Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, some homeowners are worried about unusual furnace smells filling 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 hiding 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 harbor mold, so eliminating the smell might be as simple as getting a new filter. If that doesn’t work, the AC evaporator coil placed near the furnace may be the culprit. This component gathers condensation, which could stimulate mold growth. You'll want a professional’s help to check and clean the evaporator coil. When the problem still won't go away, start thinking about investing in air duct cleaning. This service eliminates hidden mold, regardless of where it's hiding in your ductwork.

The Furnace Smells Like Spoiled Eggs

This is one of the most nerve-wracking furnace smells since it most likely indicates a gas leak. The utility company adds a special substance known as mercaptan to the natural gas supply to make leaks easier to notice.

If you recognize a rotten egg smell close to your furnace or out of your air ducts, switch off the heater immediately. If you can find where the main gas supply valve is located, shut that off too. Then, evacuate your home and contact 911, in addition to 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 close to the furnace, this may mean the heat exchanger cracked open. This vital component safely contains combustion fumes, like carbon monoxide, so cracks could spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be fatal, so shut off your furnace immediately if you recognize a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. 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 fire up the furnace for the first time after a while, you can expect a dusty odor to show up 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 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 safely out of your home. A smoky smell will sometimes mean the flue is clogged, and now fumes are flowing back into your home. The odor may permeate the entire house, endangering your family’s health if you let it continue. So turn off the furnace and get in touch with a professional right away to arrange for repair.

The Furnace Smells Like Burning Plastic

Overheating and burned electrical components are the most likely reason for a burning plastic smell to appear. A malfunctioning fan motor is another common cause. If you don’t tackle the problem, an electrical fire could start, or your furnace could suffer from irreparable damage. Shut off the heating system right away and contact an HVAC technician for help troubleshooting and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you use an oil furnace, you may notice this odor if the oil filter becomes blocked up. Try replacing it to see if that addresses the problem. If the smell remains for more than one day after taking care of this step, it might suggest an oil leak. You’ll need help from an HVAC professional to fix this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells very similar to rotting eggs, so first rule out the potential for a natural gas leak. If that’s not the problem, the sewer lines might have an issue, like a dry trap or sewer leak. Try pouring water down your own drains, including the basement floor drain, to replenish dried-up sewer traps. If the smell lingers, go ahead and contact a sewer line repair company.

Contact Sunbeam Service Experts for Furnace Repair

If you're still uncertain, call an HVAC technician to examine and repair your furnace. At Sunbeam Service Experts, we deliver comprehensive diagnostic services to identify the problem before the work begins. Then, we encourage the most viable, cost-effective repairs, as well as 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 Sunbeam Service Experts office today.

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