Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty

Musty furnace smells generally indicate mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, address this problem as quickly as possible.

A wet air filter can lead to mold, so getting rid of the smell could be as straightforward as getting a new filter. If that fails to remove the smell, the AC evaporator coil placed near the furnace may be the culprit. This component collects condensation, which could trigger mold growth. You'll want a professional’s help to check and clean the evaporator coil. When the problem still won't go away, take a look at requesting air duct cleaning. This service removes hidden mold, no matter where it's hiding in your ventilation.

The Furnace Smells Like Rotten Eggs

This is one of the most concerning furnace smells since it frequently implies a gas leak. The utility company adds a useful substance known as mercaptan to the natural gas supply to make leaks easier to detect.

If you recognize a rotten egg smell near your furnace or out of your vents, shut down the heater right away. If you can find where the main gas supply valve is placed, shut that off also. Then, leave the house and contact 911, followed by your gas company. Don’t enter the house until a professional confirms it’s safe.

The Furnace Has a Sour Stench

If you discover a sour smell that stings your nose while standing near the furnace, this could mean the heat exchanger is cracked. This essential component houses combustion fumes, such as carbon monoxide, so cracks could spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be lethal, so shut off your furnace right away if you detect a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is the culprit. For your health and safety going forward, ensure you have working CO detectors on all floors of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time each fall, you probably expect a dusty odor to show up for a little while. This is the smell of six months’ worth of dust burning away as the furnace wakes from its summer slumber. 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 safely out of your home. A smoky smell could mean the flue is clogged, and now fumes are backdrafting into your home. The odor may permeate the entire house, endangering your family’s health if you ignore it. So switch off the furnace and call a professional right away to arrange for repair.

The Furnace Smells Like Burning Plastic

Overheating and melted electrical components are the most likely reason for a burning plastic smell to make an appearance. A failing fan motor is also possible. If you don’t tackle the problem, an electrical fire could start, or your furnace could experience irreparable damage. Turn off the heating system immediately and contact an HVAC technician for help troubleshooting and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you have an oil furnace, you could pick up on this stench whenever the oil filter becomes clogged. Try replacing it to see if that resolves the problem. If the smell lingers for more than 24 hours after carrying out this step, it might imply an oil leak. You should get help from an HVAC professional to address this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells very similar to rotting eggs, so first rule out the likelihood of a natural gas leak. If that’s not the source, your home's sewer lines might have an issue, such as a dry trap or sewer leak. Try pouring water down your own drains, including the basement floor drain, to fill dried-out sewer traps. If the smell persists, go ahead and contact a sewer line repair company.

Contact Stevenson Service Experts for Furnace Repair

If you're still unsure, call an HVAC technician to check and repair your furnace. At Stevenson Service Experts, we offer comprehensive diagnostic services to determine the problem before the work begins. Then, we recommend the most viable, cost-effective repairs, as well as an up-front estimate for all options. Our ACE-certified technicians can manage just about any heating malfunction, 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 Stevenson Service Experts office today.

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