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Why Does My Furnace Smell Bad?

HVAC technician repairing a gas furnace

When temperatures drop below freezing in the Puget Sound region, you depend on your furnace to keep your home comfortable and safe.

Learning to identify the signs of a furnace problem can help you avoid spending hours or even days without heat by preventing a breakdown in the first place.

Unusual smells are one of the leading indicators that you need heating repairs. Here are some of the most noteworthy odors that you should be on the lookout for:

New Furnace Odors

If your furnace was recently installed, you may notice an unusual smell the first few times it turns on. Some of the oil and other protective coatings are burning off, and it is perfectly normal.

Oily Odors

If your furnace smells oily, there may be a gas or propane leak. Replacing the fuel lines or burners will likely restore your system.

Smoky Odors

The smell of smoke usually means that your furnace has blocked ventilation. If the flue is blocked, a technician with the right tools can remove the blockage quickly.

Chemical Odors

Chemical odors like a formaldehyde smell indicate that the heat exchanger is cracked. This means you’ll need a furnace replacement, as the damage can allow combustion gases like carbon monoxide to enter your home.

Burning Odors

If you notice metallic, smoky, or burning plastic smells, there may be flue issues, loose terminals, damaged or overheated wiring, or faulty sensors.

Shut off the furnace and call a professional to inspect the flue and repair wiring damage or failed components.

Rotten Egg Odors

If your furnace smells like rotten eggs, there may be a natural gas or propane leak. Shut off the furnace, call your utility company to turn off the gas supply, and leave your home until the gas dissipates.

Then, have the gas leak repaired by a professional once the home is safe to reenter.

Moldy & Musty Odors

Musty, sour, or mold-like odors can indicate that your ductwork, heat exchanger, or evaporator coil may have been contaminated by bacteria or mold, which have the potential to cause illnesses.

Call a professional HVAC company for thorough duct cleaning and system tune-up.

Schedule Furnace Services in Kent, WA

If your furnace smells odd, isn’t heating well, or shows other signs of malfunction, call our HVAC experts at AAA Heating & Air Conditioning for help.

We serve the Puget Sound area, offering routine furnace maintenance to prevent breakdowns and help you catch potential problems early, as well as furnace repairs to solve any existing issues. We also offer emergency heating services for major problems like gas leaks or heat exchanger failures.

Our technicians are trusted, reliable, and expertly trained. You can always count on our team for upfront pricing, free estimates, and great customer care.

Schedule furnace repair or maintenance by calling AAA Heating & Air at (253) 234-1278 today. We service natural gas, propane, and electric furnaces from top manufacturers.

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Proudly Serving

Kent, WA and the surrounding areas


Kent | Auburn | Renton | Maple Valley | Ravensdale
| Covington | Black Diamond | Federal Way | Seattle
| Des Moines | Burien | SeaTac | Normandy Park |
Issaquah | Newcastle

View More