Why Your Furnace Has a Strange Smell

As the weather gets colder and you swap from cooling to heating your home, you may be worried about unusual furnace smells in the air. Learn about what the most common furnace smells could mean and how proactive you should be about each one. 

The Furnace Smells Musty 

Musty furnace odors almost always indicate mold growth somewhere in the HVAC system. To avoid exposing your family to mold and mildew spores, address this problem as quickly as possible. 

A wet air filter can harbor mold, so getting rid of the smell could be as straightforward as swapping out filter. If that doesn’t work, the AC evaporator coil placed near the furnace may be the culprit. This component accumulates condensation, which will sometimes trigger mold growth. You’ll be better off with a professional’s help to examine and clean the evaporator coil. When this still doesn’t help, take a look at scheduling air duct cleaning. This service cleans away hidden mold, regardless of where it’s hiding in your ductwork. 

The Furnace Smells Like Spoiled Eggs 

This is one of the most nerve-wracking furnace smells due to the fact that it most likely implies a gas leak. The utility company adds a special substance called mercaptan to the natural gas supply to make leaks more easily detected. 

If you notice a rotten egg smell around your furnace or originating from your air ducts, shut down the heater straightaway. If you know where the main gas supply valve is, shut that off too. Then, evacuate your home and call 911, as well as your gas company. Don’t enter the house until a professional confirms it’s safe. 

The Furnace Has a Sour Stench 

If you detect a sour smell that stings your nose while standing near64} the furnace, this could mean the heat exchanger has cracked. This essential component contains68} combustion fumes, including carbon monoxide, so a crack might allow unsafe levels of CO gas into your home. 

Carbon monoxide poisoning can be fatal, so turn off your furnace immediately 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 responsible. For your family’s safety going forward, make sure you have reliable CO detectors on each floor of your home. 

The Furnace Smells Dusty 

When you turn on the furnace for the first time each fall, you can expect a dusty odor to fill the house for a little while. This is the smell of six months’ worth of dust burning away as the furnace wakes up. As long as the smell goes away 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 clogged, and now fumes are flowing back into your home. The odor might eventually reach the entire house, jeopardizing your family’s health if you let it continue. So turn off the furnace and call a professional as soon as you can to schedule a repair. 

The Furnace Smell Resembles Burning Plastic 

Overheating and melted electrical components are the most likely reason for a burning plastic smell to make an appearance. A failing fan motor is another common cause. If you don’t address the problem, an electrical fire could start, or your furnace could experience irreparable damage. Disable the heating system right away and call an HVAC technician for help troubleshooting and repairing this unusual furnace smell. 

The Furnace Has an Oily Smell 

If you own an oil furnace, you might pick up on this smell when the oil filter becomes clogged. Try replacing it to determine if that addresses the problem. If the smell persists for more than one day after taking care of this step, it could suggest an oil leak. You’ll need help from an HVAC professional to address this problem. 

The Furnace Reeks of Sewer Odors 

Sewer gas smells very similar to rotten eggs, so first rule out the possibility of a natural gas leak. If that’s not the issue, your sewer lines could have an issue, for example a dry trap or sewer leak. Try pouring water down the drains, including the basement floor drain, to fill dry sewer traps. If the smell lingers, you should contact a sewer line repair company. 

Contact Service Experts Heating, Air Conditioning & Plumbing for Furnace Repair 

If you’re still unsure, contact an HVAC technician to assess and repair your furnace. At Service Experts Heating, Air Conditioning & Plumbing, we deliver thorough diagnostic services to pinpoint 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 manage just about any heating malfunction, 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 & Plumbing office today.