Why Your Furnace Has a Strange Smell

As the weather gets colder and you switch from cooling to heating your home, you might be worried about weird furnace smells floating in the air. Learn what the most common furnace smells mean and how concerned you should be about each one. 

The Furnace Smells Musty 

Musty furnace odors generally indicate mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, handle this problem as soon as possible. 

A damp air filter can harbor mold, so eliminating the smell might be as easy as replacing the filter. If that doesn’t work, the AC evaporator coil mounted near the furnace could be the root of the problem. This component collects condensation, which could stimulate mold growth. You’ll need a professional’s help to check and clean the evaporator coil. When all else fails, consider scheduling air duct cleaning. This service cleans away hidden mold, no matter where it’s growing in your air ducts. 

The Furnace Smells Like Rotten Eggs 

This is one of the most concerning furnace smells since it most likely indicates a gas leak. The utility company adds a useful substance known as mercaptan to the natural gas supply to make leaks easier to detect. 

If you detect a rotten egg smell around your furnace or coming from your vents, shut off the heater straightaway. If you know where the main gas supply valve is, shut that off too. Then, evacuate your home and dial 911, followed by your gas company. Don’t reenter 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 standing near64} the furnace, this could mean the heat exchanger cracked open. This vital component contains68} 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 lethal, so shut off your furnace right away 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 continued safety going forward, make sure you have reliable 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 should expect a dusty odor to appear for a little while. 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 dissipates within a 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 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, risking your family’s health if you neglect it. So turn off the furnace and contact a professional right away to arrange for repair. 

The Furnace Smell Resembles Burning Plastic 

Overheating and melting electrical components are the most common reason for a burning plastic smell to appear. A failing fan motor is another common cause. If you don’t address the problem, an electrical fire could start, or your furnace could experience irreparable damage. Turn off the heating system immediately and call an HVAC technician for help diagnosing and repairing this weird furnace smell. 

The Furnace Has an Oily Smell 

If you have an oil furnace, you may pick up on this odor if the oil filter becomes clogged. Try replacing it to see if that fixes the problem. If the smell lingers for more than a day after completing this step, it could indicate an oil leak. You’ll need help from an HVAC expert to fix this problem. 

The Furnace Reeks of 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 problem, your sewer lines could have an issue, such as a dry trap or sewer leak. Try pouring water down all your 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 Comfortech Service Experts for Furnace Repair 

When in doubt, contact an HVAC technician to assess and repair your furnace. At Comfortech Service Experts, we offer thorough diagnostic services to pinpoint the problem before the work begins. Then, we suggest the most viable, cost-effective repairs, as well as 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 Comfortech Service Experts office today.