Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, you may be worried about strange furnace smells in the air. Find out what the most common furnace smells mean and how worried you should be about each one.

The Furnace Smells Musty

Musty furnace smells almost always indicate mold growth somewhere in the HVAC system. To avoid exposing your family to allergy-inducing mold, handle this problem as quickly as possible.

A damp air filter can lead to mold, so getting rid of the smell might be as straightforward as getting a new filter. If that fails to remove the smell, the AC evaporator coil fastened near the furnace could be to blame. This component accumulates condensation, which can induce mold growth. You’ll need a professional’s help to inspect and clean the evaporator coil. When this still doesn't help, take a look at investing in air duct cleaning. This service removes hidden mold, no matter where it’s growing in your ventilation.

The Furnace Smells Like Rotting Eggs

This is one of the most nerve-wracking furnace smells because it frequently indicates a gas leak. The utility company adds a particular substance known as mercaptan to the natural gas supply to make leaks more easily detected.

If you notice a rotten egg smell close to your furnace or out of your vents, shut off the heater immediately. If you know where the main gas supply valve is placed, shut that off as well. Then, get out of the house and dial 911, as well as 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 detect a sour smell that stings your nose while standing close to the furnace, this may mean the heat exchanger cracked open. This essential component safely contains combustion fumes, including carbon monoxide, so a crack might spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be deadly, so shut off your furnace immediately if you notice a sour odor. Then, call an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. For your family's 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 can expect a dusty odor to appear for a few minutes. 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 dissipates 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 will sometimes mean the flue is blocked, and now fumes are settling back into your home. The odor can reach through the entire house, endangering your family’s health if you neglect it. So shut down the furnace and get in touch with a professional right away to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and melting electrical components are the most likely reason for a burning plastic smell to come from your furnace. A malfunctioning fan motor is another common cause. If you don’t tackle the problem, an electrical fire may start, or your furnace could experience irreparable damage. Shut off the heating system as soon as possible and call an HVAC technician for help diagnosing and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you have an oil furnace, you might pick up on this smell if the oil filter becomes blocked up. Try replacing it to determine if that resolves the problem. If the smell persists for more than one day after completing this step, it may indicate an oil leak. You should get help from an HVAC professional to handle this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to rotten eggs, so first eliminate the likelihood of a natural gas leak. If that’s not the problem, your sewer lines might have an issue, for example a dry trap or sewer leak. Pour water down your own drains, including the basement floor drain, to fill dry sewer traps. If the smell sticks around, go ahead and contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

If you're still unsure, call an HVAC technician to examine and repair your furnace. At Service Experts Heating & Air Conditioning, we perform thorough diagnostic services to pinpoint the problem before the work begins. Then, we encourage the most viable, cost-effective repairs, along with an up-front estimate for all options. Our ACE-certified technicians can resolve just about any heating repair, and we back our work with a 100% satisfaction guarantee for one year. For details about why your furnace smells bad or to request furnace repair near you, please contact your local Service Experts Heating & Air Conditioning office today.

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