Why Your Furnace Has a Strange Smell

As the weather turns cold and you transition from cooling to heating your home, some homeowners are worried about strange furnace smells in the air. Find out what the most common furnace smells could mean and how concerned you should be about each one.

The Furnace Smells Musty

Musty furnace smells usually imply mold growth somewhere in the HVAC system. To avoid subjecting your family to allergy-inducing mold, address this problem right away.

A wet air filter can harbor mold, so getting rid of the smell could be as easy as swapping out filter. If that doesn't help, the AC evaporator coil mounted near the furnace might be the root of the problem. This component collects condensation, which can stimulate mold growth. You’ll need a professional’s help to check and clean the evaporator coil. When all else fails, start thinking about investing in air duct cleaning. This service removes hidden mold, no matter where it’s growing in your ductwork.

The Furnace Smells Like Rotten Eggs

This is one of the most nerve-wracking furnace smells due to the fact that it most likely indicates a gas leak. The utility company adds a special substance called mercaptan to the natural gas supply to make leaks easier to notice.

If you detect a rotten egg smell near your furnace or originating from your vents, shut down the heater immediately. If you can find where the main gas supply valve is, shut that off too. Then, evacuate your home and contact 911, as well as your gas company. Don’t enter 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 to the furnace, this may mean the heat exchanger has cracked. This vital component houses combustion fumes, such as carbon monoxide, so a crack could pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be fatal, so switch off your furnace right away if you detect 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, make sure you have functional CO detectors on all floors of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time after a while, 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 away as the furnace wakes from its summer slumber. As long as the smell disperses 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 clogged, and now fumes are flowing back into your home. The odor can reach through the entire house, endangering your family’s health if you let it continue. So switch off the furnace and get in touch with a professional right away to schedule a repair.

The Furnace Smell Resembles Burning Plastic

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

The Furnace Has an Oily Smell

If you use an oil furnace, you may notice this stench if the oil filter becomes clogged. Try replacing it to find out if that fixes the problem. If the smell remains for more than one day after completing this step, it might imply an oil leak. You’ll need help from an HVAC specialist to handle this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells very similar to spoiled eggs, so first rule out the likelihood of a natural gas leak. If that’s not the problem, your sewer lines could have an issue, for example a dry trap or sewer leak. Flush water down the drains, including the basement floor drain, to replenish dried-out sewer traps. If the smell lingers, you’ll need to contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

When in doubt, call an HVAC technician to assess and repair your furnace. At Service Experts Heating & Air Conditioning, we deliver complete diagnostic services to determine the problem before we figure out the best solution. Then, we recommend the most viable, cost-effective repairs, as well as an up-front estimate for every option. Our ACE-certified technicians can handle just about any heating malfunction, 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 Service Experts Heating & Air Conditioning office today.