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 could mean and how concerned you should be about them. 

The Furnace Smells Musty 

Musty furnace odors almost always suggest mold growth someplace in the HVAC system. To avoid exposing your family to allergy-inducing mold, handle this problem as soon as possible. 

A wet air filter can lead to mold, so eliminating the smell could be as simple as swapping out filter. If that doesn’t work, the AC evaporator coil fastened near the furnace may be the root of the problem. This component accumulates condensation, which can stimulate mold growth. You’ll need a professional’s help to inspect and clean the evaporator coil. When the problem still won’t go away, consider requesting 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 because it probably indicates a gas leak. The utility company includes a special substance known as mercaptan to the natural gas supply to make leaks easier to notice. 

If you recognize a rotten egg smell near your furnace or originating from your vents, shut down the heater right away. If you remember where the main gas supply valve is placed, shut that off also. Then, get out of 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 discover a sour smell that stings your nose while standing close to64} the furnace, this could mean the heat exchanger is cracked. This vital component contains68} combustion fumes, including carbon monoxide, so a cracked heat exchanger could spew unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be fatal, so shut 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 to blame. For your family’s safety going forward, make sure you have functional CO detectors on every floor of your home. 

The Furnace Smells Dusty 

When you start 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 up as the furnace wakes from its summer slumber. As long as the smell goes away within one day, you shouldn’t have anything 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 can mean the flue is backed up, and now fumes are flowing back into your home. The odor might eventually reach the entire house, risking your family’s health if you ignore it. So switch off the furnace and contact a professional straightaway to request furnace repair. 

The Furnace Smells Like It’s Burning Plastic 

Overheating and melted electrical components are the most common reason for a burning plastic smell to appear. A faulty fan motor is another possibility. If you don’t tackle the problem, an electrical fire may start, or your furnace could experience irreparable damage. Disable the heating system as soon as possible and call an HVAC technician for help troubleshooting and repairing this unpleasant furnace smell. 

The Furnace Has an Oily Smell 

If you own an oil furnace, you may pick up on this stench if the oil filter becomes clogged. Try replacing it to see if that addresses the problem. If the smell persists for more than 24 hours after taking care of this step, it might imply an oil leak. You’ll be better off with help from an HVAC expert to handle this problem. 

The Furnace Smells Like Sewer Odors 

Sewer gas smells very similar to rotten eggs, so first determine the possibility of a natural gas leak. If that’s not the issue, your sewer lines may have an issue, like a dry trap or sewer leak. Flush water down all your drains, including the basement floor drain, to replenish dried-out sewer traps. If the smell lingers, go ahead and contact a sewer line repair company. 

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

If you’re still unsure, call an HVAC technician to check and repair your furnace. At Service Experts Heating, Air Conditioning & Plumbing, we offer thorough diagnostic services to determine the problem before the work begins. Then, we recommend the most viable, cost-effective repairs, along with an up-front estimate for all options. Our ACE-certified technicians can manage just about any heating malfunction, 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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