Why Your Furnace Has a Strange Smell

As the weather cools down and you swap from cooling to heating your home, some homeowners are worried about weird 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 usually imply mold growth hiding in the HVAC system. To avoid subjecting your family to mold and mildew spores, handle this problem as soon as possible.

A damp air filter can encourage mold, so wiping out the smell can be as easy as swapping out filter. If that doesn’t work, the AC evaporator coil placed near the furnace could be the root of the problem. This component collects 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 the problem still won't go away, consider investing in air duct cleaning. This service eliminates hidden mold, regardless of where it’s growing 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 frequently implies a gas leak. The utility company puts in a useful 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 ductwork, shut off the heater immediately. If you know where the main gas supply valve is located, shut that off as well. 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 notice a sour smell that stings your nose while close to the furnace, this may mean the heat exchanger cracked open. This essential component contains combustion fumes, such as carbon monoxide, so a cracked heat exchanger may allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning could be fatal, so switch off your furnace immediately if you notice 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 health and safety going forward, ensure you have working CO detectors on each floor of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time after a while, you probably expect a dusty odor to show up for a few minutes. This is the smell of six months’ worth of dust burning off as the furnace wakes from its summer slumber. As long as the smell goes away within a 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 can mean the flue is blocked, and now fumes are backdrafting into your home. The odor can reach through the entire house, risking your family’s health if you let it continue. So switch off the furnace and contact a professional right away to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and melted electrical components are the most plausible reason for a burning plastic smell to come from your furnace. A failing fan motor is another common cause. If you don’t address the problem, an electrical fire could start, or your furnace could suffer from irreparable damage. Shut off the heating system immediately and contact 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 could pick up on this stench if the oil filter becomes blocked up. Try replacing it to find out if that addresses the problem. If the smell persists for more than 24 hours after carrying out this step, it may suggest an oil leak. You'll be better off with help from an HVAC expert to address this problem.

The Furnace Smell Resembles Sewer Odors

Sewer gas smells quite similar to rotting eggs, so first rule out the likelihood of a natural gas leak. If that’s not the issue, your 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 replenish dry sewer traps. If the smell lingers, you should 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 assess and repair your furnace. At Service Experts Heating & Air Conditioning, we deliver complete diagnostic services to identify the problem before repairs begin. Then, we encourage the most viable, cost-effective repairs, alongside an up-front estimate for all options. Our ACE-certified technicians can handle 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 Service Experts Heating & Air Conditioning office today.