Homeowners may smell odors after turning their furnace on for the first time during fall or winter months.

Why Does My Furnace Smell When I Turn it On?

Posted: September 19, 2021 at 10:10 pm
By: Lakes Region HVAC

As we get hints of cooler weather here in New Hampshire, residents start thinking about turning their heat on. Many people notice an odor the first time they turn on their furnace for the heating season and wonder if this is cause for concern. Knowing what is common and what should be reason for concern is important for homeowners. In this blog we discuss some smells that might come from your furnace, what causes them and what, if any, action you should take.

Burning Dust

Dust burn-off is usually the cause of strange furnace smells when first turned on.

Furnaces commonly accumulate dust when they aren’t being used for months on end. This dust settles within the unit as well as on the heat exchanger and burners. When you turn on your heat this dust burns off and emits a smell throughout your home. It should dissipate quickly but if you notice it lingering for several hours or more than a day we recommend checking the air filter and replacing it if necessary, or have a local HVAC professional inspect the system.

Electrical Burning

If you notice an electrical burning, or metallic smell it could be from heat buildup in your furnace. Internal components of your furnace such as electrical wires or rubber pieces may be damaged, and the heat applied to the system can exacerbate the smell. In this case, shut the unit off immediately to prevent further damage or a fire, then contact an HVAC technician right away.

Burning or Melted Plastic Smell

If you notice a burning plastic smell coming from a specific register or vent, it could be a plastic toy or other foreign object in the duct. If it’s coming from your furnace, it could be an overheated motor, worn bearing or a wiring issue. Either way, if you smell this odor, it’s time to call a qualified HVAC technician and it is best to shut off your heating unit.

it’s best to contact your local HVAC professional if you are concerned about odors coming from your heating system.

Gunpowder Smell

Once the circuit board or fan motor overheats in a furnace, it will give off a smell that’s something similar to the smell of gunpowder. In this case, it is important to shut off your furnace immediately and have an HVAC professional visit your home to make necessary repairs. Don’t turn the furnace back on until the technician gives you the okay.

Rotten Egg or Sulfur Smell

If you smell rotten eggs or sulfur from any gas appliance in your home, it’s time to leave the premises and call the gas company immediately. Gas leaks are dangerous and should always be handled by trained professionals.

A reminder: annual furnace inspections can help you avoid issues when you decide to turn on your heat in the fall or winter. During a furnace tune-up and inspection your HVAC technician thoroughly cleans your unit (removing that dust accumulation!), changes furnace filters, and inspects and repairs parts that appear to need attention or replacement. This will make your furnace more efficient and save on repairs down the road.


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Have another question? Contact the Lakes Region team, and we’ll find your solution.

Our clients are homeowners, small business owners, and corporations—and one could be you by calling 603-286-2290 or emailing info@lrhvac.com.

About Lakes Region HVAC
Since 1992

Lakes Region’s expert service technicians and installers are trained in the latest advancements in heating and cooling technologies. We'll help you select the correct comfort system for your home, ensuring that your equipment operates at the highest efficiency — giving you the lowest monthly operating cost.

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LRHVAC’s office hours: Monday - Friday 7:30-4:30
Phone: (603) 286-2290
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