Why Your Furnace Has a Strange Smell

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

The Furnace Smells Musty

Musty furnace smells usually indicate mold growth hiding in the HVAC system. To avoid exposing your family to allergy-inducing mold, address this problem as quickly as possible.

A clogged air filter can encourage mold, so wiping out the smell might be as simple as getting a new filter. If that fails to remove the smell, the AC evaporator coil placed near the furnace might be the culprit. This component accumulates condensation, which will sometimes stimulate mold growth. You’ll need a professional’s help to examine and clean the evaporator coil. When all else fails, consider investing in air duct cleaning. This service cleans away hidden mold, regardless of where it's hiding in your ductwork.

The Furnace Smells Like Rotting Eggs

This is one of the most concerning furnace smells due to the fact that it frequently indicates a gas leak. The utility company puts in a special substance called mercaptan to the natural gas supply to make leaks easier to notice.

If you recognize a rotten egg smell close to your furnace or originating from your air ducts, shut off the heater right away. If you know where the main gas supply valve is located, shut that off also. Then, evacuate your home and call 911, as well as your gas company. Don’t reenter the house until a professional tells you it’s safe.

The Furnace Has a Sour Stench

If you discover a sour smell that stings your nose while standing close to the furnace, this might mean the heat exchanger cracked open. This vital component contains combustion fumes, like carbon monoxide, so a crack may spew unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be fatal, so shut off your furnace as soon as possible if you notice 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, 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 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 disperses within a 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 to the exterior. A smoky smell will sometimes mean the flue is backed up, and now fumes are backdrafting into your home. The odor may permeate the entire house, risking your family’s health if you let it continue. So switch off the furnace and contact a professional straightaway to schedule a repair.

The Furnace Smells Like Burning Plastic

Overheating and burned electrical components are the most common 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 suffer from irreparable damage. Disable the heating system right away and call an HVAC technician for help diagnosing and repairing this unpleasant furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you might pick up on this stench whenever the oil filter becomes clogged. Try replacing it to determine if that resolves the problem. If the smell lingers for more than a day after completing this step, it could indicate an oil leak. You’ll need help from an HVAC expert to fix this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to rotten eggs, so first determine 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 the drains, including the basement floor drain, to fill dry sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

If you're still uncertain, contact an HVAC technician to assess and repair your furnace. At Service Experts Heating & Air Conditioning, we deliver thorough diagnostic services to pinpoint the problem before repairs begin. Then, we recommend the most viable, cost-effective repairs, as well as an up-front estimate for all options. 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 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.