Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty 

Musty furnace odors usually imply mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, address this problem as soon as possible. 

A clogged air filter can harbor mold, so eliminating the smell can be as straightforward as replacing the filter. If that doesn’t work, the AC evaporator coil mounted near the furnace could be to blame. This component collects condensation, which will sometimes trigger mold growth. You’ll want a professional’s help to inspect and clean the evaporator coil. When all else fails, consider scheduling air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your ductwork. 

The Furnace Smells Like Rotten Eggs 

This is one of the most concerning furnace smells because it most likely suggests a gas leak. The utility company adds a useful substance known as mercaptan to the natural gas supply to make leaks more easily detected. 

If you notice a rotten egg smell around your furnace or coming from your vents, shut off the heater straightaway. If you know where the main gas supply valve is, shut that off also. Then, evacuate your home and dial 911, followed by your gas company. Don’t reenter 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 near64} the furnace, this could mean the heat exchanger cracked open. This vital component contains68} combustion fumes, including carbon monoxide, so a cracked heat exchanger could pump unsafe levels of CO gas into your home. 

Carbon monoxide poisoning could be lethal, so shut off your furnace right away if you detect 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 working CO detectors on every floor of your home. 

The Furnace Smells Dusty 

When you fire up the furnace for the first time every fall, you probably expect a dusty odor to fill the house 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 dissipates within a 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 may permeate the entire house, jeopardizing your family’s health if you ignore it. So turn off 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 common reason for a burning plastic smell to appear. A failing 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 immediately and call an HVAC technician for help diagnosing and repairing this weird furnace smell. 

The Furnace Has an Oily Smell 

If you use an oil furnace, you might detect this odor when the oil filter becomes clogged. Try replacing it to see if that fixes the problem. If the smell lingers for more than a day after carrying out this step, it could imply an oil leak. You’ll need help from an HVAC expert to address this problem. 

The Furnace Reeks of Sewer Odors 

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

Contact A-Plus for Furnace Repair 

When in doubt, contact an HVAC technician to examine and repair your furnace. At A-Plus, we deliver complete diagnostic services to pinpoint the problem before the work begins. Then, we recommend the most viable, cost-effective repairs, alongside an up-front estimate for all options. Our ACE-certified technicians can resolve 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 A-Plus office today.