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 almost always suggest mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, handle this problem as soon as possible. 

A damp air filter can harbor mold, so wiping out the smell might be as easy as replacing the filter. If that doesn’t work, the AC evaporator coil mounted near the furnace could be to blame. This component gathers condensation, which could trigger mold growth. You’ll be better off with a professional’s help to inspect and clean the evaporator coil. When all else fails, consider requesting air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your air ducts. 

The Furnace Smells Like Rotten Eggs 

This is one of the most concerning furnace smells due to the fact that 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 easier to notice. 

If you notice a rotten egg smell near your furnace or coming from your vents, switch 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 dial 911, followed by your gas company. Don’t reenter 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 near64} the furnace, this could mean the heat exchanger has cracked. This vital component houses68} combustion fumes, such as carbon monoxide, so a crack 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 recognize 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 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 can 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 dissipates 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 could mean the flue is backed up, and now fumes are backdrafting into your home. The odor may permeate the entire house, endangering your family’s health if you let it continue. So shut down the furnace and get in touch with a professional right away to schedule a repair. 

The Furnace Smells Like Burning Plastic 

Overheating and melting electrical components are the most plausible reason for a burning plastic smell to come from your furnace. 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. Shut 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 could 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 suggest 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 eliminate 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 Knochelmann Service Experts for Furnace Repair 

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