Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, some homeowners are worried about weird furnace smells filling the air. Find out what the most common furnace smells mean and how worried you should be about each one.

The Furnace Smells Musty

Musty furnace smells usually suggest mold growth hiding in the HVAC system. To avoid exposing your family to mold and mildew spores, handle this problem right away.

A clogged air filter can encourage mold, so wiping out the smell could be as straightforward as replacing the filter. If that doesn’t work, the AC evaporator coil placed near the furnace may be the culprit. This component gathers condensation, which will sometimes induce mold growth. You'll want a professional’s help to examine and clean the evaporator coil. When this still doesn't help, take a look at investing in air duct cleaning. This service cleans away hidden mold, regardless of where it’s growing in your ductwork.

The Furnace Smells Like Rotting Eggs

This is one of the most worrisome furnace smells due to the fact that it frequently implies a gas leak. The utility company puts in a special substance known as mercaptan to the natural gas supply to make leaks more easily detected.

If you recognize a rotten egg smell around your furnace or originating from your vents, shut down the heater right away. If you can find 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 enter the house until a professional can verify it’s safe.

The Furnace Has a Sour Stench

If you notice a sour smell that stings your nose while close to the furnace, this may mean the heat exchanger is cracked. This important component houses combustion fumes, like carbon monoxide, so cracks may spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be fatal, so switch off your furnace as soon as possible 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 the culprit. For your family's safety going forward, make sure you have functional 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 probably expect a dusty odor to show up for a little while. This is the smell of six months’ worth of dust burning off as the furnace wakes up. As long as the smell dissipates 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 could mean the flue is clogged, and now fumes are backdrafting into your home. The odor can reach through the entire house, jeopardizing your family’s health if you let it continue. So shut down the furnace and contact a professional as soon as you can to schedule a repair.

The Furnace Smells Like Burning Plastic

Overheating and melting electrical components are the most likely reason for a burning plastic smell to make an appearance. A malfunctioning fan motor is also possible. If you don’t correct the problem, an electrical fire could start, or your furnace could end up with irreparable damage. Disable the heating system immediately and call an HVAC technician for help troubleshooting and repairing this unpleasant furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you might detect this stench whenever the oil filter becomes clogged. Try replacing it to find out if that addresses the problem. If the smell remains for more than 24 hours after completing this step, it could suggest an oil leak. You'll be better off with help from an HVAC professional to address this problem.

The Furnace Smell Resembles Sewer Odors

Sewer gas smells quite similar to rotten eggs, so first eliminate the potential for a natural gas leak. If that’s not the source, your home's sewer lines might have an issue, for example a dry trap or sewer leak. Pour water down your own drains, including the basement floor drain, to refresh dried-out sewer traps. If the smell persists, go ahead and contact a sewer line repair company.

Contact Midway Services for Furnace Repair

When in doubt, contact an HVAC technician to examine and repair your furnace. At Midway Services, we deliver thorough diagnostic services to identify the problem before repairs begin. Then, we recommend the most viable, cost-effective repairs, alongside an up-front estimate for every 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 Midway Services office today.