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 unusual furnace smells floating in the air. Learn what the most common furnace smells mean and how proactive you should be about each one.

The Furnace Smells Musty

Musty furnace odors almost always indicate mold growth someplace in the HVAC system. To avoid exposing your family to these microorganisms, tackle this problem as soon as possible.

A damp air filter can harbor mold, so getting rid of the smell can be as easy as replacing the filter. If that doesn’t work, the AC evaporator coil fastened near the furnace might be the root of the problem. This component gathers condensation, which can trigger mold growth. You'll be better off with a professional’s help to inspect and clean the evaporator coil. When the problem still won't go away, start thinking about scheduling air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your ventilation.

The Furnace Smells Like Rotting Eggs

This is one of the most concerning furnace smells because it frequently suggests a gas leak. The utility company includes a special substance known as mercaptan to the natural gas supply to make leaks easier to detect.

If you recognize a rotten egg smell near your furnace or originating from your vents, shut off the heater immediately. If you remember where the main gas supply valve is placed, shut that off too. Then, leave the house and contact 911, as well as 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 standing close to the furnace, this may mean the heat exchanger has cracked. This important component houses combustion fumes, including carbon monoxide, so a crack may spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be lethal, so turn off your furnace immediately if you detect 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 continued safety going forward, make sure you have working CO detectors on all floors of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time after a while, you should expect a dusty odor to appear for a few minutes. This is the smell of six months’ worth of dust burning away 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 can mean the flue is backed up, and now fumes are backdrafting into your home. The odor can reach through the entire house, endangering your family’s health if you let it continue. So switch off the furnace and get in touch with a professional straightaway to request furnace repair.

The Furnace Smells Like It's Burning Plastic

Overheating and burned electrical components are the most plausible reason for a burning plastic smell to make an appearance. A failing fan motor is another possibility. If you don’t correct the problem, an electrical fire may start, or your furnace could end up with irreparable damage. Turn off the heating system immediately and call an HVAC technician for help diagnosing and repairing this unusual furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you might detect this odor whenever the oil filter becomes clogged. Try replacing it to see if that addresses the problem. If the smell lingers for more than 24 hours after taking care of this step, it could imply an oil leak. You'll be better off with help from an HVAC specialist to handle this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells very similar to rotting eggs, so first determine the potential for a natural gas leak. If that’s not the issue, your sewer lines could have an issue, for example a dry trap or sewer leak. Try pouring water down the drains, including the basement floor drain, to fill dried-out sewer traps. If the smell sticks around, you should contact a sewer line repair company.

Contact McKinley Heating Service Experts for Furnace Repair

If you're still uncertain, get in touch with an HVAC technician to examine and repair your furnace. At McKinley Heating Service Experts, we perform thorough diagnostic services to determine 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 problem, 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 McKinley Heating Service Experts office today.

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