Why Your Furnace Has a Strange Smell

As the weather turns cold and you swap from cooling to heating your home, you might be worried about weird furnace smells in the air. Learn what the most common furnace smells could mean and how proactive you should be about them.

The Furnace Smells Musty

Musty furnace smells usually indicate mold growth hiding in the HVAC system. To avoid subjecting your family to allergy-inducing mold, tackle this problem as soon as possible.

A clogged air filter can encourage mold, so eliminating the smell could be as easy as replacing the filter. If that fails to remove the smell, the AC evaporator coil fastened near the furnace may be the culprit. This component gathers condensation, which can stimulate mold growth. You’ll need a professional’s help to check and clean the evaporator coil. When all else fails, consider scheduling air duct cleaning. This service eliminates hidden mold, regardless of where it's hiding in your ductwork.

The Furnace Smells Like Spoiled Eggs

This is one of the most concerning furnace smells because it frequently suggests a gas leak. The utility company includes a useful substance known as mercaptan to the natural gas supply to make leaks more easily detected.

If you notice a rotten egg smell near your furnace or coming from your ductwork, shut off the heater straightaway. If you remember where the main gas supply valve is, shut that off too. Then, evacuate your home and dial 911, as well as your gas company. Don’t go back in the house until a professional confirms it’s safe.

The Furnace Has a Sour Stench

If you detect a sour smell that stings your nose while standing near the furnace, this may mean the heat exchanger cracked open. This important component houses combustion fumes, including carbon monoxide, so cracks could allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning could be lethal, so shut off your furnace right away if you detect a sour odor. Then, reach out to an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. For your family's safety going forward, see to it that you have functional CO detectors on all floors of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time each fall, you probably expect a dusty odor to fill the house for a few minutes. This is the smell of six months’ worth of dust burning away as the furnace wakes up. As long as the smell dissipates within one day, you don't have anything to worry about.

The Furnace Has a Smoky Smell

Natural gas, oil and propane furnaces are combustion appliances, so they vent fumes up and out of your home. A smoky smell will sometimes mean the flue is backed up, and now fumes are settling back into your home. The odor might eventually reach the entire house, risking your family’s health if you ignore it. So switch off the furnace and call a professional right away to request furnace repair.

The Furnace Smell Resembles Burning Plastic

Overheating and melted electrical components are the most common reason for a burning plastic smell to come from your furnace. A malfunctioning fan motor is another possibility. If you don’t address the problem, an electrical fire might start, or your furnace could end up with irreparable damage. Disable the heating system right away and contact an HVAC technician for help diagnosing and repairing this unusual furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you could notice this stench if the oil filter becomes clogged. Try replacing it to find out if that resolves the problem. If the smell remains for more than a day after completing this step, it could indicate an oil leak. You should get help from an HVAC expert to fix this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to spoiled eggs, so first determine the potential for a natural gas leak. If that’s not the issue, your sewer lines may have an issue, for example a dry trap or sewer leak. Pour water down your own drains, including the basement floor drain, to replenish dried-out sewer traps. If the smell persists, you’ll need to contact a sewer line repair company.

Contact Donelson Air Service Experts for Furnace Repair

When in doubt, contact an HVAC technician to check and repair your furnace. At Donelson Air Service Experts, we offer complete diagnostic services to identify the problem before the work begins. Then, we encourage the most viable, cost-effective repairs, along with an up-front estimate for all options. Our ACE-certified technicians can resolve just about any heating problem, and we back our work with a 100% satisfaction guarantee for one year. To ask questions about why your furnace smells bad or to request furnace repair near you, please contact your local Donelson Air Service Experts office today.

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