Why Your Furnace Has a Strange Smell

As the weather turns cold and you transition from cooling to heating your home, you might be worried about weird furnace smells filling 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 almost always suggest mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, address this problem as soon as possible. 

A wet air filter can harbor mold, so eliminating the smell might be as straightforward 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 can induce mold growth. You’ll be better off with a professional’s help to inspect and clean the evaporator coil. When all else fails, consider requesting air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your ventilation. 

The Furnace Smells Like Rotten Eggs 

This is one of the most concerning furnace smells because it most likely implies a gas leak. The utility company includes a useful substance known as mercaptan to the natural gas supply to make leaks more easily detected. 

If you detect a rotten egg smell around your furnace or coming from your vents, shut off the heater immediately. 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 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 could mean the heat exchanger has cracked. This essential component houses68} combustion fumes, including carbon monoxide, so a crack 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 recognize a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is to blame. For your health and safety going forward, make sure you have functional CO detectors on each floor of your home. 

The Furnace Smells Dusty 

When you start the furnace for the first time every fall, you probably expect a dusty odor to fill the house for a little while. 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 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 settling back into your home. The odor may permeate the entire house, risking your family’s health if you let it continue. So shut down the furnace and call a professional right away to request furnace repair. 

The Furnace Smells Like Burning Plastic 

Overheating and melting electrical components are the most likely 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 identifying and repairing this weird furnace smell. 

The Furnace Has an Oily Smell 

If you have an oil furnace, you may notice this odor whenever the oil filter becomes clogged. Try replacing it to find out if that fixes the problem. If the smell lingers for more than a day after carrying out this step, it could suggest an oil leak. You’ll be better off with help from an HVAC expert to handle this problem. 

The Furnace Smell Resembles Sewer Odors 

Sewer gas smells quite similar to rotten eggs, so first eliminate 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 replenish dry sewer traps. If the smell lingers, you should contact a sewer line repair company. 

Contact BW/Cook Service Experts for Furnace Repair 

When in doubt, contact an HVAC technician to assess and repair your furnace. At BW/Cook Service Experts, we deliver complete 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 BW/Cook Service Experts office today.