Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty

Musty furnace smells generally indicate mold growth somewhere in the HVAC system. To avoid exposing 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 might be as straightforward as replacing the filter. If that doesn’t work, the AC evaporator coil mounted near the furnace might be the culprit. This component gathers condensation, which can induce 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 removes hidden mold, no matter where it's hiding in your ventilation.

The Furnace Smells Like Rotten Eggs

This is one of the most worrisome furnace smells because it frequently suggests a gas leak. The utility company adds a special substance called mercaptan to the natural gas supply to make leaks more easily detected.

If you recognize a rotten egg smell around your furnace or out of your ductwork, shut down the heater immediately. If you know where the main gas supply valve is placed, shut that off as well. Then, leave the house and contact 911, as well as your gas company. Don’t reenter the house until a professional can verify it’s safe.

The Furnace Has a Sour Stench

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

Carbon monoxide poisoning can be lethal, so switch off your furnace as soon as possible if you notice 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 reliable CO detectors on all floors of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time after a while, you can expect a dusty odor to fill the house 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 disperses within one 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 to the exterior. A smoky smell can mean the flue is backed up, and now fumes are flowing back into your home. The odor may permeate the entire house, jeopardizing your family’s health if you neglect it. So turn off the furnace and contact a professional as soon as you can 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 malfunctioning fan motor is also possible. If you don’t correct the problem, an electrical fire might start, or your furnace could suffer from irreparable damage. Turn off the heating system immediately and call an HVAC technician for help troubleshooting and repairing this unusual furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you may detect 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 24 hours after completing this step, it may indicate an oil leak. You’ll need help from an HVAC professional to fix this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells very similar to rotting eggs, so first determine the potential for a natural gas leak. If that’s not the issue, the sewer lines may have an issue, like a dry trap or sewer leak. Try pouring water down your own drains, including the basement floor drain, to fill dried-up sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company.

Contact Gordon's Service Experts for Furnace Repair

When in doubt, call an HVAC technician to check and repair your furnace. At Gordon's Service Experts, we perform thorough diagnostic services to determine the problem before the work begins. Then, we encourage the most viable, cost-effective repairs, along with an up-front estimate for each option. Our ACE-certified technicians can manage just about any heating repair, 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 Gordon's Service Experts office today.

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