Why Your Furnace Has a Strange Smell

As the weather gets colder and you transition from cooling to heating your home, you may be worried about strange furnace smells in the air. Learn what the most common furnace smells could mean and how proactive you should be about each one. 

The Furnace Smells Musty 

Musty furnace odors usually imply mold growth someplace in the HVAC system. To avoid exposing your family to mold and mildew spores, tackle this problem right away. 

A damp air filter can encourage mold, so eliminating the smell could be as simple as replacing the filter. If that doesn’t work, the AC evaporator coil fastened near the furnace could be to blame. This component gathers condensation, which could trigger mold growth. You’ll want a professional’s help to examine and clean the evaporator coil. When this still doesn’t help, start thinking about requesting air duct cleaning. This service cleans away hidden mold, regardless of where it’s growing in your air ducts. 

The Furnace Smells Like Spoiled Eggs 

This is one of the most worrisome furnace smells because it most likely implies 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 detect a rotten egg smell near your furnace or originating from your air ducts, shut off the heater immediately. If you know where the main gas supply valve is placed, 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 tells you 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 might mean the heat exchanger cracked open. This important component safely contains68} combustion fumes, like carbon monoxide, so a crack might allow unsafe levels of CO gas into your home. 

Carbon monoxide poisoning has the potential to be fatal, so shut off your furnace immediately if you notice a sour odor. Then, reach out to 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, see to it that you have working CO detectors on every floor of your home. 

The Furnace Smells Dusty 

When you fire up the furnace for the first time each 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 up. As long as the smell dissipates within 24 hours, you don’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 could mean the flue is blocked, and now fumes are flowing back 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 straightaway to arrange for repair. 

The Furnace Smells Like Burning Plastic 

Overheating and melted electrical components are the most plausible reason for a burning plastic smell to make an appearance. A failing fan motor is also possible. If you don’t address the problem, an electrical fire might start, or your furnace could suffer from irreparable damage. Turn off the heating system right away and call an HVAC technician for help diagnosing and repairing this unusual furnace smell. 

The Furnace Has an Oily Smell 

If you have an oil furnace, you might notice this stench when the oil filter becomes blocked up. Try replacing it to see if that resolves the problem. If the smell remains for more than a day after completing this step, it may imply an oil leak. You’ll need help from an HVAC professional to fix this problem. 

The Furnace Smell Resembles Sewer Odors 

Sewer gas smells quite similar to rotting eggs, so first rule out the potential for a natural gas leak. If that’s not the problem, your sewer lines might have an issue, for example a dry trap or sewer leak. Try pouring water down your own 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 

If you’re still uncertain, call an HVAC technician to assess and repair your furnace. At Service Experts Heating, Air Conditioning & Plumbing, we deliver comprehensive diagnostic services to determine the problem before the work begins. Then, we encourage the most viable, cost-effective repairs, as well as an up-front estimate for all options. 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 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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