Why Your Furnace Has a Strange Smell

As the weather turns cold and you swap 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 them.

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 damp air filter can harbor mold, so wiping out the smell could be as straightforward as getting a new filter. If that fails to remove the smell, the AC evaporator coil fastened near the furnace may be to blame. This component collects condensation, which will sometimes induce mold growth. You’ll need a professional’s help to examine and clean the evaporator coil. When all else fails, start thinking about scheduling air duct cleaning. This service removes hidden mold, no matter where it’s growing in your ventilation.

The Furnace Smells Like Rotting Eggs

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

If you recognize a rotten egg smell around your furnace or out of your vents, shut down the heater immediately. If you remember where the main gas supply valve is located, shut that off also. Then, evacuate your home 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 detect a sour smell that stings your nose while standing close to the furnace, this might mean the heat exchanger has cracked. This essential component contains combustion fumes, such as carbon monoxide, so a crack might pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be deadly, so shut off your furnace as soon as possible if you detect a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is the culprit. For your continued safety going forward, see to it that you have working CO detectors on each floor of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time after a while, you can expect a dusty odor to appear for a few minutes. 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 24 hours, 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 safely out of your home. A smoky smell could mean the flue is backed up, and now fumes are flowing back into your home. The odor may permeate the entire house, endangering your family’s health if you ignore it. So shut down the furnace and contact a professional straightaway to arrange for repair.

The Furnace Smells Like Burning Plastic

Overheating and burned electrical components are the most common reason for a burning plastic smell to come from your furnace. A faulty fan motor is another possibility. If you don’t address the problem, an electrical fire may start, or your furnace could suffer from irreparable damage. Disable the heating system right away and call an HVAC technician for help identifying and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you might pick up on this stench when the oil filter becomes clogged. Try replacing it to find out if that addresses the problem. If the smell lingers for more than 24 hours after completing this step, it may suggest an oil leak. You'll be better off with help from an HVAC specialist to address this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to rotting eggs, so first eliminate the potential for a natural gas leak. If that’s not the issue, your sewer lines could have an issue, like a dry trap or sewer leak. Try pouring water down the drains, including the basement floor drain, to fill dried-up sewer traps. If the smell sticks around, go ahead and contact a sewer line repair company.

Contact Church Services for Furnace Repair

If you're still uncertain, call an HVAC technician to examine and repair your furnace. At Church Services, we deliver complete diagnostic services to identify 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 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 Church Services office today.