Why Your Furnace Has a Strange Smell

As the weather turns cold and you switch from cooling to heating your home, you might be worried about strange furnace smells floating in the air. Learn about what the most common furnace smells mean and how proactive you should be about each one.

The Furnace Smells Musty

Musty furnace smells usually imply mold growth hiding in the HVAC system. To avoid exposing your family to mold and mildew spores, address this problem as soon as possible.

A damp air filter can harbor mold, so eliminating the smell might be as simple as replacing the filter. If that fails to remove the smell, the AC evaporator coil mounted near the furnace may be the root of the problem. This component accumulates condensation, which will sometimes trigger mold growth. You'll be better off with a professional’s help to inspect and clean the evaporator coil. When the problem still won't go away, start thinking about requesting air duct cleaning. This service removes hidden mold, regardless of where it's hiding in your ductwork.

The Furnace Smells Like Rotting Eggs

This is one of the most worrisome furnace smells because it frequently implies a gas leak. The utility company adds a special substance called mercaptan to the natural gas supply to make leaks easier to detect.

If you detect a rotten egg smell near your furnace or originating from your vents, shut off the heater right away. If you can find where the main gas supply valve is, shut that off as well. Then, evacuate your home and call 911, in addition to 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 close to the furnace, this might mean the heat exchanger is cracked. This important component contains combustion fumes, such as carbon monoxide, so cracks could pump unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be lethal, so shut 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 to blame. For your family's safety going forward, ensure you have working CO detectors on all floors of your home.

The Furnace Smells Dusty

When you turn on the furnace for the first time every 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 disperses within one day, you don'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 clogged, and now fumes are settling back into your home. The odor might eventually reach the entire house, endangering your family’s health if you ignore it. So switch off the furnace and call a professional right away to schedule a repair.

The Furnace Smells Like It's Burning Plastic

Overheating and burned electrical components are the most likely reason for a burning plastic smell to come from your furnace. A faulty fan motor is also possible. If you don’t correct the problem, an electrical fire may start, or your furnace could experience irreparable damage. Turn off the heating system right away and call an HVAC technician for help diagnosing and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you use an oil furnace, you may pick up on this odor when the oil filter becomes clogged. Try replacing it to find out if that resolves the problem. If the smell persists for more than a day after carrying out this step, it could suggest an oil leak. You’ll need help from an HVAC expert to address this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells pretty similar to rotten eggs, so first rule out the possibility 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 all your drains, including the basement floor drain, to refresh dried-up sewer traps. If the smell persists, go ahead and contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

If you're still unsure, contact an HVAC technician to examine and repair your furnace. At Service Experts Heating & Air Conditioning, we perform thorough diagnostic services to identify the problem before we figure out the best solution. Then, we encourage the most viable, cost-effective repairs, as well as 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. To learn more about why your furnace smells bad or to request furnace repair near you, please contact your local Service Experts Heating & Air Conditioning office today.