Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, you may be worried about weird furnace smells filling the air. Learn about what the most common furnace smells could suggest and how concerned you should be about each one.

The Furnace Smells Musty

Musty furnace odors almost always indicate mold growth someplace in the HVAC system. To avoid exposing your family to allergy-inducing mold, handle this problem as soon as possible.

A wet air filter can encourage mold, so eliminating the smell can be as simple as replacing the filter. If that doesn't help, the AC evaporator coil placed near the furnace could be the root of the problem. This component gathers condensation, which will sometimes trigger mold growth. You'll be better off with a professional’s help to examine and clean the evaporator coil. When this still doesn't help, start thinking about requesting 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 worrisome furnace smells since it most likely suggests a gas leak. The utility company puts in a special substance known as mercaptan to the natural gas supply to make leaks easier to notice.

If you notice a rotten egg smell near your furnace or coming from your vents, shut off the heater straightaway. If you know where the main gas supply valve is located, shut that off too. Then, get out of the house and dial 911, followed by your gas company. Don’t go back in the house until a professional can verify it’s safe.

The Furnace Has a Sour Stench

If you notice a sour smell that stings your nose while standing near the furnace, this might mean the heat exchanger has cracked. This essential component contains combustion fumes, like carbon monoxide, so a cracked heat exchanger might pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning could be lethal, so shut off your furnace as soon as possible 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 to blame. For your continued safety going forward, ensure you have reliable CO detectors on every floor of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time every fall, you should expect a dusty odor to appear for a little while. This is the smell of six months’ worth of dust burning away as the furnace wakes up. As long as the smell goes away within a day, you have nothing to worry about.

The Furnace Has a Smoky Smell

Natural gas, oil and propane furnaces are combustion appliances, so they vent fumes safely out of your home. A smoky smell can mean the flue is blocked, and now fumes are flowing back into your home. The odor might eventually reach the entire house, jeopardizing your family’s health if you let it continue. So turn off the furnace and get in touch with a professional as soon as you can to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and melting electrical components are the most common reason for a burning plastic smell to come from your furnace. A malfunctioning fan motor is also possible. If you don’t tackle the problem, an electrical fire may start, or your furnace could suffer from irreparable damage. Disable the heating system immediately and call an HVAC technician for help troubleshooting and repairing this unpleasant furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you may notice this smell when the oil filter becomes blocked up. Try replacing it to find out if that resolves the problem. If the smell remains for more than a day after carrying out this step, it could imply an oil leak. You'll be better off with help from an HVAC specialist to handle this problem.

The Furnace Smell Resembles Sewer Odors

Sewer gas smells pretty similar to rotten eggs, so first eliminate the likelihood of a natural gas leak. If that’s not the issue, your home's sewer lines may have an issue, for example a dry trap or sewer leak. Flush water down the drains, including the basement floor drain, to fill dried-up sewer traps. If the smell lingers, you should contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

When in doubt, call an HVAC technician to check and repair your furnace. At Service Experts Heating & Air Conditioning, we perform comprehensive diagnostic services to identify the problem before we figure out the best solution. Then, we encourage the most viable, cost-effective repairs, alongside an up-front estimate for each option. Our ACE-certified technicians can resolve just about any heating problem, and we back our work with a 100% satisfaction guarantee for one year. For details about why your furnace smells bad or to request furnace repair near you, please contact your local Service Experts Heating & Air Conditioning office today.

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