Why Your Furnace Has a Strange Smell

As the weather cools down and you transition from cooling to heating your home, you might be worried about weird furnace smells filling the air. Find out what the most common furnace smells could mean and how proactive you should be about them. 

The Furnace Smells Musty 

Musty furnace odors usually indicate mold growth somewhere in the HVAC system. To avoid exposing your family to mold and mildew spores, address this problem as quickly as possible. 

A wet air filter can harbor mold, so wiping out the smell might be as simple as swapping out filter. If that doesn’t help, the AC evaporator coil placed near the furnace may be to blame. This component collects condensation, which could trigger mold growth. You’ll be better off with a professional’s help to examine and clean the evaporator coil. When all else fails, consider requesting air duct cleaning. This service removes hidden mold, regardless of where it’s hiding in your ventilation. 

The Furnace Smells Like Spoiled Eggs 

This is one of the most concerning furnace smells since it frequently indicates a gas leak. The utility company puts in a useful substance called mercaptan to the natural gas supply to make leaks easier to notice. 

If you notice a rotten egg smell around your furnace or originating from your ductwork, shut 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 contact 911, in addition to your gas company. Don’t go back in 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 close to64} the furnace, this may mean the heat exchanger cracked open. This essential component houses68} combustion fumes, including carbon monoxide, so a cracked heat exchanger could pump unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be fatal, so turn off your furnace as soon as possible if you detect a sour odor. Then, call 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 functional CO detectors on every floor of your home. 

The Furnace Smells Dusty 

When you fire up the furnace for the first time after a while, you can expect a dusty odor to fill the house 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 goes away 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 safely out of your home. A smoky smell could mean the flue is clogged, and now fumes are backdrafting into your home. The odor might eventually reach the entire house, endangering your family’s health if you let it continue. So turn off the furnace and get in touch with a professional as soon as you can to request furnace repair. 

The Furnace Smells Like It’s Burning Plastic 

Overheating and burned electrical components are the most common reason for a burning plastic smell to appear. A faulty fan motor is also possible. If you don’t tackle the problem, an electrical fire might start, or your furnace could experience irreparable damage. Turn off the heating system immediately and call an HVAC technician for help identifying and repairing this unusual furnace smell. 

The Furnace Has an Oily Smell 

If you have an oil furnace, you might notice this odor whenever the oil filter becomes clogged. Try replacing it to find out if that resolves the problem. If the smell lingers for more than one day after taking care of this step, it might imply an oil leak. You’ll need help from an HVAC specialist to handle this problem. 

The Furnace Smell Resembles Sewer Odors 

Sewer gas smells quite similar to rotten eggs, so first determine the possibility of a natural gas leak. If that’s not the issue, your sewer lines could have an issue, like a dry trap or sewer leak. Try pouring water down your own drains, including the basement floor drain, to fill dry sewer traps. If the smell lingers, you’ll need to contact a sewer line repair company. 

Contact Service Experts Heating, Air Conditioning & Plumbing for Furnace Repair 

If you’re still unsure, contact an HVAC technician to assess and repair your furnace. At Service Experts Heating, Air Conditioning & Plumbing, we deliver comprehensive diagnostic services to identify the problem before the work begins. Then, we encourage the most viable, cost-effective repairs, along with an up-front estimate for each option. 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 Service Experts Heating, Air Conditioning & Plumbing office today. 

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