Here's What To Do If Your Furnace Creates a Burning Smell

Closeup photo of family feet in woolen socks lying next to fireplace

Most homeowners are used to a burning smell coming from their furnace the first time they turn it on for the season, but what do you do when your heater smells like that all the time? While some furnace smells are completely normal, the smell of burning plastic, electrical odors, or burning dust may signal deeper issues with your HVAC system.

Find out what could be causing the smell of burning when you turn on your furnace by using this guide. Remember, here at Thomas & Galbraith Heating, Cooling & Plumbing, our team of NATE-certified professionals are always here to help.

How Should Normal Furnaces Smell?

During the year as your HVAC system is used, it may accumulate a fine layer of dust within the heat exchanger, ducts, and on the ignition system. When your furnace turns on for the very first time each season, you may smell a characteristic burning as dust within your system burns off. This smell may be unpleasant, but it shouldn’t last longer than an hour or significantly impact indoor air quality. If you are worried about the smell, you could crack a window slightly to air out your home until it goes away, or turn on a ventilation fan in a bathroom.

However, other scents can be warning signs. Natural gas is artificially scented to smell like rotten eggs, and if you smell it, there could be a leak in your system. Turn off your gas and call 911 or your utility provider. Mold and mildew can also signal issues within your furnace, as there may be moisture issues allowing mold to grow within your ductwork.

What Else Can Cause a Burning Smell?

While smelling a burning dust smell once a season isn’t necessarily a problem, burning odors that last could be a sign of a deeper issue. When something is physically burning inside your system, it could create an ongoing or intermittent burning smell that can recur throughout the winter.

Here are a few common causes of burning scents coming from the furnace:

Grimy Furnace Filter

Furnace filters are like a gateway for air to enter your system. As filters trap fine particulates like dust, pet dander, and airborne contaminants, your filter can become clogged. When filters fill up with debris, they can allow dust and grime to recirculate through your system, creating a bad odor. Additionally, when dust burns off within your system at the start of the season, the dirty filter will trap some of the odor molecules within your furnace, creating a lingering odor.

Air filters should be checked routinely and replaced whenever they become dirty. Keep extra air filters on hand for quick and simple replacement, and consider setting an alarm on your phone to check air filters every few weeks. Replacing air filters when they become dirty is essential preventative maintenance for your furnace and can help to extend its lifespan.

Overworked Blower Motor

Anytime your furnace filter is dirty or your ventilation lines contain clogs, your furnace is at a higher risk for overheating. Poor air movement can also be caused by blocked air return ducts, which can prevent cold air from circulating into the system. When this happens, heat can become trapped within the furnace, overheating components like your heat exchanger and blower motor. Furnaces that overheat may shut down, since the units contain internal limit switches that trip to protect the internal components. When furnaces overheat, the system can create a burning smell. Eventually, the system can accumulate so much heat repeatedly that the heat exchanger can crack, which can allow carbon monoxide to leak into your home.

If your furnace overheats, check the air filter and replace it if it looks dirty. Make sure all vents in your home are open and unobstructed, and that the thermostat is set to a reasonable heat setting. If filters are clean and your vents are in good, working order and open, it may be necessary to call an HVAC professional to troubleshoot your system.

Wires Burning

Burning plastic smells can signal a problem with electrical connections within your HVAC system. Anytime the insulation on a wire becomes damaged due to physical trauma, improper voltage, or incorrect placement, it can create a fault that burns off the protective insulation. When this happens, wiring can even spark a house fire. If you smell an electrical burning smell, take the issue seriously, and contact an HVAC technician for immediate diagnostics and repairs. Damaged wiring can be checked, replaced, or simply tightened. Electrical issues are a great reason to always have your furnace and HVAC equipment inspected and tuned-up at the start of the season.

Anytime You Need Heating Repair, Give Us A Call!

If your furnace stinks, give us a call here at Thomas & Galbraith Heating, Cooling & Plumbing. In addition to diagnosing the cause of bad odors coming from your furnace, our HVAC technicians can tune up your gas furnace and help you to keep your system in top condition. We are always available, so let us know if you are in need of furnace repair.

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