Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty

Musty furnace smells almost always suggest mold growth somewhere in the HVAC system. To avoid subjecting your family to these microorganisms, address this problem as soon as possible.

A wet air filter can encourage mold, so eliminating the smell can be as straightforward as swapping out filter. If that fails to remove the smell, the AC evaporator coil placed near the furnace might be to blame. This component gathers condensation, which could trigger mold growth. You'll be better off with a professional’s help to inspect and clean the evaporator coil. When this still doesn't help, consider investing in air duct cleaning. This service eliminates hidden mold, regardless of where it’s growing in your air ducts.

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 includes a special substance called mercaptan to the natural gas supply to make leaks more easily detected.

If you notice a rotten egg smell close to your furnace or out of your air ducts, switch off the heater immediately. If you can find where the main gas supply valve is located, shut that off as well. Then, get out of the house and dial 911, in addition to your gas company. Don’t enter 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 close to the furnace, this could mean the heat exchanger is cracked. This important component safely contains combustion fumes, such as carbon monoxide, so a crack could allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be deadly, so switch off your furnace immediately if you recognize a sour odor. Then, reach out to an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. 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 brief moment. This is the smell of six months’ worth of dust burning off as the furnace wakes up. As long as the smell disperses within a 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 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 can reach through the entire house, jeopardizing your family’s health if you ignore it. So shut down the furnace and get in touch with a professional right away to schedule a repair.

The Furnace Smells Like It's Burning Plastic

Overheating and burned electrical components are the most common reason for a burning plastic smell to make an appearance. A malfunctioning fan motor is another common cause. If you don’t address the problem, an electrical fire may start, or your furnace could end up with irreparable damage. Turn off 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 have an oil furnace, you may detect this smell when the oil filter becomes blocked up. Try replacing it to see if that resolves the problem. If the smell remains for more than 24 hours after carrying out this step, it may imply an oil leak. You’ll need help from an HVAC specialist to fix this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells quite similar to spoiled eggs, so first determine the potential for a natural gas leak. If that’s not the problem, your home's sewer lines might have an issue, such as 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 persists, go ahead and contact a sewer line repair company.

Contact Aramendia Plumbing, Heating and Air for Furnace Repair

If you're still uncertain, call an HVAC technician to assess and repair your furnace. At Aramendia Plumbing, Heating and Air, we offer complete diagnostic services to determine the problem before repairs begin. Then, we suggest the most viable, cost-effective repairs, along with 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. To ask questions about why your furnace smells bad or to request furnace repair near you, please contact your local Aramendia Plumbing, Heating and Air office today.