Why the Heater Smells Like Burning When It Turns On

Leah Lopez Cardenas
Updated May 27, 2022
The interior of a bedroom with a potted plant, a night table and a heater
Photo: alvarez / E+ / GettyImages

That funny odor coming from your heater could be a dangerous situation right under your nose (literally)

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If your heater smells like it’s burning when you turn it on, you’ll likely want to do something about it ASAP. While the cause could be something as simple as a dirty filter, it could also be a serious fire hazard. Luckily, it’s pretty simple to diagnose the cause of the burning smell and enlist help from a pro to get your heater repaired if it’s something more urgent.

Is a Burning Smell From a Furnace Normal?

That funky smell is usually not typical, and you shouldn’t ignore it! If you notice the heater smells like burning for longer than a few hours, it may be a sign that your furnace needs maintenance, and it’s probably not something minor that will go away on its own.

Types of Heater Burning Smells and What They Mean

Finding the odor source can help you quickly understand if you’re facing a minor issue or need to hire a local HVAC contractor to make some repairs.

Burning Dust

When you turn your furnace off for extended periods (hello, summer), dust can collect on the heat exchanger and in the air ducts. When you turn the furnace back on, the dust burns off and releases an odor.

It’s normal for dust to burn off when the heater is turned on for the first time in the winter season and is generally not a cause for concern. This smell should disappear in a few hours, but you can also get rid of burnt smells in the home with these tips. If the problem persists, check your air filters.

Musty Odor

When you turn on your furnace for the first time each year, it may smell like a damp basement. The musty odor comes from dust and dirt collecting in the air ducts, which gets blown throughout your home when the furnace turns on. If this smell persists throughout the heating season, it could mean you need to change the air filter.

A musty smell could also indicate that mold is trapped on the furnace filter or the humidifier filter if you have one. Inspect the filter once a year and replace or clean it as needed. To clean a humidifier filter yourself, make a solution of water and vinegar in equal parts. Soak the filter in the solution and gently clean with a damp cloth.

Electrical Burning Smell

If you notice an odor that smells like burning plastic or burning electrical parts, it could be a foreign object in your HVAC system’s ductwork (like a child’s dropped toy or an unnoticed spill). When these items overheat, they can start to smell. Remove your registers and visually inspect them to clean or remove any objects that don’t belong.

It could also be something more serious, such as an overheated furnace motor or a cracked heat exchanger. If you cannot locate a foreign object in the ductwork, call an experienced technician to check the electrical components in the furnace.

Burning Oil or Smoke

If your furnace smells like smoke, it may indicate a blocked chimney, which could cause a dangerous flue fire. Or, if you operate an oil furnace and smell oil or smoke, it could mean a serious problem with your furnace. If the smell persists after checking and changing the oil filter, hire an HVAC technician to check it out.

How to Avoid the Heater Burning Smell and Future Furnace Trouble

Avoid more costly heater repairs in the future by having your furnace serviced and inspected at least once per year, ideally in the early fall before temperatures drop. A furnace inspection costs about $50 to $100, but will help your appliance last longer and protect your heater from needing more drastic (and expensive) repairs in the long run.

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