Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty

Musty furnace smells usually suggest mold growth someplace in the HVAC system. To avoid subjecting your family to mold and mildew spores, address this problem as quickly as possible.

A clogged air filter can harbor mold, so eliminating the smell might be as easy as swapping out filter. If that doesn't help, the AC evaporator coil placed near the furnace might be the root of the problem. This component collects condensation, which could trigger mold growth. You'll want a professional’s help to examine and clean the evaporator coil. When the problem still won't go away, start thinking about investing in air duct cleaning. This service removes hidden mold, no matter where it's hiding in your ductwork.

The Furnace Smells Like Rotting Eggs

This is one of the most nerve-wracking furnace smells because it most likely implies a gas leak. The utility company puts in a particular substance known as mercaptan to the natural gas supply to make leaks easier to notice.

If you recognize a rotten egg smell around your furnace or originating from your air ducts, switch off the heater right away. If you remember where the main gas supply valve is placed, shut that off as well. Then, leave the house and call 911, followed by your gas company. Don’t reenter 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 may mean the heat exchanger cracked open. This essential component houses combustion fumes, such as carbon monoxide, so a crack may pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be lethal, so shut off your furnace immediately if you detect a sour odor. Then, call an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is the culprit. For your continued safety going forward, see to it that you have functional CO detectors on all floors of your home.

The Furnace Smells Dusty

When you start the furnace for the first time after a while, you probably expect a dusty odor to fill the house 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 a 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 will sometimes mean the flue is clogged, and now fumes are settling back into your home. The odor can reach through the entire house, jeopardizing your family’s health if you let it continue. So turn 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 plausible reason for a burning plastic smell to appear. A malfunctioning fan motor is another possibility. If you don’t tackle the problem, an electrical fire might start, or your furnace could experience irreparable damage. Turn off the heating system as soon as possible and call an HVAC technician for help diagnosing and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you may notice this stench 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 taking care of this step, it could indicate an oil leak. You should get help from an HVAC expert to address this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to spoiled eggs, so first rule out the possibility of a natural gas leak. If that’s not the problem, the 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 fill dried-up sewer traps. If the smell lingers, you should contact a sewer line repair company.

Contact Norrell Service Experts for Furnace Repair

If you're still uncertain, contact an HVAC technician to assess and repair your furnace. At Norrell Service Experts, we perform complete diagnostic services to pinpoint the problem before the work begins. Then, we recommend the most viable, cost-effective repairs, as well as 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 Norrell Service Experts office today.

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