Why Your Furnace Has a Strange Smell

As the weather gets colder and you switch from cooling to heating your home, some homeowners are worried about unusual furnace smells filling the air. Learn what the most common furnace smells could suggest and how concerned you should be about each one.

The Furnace Smells Musty

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

A clogged air filter can encourage mold, so eliminating the smell can be as straightforward as getting a new filter. If that fails to remove the smell, the AC evaporator coil placed near the furnace may be the root of the problem. This component gathers condensation, which could trigger mold growth. You’ll need a professional’s help to inspect and clean the evaporator coil. When this still doesn't help, consider scheduling air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your air ducts.

The Furnace Smells Like Spoiled Eggs

This is one of the most concerning furnace smells due to the fact that it probably suggests a gas leak. The utility company adds a particular substance called 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, shut off the heater immediately. If you remember where the main gas supply valve is placed, shut that off also. Then, leave the house and dial 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 notice a sour smell that stings your nose while standing near the furnace, this might mean the heat exchanger is cracked. This essential component houses combustion fumes, such as carbon monoxide, so cracks could pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be fatal, so shut off your furnace immediately if you notice a sour odor. Then, reach out to an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is to blame. For your continued safety going forward, see to it that you have reliable CO detectors on every floor of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time after a while, you probably expect a dusty odor to fill the house 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 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 could mean the flue is clogged, and now fumes are flowing back into your home. The odor can reach through the entire house, endangering your family’s health if you ignore it. So shut down the furnace and get in touch with a professional as soon as you can to request furnace 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 appear. A failing fan motor is another possibility. If you don’t address the problem, an electrical fire could start, or your furnace could end up with irreparable damage. Disable the heating system right away and call an HVAC technician for help identifying and repairing this unusual furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you may notice this smell when the oil filter becomes clogged. Try replacing it to determine if that resolves the problem. If the smell remains for more than 24 hours after taking care of this step, it may indicate an oil leak. You'll be better off with help from an HVAC expert to address this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to spoiled eggs, so first determine the likelihood of a natural gas leak. If that’s not the problem, the sewer lines might have an issue, such as a dry trap or sewer leak. Try pouring water down the drains, including the basement floor drain, to refresh dried-up sewer traps. If the smell sticks around, go ahead and contact a sewer line repair company.

Contact Atmostemp Service Experts for Furnace Repair

If you're still unsure, get in touch with an HVAC technician to check and repair your furnace. At Atmostemp Service Experts, we offer thorough diagnostic services to determine the problem before we figure out the best solution. Then, we suggest the most viable, cost-effective repairs, along with 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 ask questions about why your furnace smells bad or to request furnace repair near you, please contact your local Atmostemp Service Experts office today.

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