Why Your Furnace Has a Strange Smell

As the weather cools down 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 suggest and how worried you should be about each one.

The Furnace Smells Musty

Musty furnace smells usually suggest mold growth someplace in the HVAC system. To avoid exposing your family to these microorganisms, address this problem as soon as possible.

A clogged air filter can lead to mold, so wiping out the smell might be as easy as swapping out filter. If that doesn't help, the AC evaporator coil fastened near the furnace could be the culprit. This component collects condensation, which could trigger mold growth. You'll want a professional’s help to inspect and clean the evaporator coil. When all else fails, 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 Rotting Eggs

This is one of the most concerning furnace smells since it probably indicates a gas leak. The utility company adds a special substance called mercaptan to the natural gas supply to make leaks easier to notice.

If you recognize a rotten egg smell around your furnace or out of your vents, switch off the heater right away. If you can find where the main gas supply valve is, shut that off also. Then, get out of the house and contact 911, followed by your gas company. Don’t enter the house until a professional tells you it’s safe.

The Furnace Has a Sour Stench

If you detect a sour smell that stings your nose while standing close to the furnace, this may mean the heat exchanger cracked open. This important component contains combustion fumes, like carbon monoxide, so a crack might spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be lethal, so turn off your furnace as soon as possible 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 continued safety going forward, make sure you have functional CO detectors on each floor of your home.

The Furnace Smells Dusty

When you start the furnace for the first time each fall, 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 from its summer slumber. 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 backed up, and now fumes are settling back into your home. The odor can reach through the entire house, risking your family’s health if you neglect it. So switch off the furnace and call a professional as soon as you can to arrange for repair.

The Furnace Smells Like Burning Plastic

Overheating and burned electrical components are the most common reason for a burning plastic smell to come from your furnace. A failing fan motor is also possible. If you don’t tackle the problem, an electrical fire could start, or your furnace could end up with irreparable damage. Shut off the heating system as soon as possible and contact an HVAC technician for help identifying and repairing this unpleasant furnace smell.

The Furnace Has an Oily Smell

If you have an oil furnace, you could detect this odor if the oil filter becomes blocked up. Try replacing it to see if that addresses the problem. If the smell persists for more than 24 hours after completing this step, it may imply an oil leak. You'll be better off with help from an HVAC professional to fix this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells very similar to rotten eggs, so first rule out the possibility of a natural gas leak. If that’s not the issue, your home's 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 refresh dry sewer traps. If the smell persists, you’ll need to contact a sewer line repair company.

Contact D.A. Bennett Service Experts for Furnace Repair

If you're still unsure, get in touch with an HVAC technician to assess and repair your furnace. At D.A. Bennett Service Experts, we offer complete diagnostic services to identify the problem before we figure out the best solution. Then, we recommend the most viable, cost-effective repairs, as well as an up-front estimate for all options. Our ACE-certified technicians can handle just about any heating problem, 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 D.A. Bennett Service Experts office today.

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