Why Your Furnace Has a Strange Smell

As the weather cools down and you transition from cooling to heating your home, some homeowners are worried about unusual furnace smells filling the air. Find out what the most common furnace smells could mean and how proactive you should be about them.

The Furnace Smells Musty

Musty furnace odors almost always suggest mold growth someplace in the HVAC system. To avoid exposing your family to mold and mildew spores, address this problem as soon as possible.

A damp air filter can encourage mold, so eliminating the smell might be as easy as replacing the filter. If that fails to remove the smell, the AC evaporator coil mounted near the furnace might be to blame. This component accumulates condensation, which could induce mold growth. You’ll need a professional’s help to check and clean the evaporator coil. When this still doesn't help, start thinking about requesting air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your air ducts.

The Furnace Smells Like Spoiled Eggs

This is one of the most concerning furnace smells because it most likely indicates a gas leak. The utility company puts in a useful substance called mercaptan to the natural gas supply to make leaks easier to notice.

If you detect a rotten egg smell near your furnace or out of your vents, shut down the heater straightaway. If you know where the main gas supply valve is placed, shut that off too. Then, leave the house and call 911, as well as your gas company. Don’t go back in the house until a professional tells you 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 important component safely contains combustion fumes, such as carbon monoxide, so cracks might pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning could be fatal, so shut off your furnace immediately 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 the culprit. For your continued safety going forward, make sure you have functional CO detectors on every floor of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time after a while, you should expect a dusty odor to appear 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 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 blocked, and now fumes are flowing back into your home. The odor can reach through the entire house, endangering your family’s health if you neglect it. So shut down the furnace and call a professional right away to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and melting electrical components are the most plausible reason for a burning plastic smell to appear. A malfunctioning fan motor is another common cause. If you don’t address the problem, an electrical fire might 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 unpleasant furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you might pick up on this stench if the oil filter becomes blocked up. Try replacing it to determine if that fixes the problem. If the smell lingers for more than one day after taking care of this step, it could indicate an oil leak. You’ll need help from an HVAC professional to handle this problem.

The Furnace Smells Like Sewer Odors

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

Contact Freschi Service Experts for Furnace Repair

When in doubt, contact an HVAC technician to assess and repair your furnace. At Freschi Service Experts, we offer comprehensive diagnostic services to pinpoint the problem before the work begins. Then, we suggest the most viable, cost-effective repairs, alongside an up-front estimate for every option. Our ACE-certified technicians can manage just about any heating malfunction, 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 Freschi Service Experts office today.

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