Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty

Musty furnace smells generally imply mold growth hiding in the HVAC system. To avoid subjecting your family to mold and mildew spores, address this problem right away.

A wet air filter can harbor mold, so eliminating the smell can be as simple as swapping out filter. If that doesn’t work, the AC evaporator coil fastened near the furnace could be the culprit. This component collects condensation, which could trigger mold growth. You’ll need a professional’s help to examine and clean the evaporator coil. When this still doesn't help, consider requesting air duct cleaning. This service cleans away hidden mold, no matter where it’s growing in your air ducts.

The Furnace Smells Like Rotting Eggs

This is one of the most worrisome furnace smells because it probably indicates a gas leak. The utility company includes a special substance known as mercaptan to the natural gas supply to make leaks easier to detect.

If you recognize a rotten egg smell around your furnace or originating from your vents, shut off the heater immediately. If you can find where the main gas supply valve is, shut that off too. Then, get out of the house and dial 911, followed by your gas company. Don’t reenter the house until a professional tells you 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 may mean the heat exchanger is cracked. This vital component houses combustion fumes, like carbon monoxide, so a crack could allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning could be lethal, so turn off your furnace right away if you notice a sour odor. Then, call an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. 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 fire up the furnace for the first time after a while, you probably expect a dusty odor to show up for a little while. This is the smell of six months’ worth of dust burning up as the furnace wakes up. As long as the smell disperses within one day, you shouldn'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 to the exterior. A smoky smell can 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 neglect it. So turn off the furnace and get in touch with a professional straightaway to schedule a repair.

The Furnace Smells Like It's Burning Plastic

Overheating and burned electrical components are the most likely 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 experience irreparable damage. Shut off the heating system right away and contact an HVAC technician for help troubleshooting and repairing this unusual furnace smell.

The Furnace Has an Oily Smell

If you have an oil furnace, you may notice this smell when the oil filter becomes blocked up. Try replacing it to determine if that resolves the problem. If the smell persists for more than one day after taking care of this step, it might imply an oil leak. You should get help from an HVAC specialist to address this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to rotten eggs, so first rule out the potential for a natural gas leak. If that’s not the source, your sewer lines might have an issue, such as a dry trap or sewer leak. Flush water down your own drains, including the basement floor drain, to refresh dried-out sewer traps. If the smell persists, go ahead and contact a sewer line repair company.

Contact Fras-Air/General Service Experts for Furnace Repair

If you're still unsure, get in touch with an HVAC technician to examine and repair your furnace. At Fras-Air/General Service Experts, we deliver complete diagnostic services to identify the problem before we figure out the best solution. Then, we suggest the most viable, cost-effective repairs, alongside an up-front estimate for each option. Our ACE-certified technicians can resolve just about any heating repair, and we back our work with a 100% satisfaction guarantee for one year. To learn more about why your furnace smells bad or to request furnace repair near you, please contact your local Fras-Air/General Service Experts office today.

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