Why Your Furnace Has a Strange Smell

As the weather turns cold and you swap from cooling to heating your home, you might be worried about weird furnace smells filling the air. Learn about what the most common furnace smells mean and how concerned you should be about each one.

The Furnace Smells Musty

Musty furnace odors usually indicate mold growth hiding in the HVAC system. To avoid exposing your family to mold and mildew spores, address this problem as soon as possible.

A clogged air filter can lead to mold, so eliminating the smell might be as easy as getting a new filter. If that doesn't help, the AC evaporator coil placed near the furnace may be to blame. This component collects condensation, which can induce mold growth. You’ll need a professional’s help to inspect and clean the evaporator coil. When the problem still won't go away, take a look at requesting air duct cleaning. This service eliminates hidden mold, no matter where it's hiding in your ventilation.

The Furnace Smells Like Spoiled Eggs

This is one of the most worrisome furnace smells since it most likely implies a gas leak. The utility company puts in a special substance known as mercaptan to the natural gas supply to make leaks easier to detect.

If you notice a rotten egg smell close to your furnace or originating from your air ducts, shut off the heater immediately. If you know where the main gas supply valve is, shut that off too. Then, get out of the house and call 911, followed by your gas company. Don’t go back in 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 close to the furnace, this might mean the heat exchanger has cracked. This essential component contains combustion fumes, such as carbon monoxide, so a cracked heat exchanger may allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be lethal, so shut off your furnace right away if you notice a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is to blame. For your family's safety going forward, make sure you have functional CO detectors on all floors of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time each fall, you can expect a dusty odor to appear for a brief moment. This is the smell of six months’ worth of dust burning off as the furnace wakes from its summer slumber. As long as the smell goes away within 24 hours, you don'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 up and out of your home. A smoky smell could mean the flue is clogged, and now fumes are backdrafting into your home. The odor might eventually reach the entire house, risking your family’s health if you ignore it. So shut down the furnace and contact a professional as soon as you can to schedule a repair.

The Furnace Smells Like It's Burning Plastic

Overheating and burned electrical components are the most common reason for a burning plastic smell to make an appearance. A faulty fan motor is another common cause. If you don’t address the problem, an electrical fire could start, or your furnace could experience irreparable damage. Turn 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 might detect this stench whenever the oil filter becomes blocked up. Try replacing it to determine if that fixes the problem. If the smell remains for more than a day after completing this step, it might suggest an oil leak. You should get help from an HVAC expert to handle this problem.

The Furnace Smell Resembles Sewer Odors

Sewer gas smells very similar to spoiled eggs, so first eliminate the possibility of a natural gas leak. If that’s not the problem, your home's sewer lines could have an issue, like a dry trap or sewer leak. Flush water down all your drains, including the basement floor drain, to refresh dried-out sewer traps. If the smell sticks around, go ahead and contact a sewer line repair company.

Contact Strand Brothers Service Experts for Furnace Repair

When in doubt, call an HVAC technician to examine and repair your furnace. At Strand Brothers Service Experts, we deliver comprehensive diagnostic services to pinpoint the problem before repairs begin. Then, we suggest the most viable, cost-effective repairs, along with an up-front estimate for every 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 Strand Brothers Service Experts office today.

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