Why Your Furnace Has a Strange Smell

As the weather turns cold and you switch from cooling to heating your home, some homeowners are worried about unusual furnace smells filling the air. Learn what the most common furnace smells mean and how proactive you should be about them. 

The Furnace Smells Musty 

Musty furnace odors almost always imply mold growth somewhere in the HVAC system. To avoid exposing your family to mold and mildew spores, handle this problem right away. 

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

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 special substance called mercaptan to the natural gas supply to make leaks more easily detected. 

If you notice a rotten egg smell close to your furnace or out of your air ducts, shut down the heater right away. If you remember where the main gas supply valve is, shut that off also. Then, leave the house and call 911, as well as your gas company. Don’t go back in 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 may mean the heat exchanger has cracked. This important component safely contains68} combustion fumes, including carbon monoxide, so cracks could allow unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be deadly, so turn off your furnace as soon as possible if you notice a sour odor. Then, contact 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 reliable CO detectors on all floors of your home. 

The Furnace Smells Dusty 

When you start the furnace for the first time each fall, you should expect a dusty odor to fill the house 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 goes away 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 blocked, and now fumes are flowing back into your home. The odor may permeate the entire house, jeopardizing your family’s health if you neglect it. So switch off the furnace and call a professional straightaway 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 make an appearance. A faulty fan motor is also possible. If you don’t address the problem, an electrical fire may start, or your furnace could end up with 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 use an oil furnace, you could pick up on this stench if the oil filter becomes clogged. Try replacing it to find out if that resolves the problem. If the smell lingers for more than 24 hours after carrying out this step, it could suggest an oil leak. You should get help from an HVAC expert to handle this problem. 

The Furnace Smells Like Sewer Odors 

Sewer gas smells very similar to spoiled eggs, so first eliminate the potential for a natural gas leak. If that’s not the problem, your home’s sewer lines might have an issue, such as a dry trap or sewer leak. Try pouring water down the drains, including the basement floor drain, to refresh dried-out sewer traps. If the smell persists, you’ll need to contact a sewer line repair company. 

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

When in doubt, call an HVAC technician to examine and repair your furnace. At Service Experts Heating, Air Conditioning & Plumbing, we perform thorough diagnostic services to pinpoint the problem before repairs begin. Then, we encourage the most viable, cost-effective repairs, alongside an up-front estimate for all options. Our ACE-certified technicians can resolve just about any heating malfunction, and we back our work with a 100% satisfaction guarantee for one year. To learn more 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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