Why Your Furnace Has a Strange Smell

As the weather cools down and you switch from cooling to heating your home, you might be worried about weird 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 indicate mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, tackle this problem as soon as possible. 

A wet air filter can harbor mold, so eliminating the smell can be as simple as replacing the filter. If that doesn’t work, the AC evaporator coil placed near the furnace could be to blame. This component gathers condensation, which could stimulate mold growth. You’ll need a professional’s help to check 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 worrisome furnace smells since it most likely indicates a gas leak. The utility company adds a useful substance known as mercaptan to the natural gas supply to make leaks easier to notice. 

If you notice a rotten egg smell close to your furnace or coming from your vents, shut down the heater immediately. If you know where the main gas supply valve is located, shut that off also. Then, evacuate your home and call 911, followed by your gas company. Don’t reenter the house until a professional confirms it’s safe. 

The Furnace Has a Sour Stench 

If you detect a sour smell that stings your nose while standing close to64} the furnace, this could mean the heat exchanger has cracked. This vital component houses68} combustion fumes, like carbon monoxide, so a crack could pump unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be deadly, so shut off your furnace right away if you detect 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, 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 every fall, you should 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 blocked, and now fumes are settling back into your home. The odor may permeate the entire house, risking your family’s health if you neglect 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 make an appearance. A failing fan motor is another possibility. If you don’t tackle 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 troubleshooting and repairing this weird furnace smell. 

The Furnace Has an Oily Smell 

If you use an oil furnace, you might detect this odor if 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 completing this step, it could indicate an oil leak. You should get help from an HVAC expert to fix 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. Try pouring water down all your drains, including the basement floor drain, to refresh dried-out sewer traps. If the smell lingers, you should contact a sewer line repair company. 

Contact Strogen's Service Experts for Furnace Repair 

When in doubt, call an HVAC technician to assess and repair your furnace. At Strogen's Service Experts, we perform thorough 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 Strogen's Service Experts office today.