Why Your Furnace Has a Strange Smell

As the weather turns cold and you swap from cooling to heating your home, you may be worried about unusual furnace smells in the air. Find out what the most common furnace smells mean and how worried you should be about them. 

The Furnace Smells Musty 

Musty furnace smells almost always suggest mold growth someplace in the HVAC system. To avoid subjecting your family to mold and mildew spores, tackle this problem as quickly as possible. 

A damp air filter can lead to mold, so wiping out the smell might be as simple as replacing the filter. If that doesn’t help, the AC evaporator coil placed near the furnace may be the root of the problem. This component gathers condensation, which can induce mold growth. You’ll want a professional’s help to examine and clean the evaporator coil. When all else fails, consider investing in air duct cleaning. This service removes hidden mold, regardless of where it’s growing in your ventilation. 

The Furnace Smells Like Spoiled Eggs 

This is one of the most nerve-wracking furnace smells since it frequently suggests a gas leak. The utility company adds a particular substance called mercaptan to the natural gas supply to make leaks more easily detected. 

If you recognize a rotten egg smell close to your furnace or out of your ductwork, switch off the heater straightaway. If you remember where the main gas supply valve is placed, shut that off as well. Then, leave the house and dial 911, followed by your gas company. Don’t enter the house until a professional confirms it’s safe. 

The Furnace Has a Sour Stench 

If you discover a sour smell that stings your nose while standing near64} the furnace, this might mean the heat exchanger cracked open. This vital component contains68} combustion fumes, such as carbon monoxide, so a crack may pump unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be lethal, so shut off your furnace immediately 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 responsible. For your health and safety going forward, ensure you have reliable CO detectors on all floors of your home. 

The Furnace Smells Dusty 

When you start the furnace for the first time every fall, you should expect a dusty odor to appear for a brief moment. This is the smell of six months’ worth of dust burning up as the furnace wakes from its summer slumber. As long as the smell disperses within 24 hours, 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 might eventually reach the entire house, endangering your family’s health if you let it continue. So switch off the furnace and call a professional as soon as you can to schedule a repair. 

The Furnace Smells Like Burning Plastic 

Overheating and melted electrical components are the most likely 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 may start, or your furnace could experience irreparable damage. Shut off the heating system immediately and contact 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 notice this stench when the oil filter becomes clogged. Try replacing it to determine if that resolves the problem. If the smell persists for more than 24 hours after carrying out this step, it may imply an oil leak. You’ll need help from an HVAC expert to address this problem. 

The Furnace Smell Resembles Sewer Odors 

Sewer gas smells pretty similar to rotten eggs, so first rule out the likelihood of a natural gas leak. If that’s not the source, your sewer lines might have an issue, such as a dry trap or sewer leak. Try pouring water down your own drains, including the basement floor drain, to replenish dried-out sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company. 

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

If you’re still uncertain, contact an HVAC technician to check and repair your furnace. At Service Experts Heating, Air Conditioning & Plumbing, we perform complete 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 each 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. To ask questions 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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