Why Your Furnace Has a Strange Smell

As the weather cools down and you swap from cooling to heating your home, you might be worried about weird furnace smells filling the air. Learn about what the most common furnace smells could suggest and how proactive you should be about each one.

The Furnace Smells Musty

Musty furnace smells generally imply mold growth somewhere in the HVAC system. To avoid exposing your family to these microorganisms, tackle this problem right away.

A wet air filter can encourage mold, so eliminating the smell can be as easy as replacing the filter. If that fails to remove the smell, the AC evaporator coil placed near the furnace may be to blame. This component collects condensation, which could stimulate mold growth. You’ll need a professional’s help to inspect and clean the evaporator coil. When all else fails, consider requesting air duct cleaning. This service cleans away hidden mold, no matter where it's hiding in your ventilation.

The Furnace Smells Like Rotting Eggs

This is one of the most concerning furnace smells due to the fact that it probably suggests 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 detect a rotten egg smell close to your furnace or out of your air ducts, shut down the heater immediately. If you know where the main gas supply valve is located, shut that off as well. Then, leave the house and contact 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 near the furnace, this might mean the heat exchanger cracked open. This essential component contains combustion fumes, like carbon monoxide, so cracks may spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be lethal, so switch off your furnace right away if you detect a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. For your continued safety going forward, ensure you have reliable CO detectors on all floors of your home.

The Furnace Smells Dusty

When you start the furnace for the first time each fall, you can expect a dusty odor to appear for a few minutes. This is the smell of six months’ worth of dust burning up as the furnace wakes up. As long as the smell dissipates within one 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 up and out of your home. A smoky smell will sometimes mean the flue is blocked, and now fumes are settling 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 call a professional straightaway to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and burned electrical components are the most plausible reason for a burning plastic smell to make an appearance. A failing fan motor is another possibility. If you don’t address the problem, an electrical fire might start, or your furnace could end up with irreparable damage. Shut off the heating system as soon as possible and contact 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 detect this odor if the oil filter becomes blocked up. Try replacing it to find out if that resolves the problem. If the smell remains for more than 24 hours after carrying out this step, it might indicate an oil leak. You'll be better off with help from an HVAC expert to handle this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells quite similar to rotten eggs, so first rule out the likelihood of a natural gas leak. If that’s not the issue, your home's sewer lines may have an issue, such as a dry trap or sewer leak. Try pouring water down your own drains, including the basement floor drain, to fill dry sewer traps. If the smell sticks around, you should contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

When in doubt, call an HVAC technician to check and repair your furnace. At Service Experts Heating & Air Conditioning, we deliver complete diagnostic services to determine the problem before the work begins. Then, we suggest the most viable, cost-effective repairs, as well as an up-front estimate for all options. 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 Service Experts Heating & Air Conditioning office today.