Why does my heater smell?

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While it’s perfectly normal for a heater to emit occasional smells—especially the first time in use after a long summer of idleness—it’s important to note the type of smell, as some are more nefarious than others.


Some malfunctions in your furnace can cause odors like melting plastic or burnt rubber, mildew, rotten eggs, and even smoke. To keep yourself, your family, and your home safe, it’s important to understand why your heater smells and what to do about it.

Beware of These 4 Heater Smells

If you smell one of these odors coming from your home’s heater, don’t ignore it. They are clear indicators that something within the HVAC system has malfunctioned and needs to be addressed.

1. Melting Plastic

If you’re ever wondering, why does my heater smell like melting plastic?” the answer is this: somewhere in your unit, plastic is melting. Never ignore a burning smell emanating from your heating system. Burning or melting smells could mean that your heater’s motor or electrical functions are getting far too hot for it to operate optimally. 


The smell of melting plastic indicates that something is overheating, creating a fire hazard. In this case, you should turn your heater off immediately so no further damage can occur and call in a professional HVAC specialist to identify and resolve the issue.

2. Mildew

A musty smell coming from your heater means moisture is building up somewhere within your unit. Excess moisture can easily lead to mold growth, which is hazardous to the health of anyone breathing the air in your home.


Exposure to air particles contaminated with mold or mildew can cause serious respiratory health problems. Have a specialist do a thorough cleaning of your HVAC unit to remove any dangerous molds or mildew to restore the safety of your home’s heating system. 

3. Rotten Eggs

If you smell rotten eggs coming from your heater, immediately evacuate your home and call the gas company to turn off service to your home. A strong sulfur smell in your home may indicate a gas leak, which can be extremely dangerous. A technician from the utility company should repair the leak immediately. To help prevent future gas leaks, it’s important that you get your heater regularly serviced by a professional HVAC technician.

4. Smoke

Your furnace may smell a bit off, like something is burning, for the first several hours it runs after a long period of idleness, This is caused by the buildup of dust within the system burning away. However, if your heater smells like smoke or burning beyond the first few hours of operation, or randomly begins to smell like smoke, there’s an issue you need to take care of immediately. At the very least, something is overheating and you should call an HVAC technician to repair the issue. Worse though, is that a fire has already started. If you smell or see smoke, leave your home immediately and call 911. 

Keep Your Home Safe

Avoid expensive repairs and dangerous gas leaks by scheduling regular heating maintenance with CroppMetcalfe’s 5-Star Technicians. We can diagnose and address a variety of heating-related issues to ensure you and your family are safe throughout the winter. Call or contact us online today!



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