Why Your Furnace Has a Strange Smell

As the weather cools down and you transition from cooling to heating your home, you might be worried about weird furnace smells in 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 odors usually suggest mold growth hiding in the HVAC system. To avoid exposing your family to these microorganisms, address this problem right away.

A clogged air filter can encourage mold, so getting rid of the smell might be as straightforward as getting a new filter. If that doesn’t work, the AC evaporator coil mounted near the furnace could be the root of the problem. This component gathers condensation, which can trigger mold growth. You'll want a professional’s help to examine and clean the evaporator coil. When the problem still won't go away, consider requesting air duct cleaning. This service removes hidden mold, no matter where it’s growing in your air ducts.

The Furnace Smells Like Rotten Eggs

This is one of the most nerve-wracking furnace smells since it frequently suggests a gas leak. The utility company includes a particular substance known as mercaptan to the natural gas supply to make leaks easier to detect.

If you notice a rotten egg smell around your furnace or originating from your ductwork, switch off the heater immediately. If you remember where the main gas supply valve is placed, shut that off as well. Then, evacuate your home and dial 911, as well as your gas company. Don’t enter the house until a professional confirms 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 could mean the heat exchanger cracked open. This essential component houses combustion fumes, such as carbon monoxide, so cracks might pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be fatal, so turn off your furnace right away if you recognize a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is the culprit. For your health and safety going forward, make sure you have reliable 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 probably expect a dusty odor to show up for a brief moment. This is the smell of six months’ worth of dust burning up as the furnace wakes up. As long as the smell goes away within 24 hours, 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 safely out of your home. A smoky smell could mean the flue is backed up, and now fumes are settling back into your home. The odor might eventually reach the entire house, endangering your family’s health if you ignore it. So switch off the furnace and contact a professional straightaway to arrange for repair.

The Furnace Smells Like It's Burning Plastic

Overheating and melting electrical components are the most plausible reason for a burning plastic smell to come from your furnace. A failing fan motor is also possible. If you don’t correct the problem, an electrical fire could start, or your furnace could end up with irreparable damage. Disable the heating system as soon as possible 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 might pick up on this stench if the oil filter becomes blocked up. Try replacing it to determine if that resolves the problem. If the smell lingers for more than a day after carrying out this step, it may suggest an oil leak. You'll be better off with help from an HVAC specialist to fix this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells quite similar to rotten eggs, so first determine the possibility of a natural gas leak. If that’s not the issue, the sewer lines may have an issue, such as a dry trap or sewer leak. Try pouring water down all your drains, including the basement floor drain, to fill dried-up sewer traps. If the smell lingers, go ahead and contact a sewer line repair company.

Contact Chief/Bauer Service Experts for Furnace Repair

If you're still unsure, get in touch with an HVAC technician to assess and repair your furnace. At Chief/Bauer Service Experts, we offer comprehensive diagnostic services to identify the problem before we figure out the best solution. 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 Chief/Bauer Service Experts office today.

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