igniting in an unusually large amount or outside of the furnace’s combustion chamber. Oil that spills while refilling your furnace’s oil tank can also evaporate the next time the furnace is used, which is usually not a problem. As with the smell of burning plastic, if the smoky smell does not dissipate soon, you should shut off your furnace and call an HVAC technician for immediate assistance.

Rotten eggs: Out of all of the smells on this list, the stench of rotten eggs is the most alarming, as it could indicate a gas line leak. If your furnace uses gas as an ignition source, then that same gas could leak out due to a system defect or damage. Gas companies lace the gas they provide with a chemical call mercaptan, which stinks of sulfur, i.e. rotten eggs. Otherwise, you would not be able to tell if there was a gas leak since natural gas is odorless and colorless. If you smell gas in your home, evacuate all people and pets as soon as you can. Only try to open windows and shut off your furnace if it is absolutely safe to do so. Call the fire department for help shutting off the gas before calling an HVAC company to come look at your furnace.

The Right Company for Bad Furnace Smells

Is your furnace acting up and emitting a foul odor that won’t go away? Call (216) 202-3778 and connect with Arco Comfort Air in Cleveland, Ohio. Our HVAC technicians are here to help keep your home safe and your family comfortable by providing comprehensive, competitively priced furnace repair services, including same-day services in a pinch.