Why Your Furnace Has a Strange Smell

As the weather cools down and you switch from cooling to heating your home, you might be worried about unusual furnace smells floating in the air. Find out what the most common furnace smells could mean and how concerned you should be about each one. 

The Furnace Smells Musty 

Musty furnace smells almost always indicate mold growth hiding in the HVAC system. To avoid exposing your family to these microorganisms, handle this problem as quickly as possible. 

A clogged air filter can harbor mold, so getting rid of the smell might be as easy as swapping out filter. If that doesn’t work, the AC evaporator coil mounted near the furnace might be to blame. 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 all else fails, start thinking about investing in air duct cleaning. This service cleans away hidden mold, no matter where it’s growing in your air ducts. 

The Furnace Smells Like Rotting Eggs 

This is one of the most concerning furnace smells because it probably indicates 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 notice a rotten egg smell near your furnace or out of your ductwork, shut off the heater right away. If you can find where the main gas supply valve is located, shut that off as well. Then, leave the house and dial 911, in addition to your gas company. Don’t go back in the house until a professional tells you it’s safe. 

The Furnace Has a Sour Stench 

If you detect a sour smell that stings your nose while standing close to64} the furnace, this could mean the heat exchanger has cracked. This important component contains68} combustion fumes, like carbon monoxide, so a crack could allow unsafe levels of CO gas into your home. 

Carbon monoxide poisoning has the potential to be deadly, so shut off your furnace immediately if you detect a sour odor. Then, contact 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, see to it that you have reliable 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 should expect a dusty odor to appear 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 disperses within one day, 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 to the exterior. A smoky smell can mean the flue is clogged, and now fumes are settling back into your home. The odor can reach through the entire house, jeopardizing your family’s health if you neglect it. So switch off the furnace and contact a professional right away to arrange for repair. 

The Furnace Smells Like Burning Plastic 

Overheating and melting electrical components are the most likely reason for a burning plastic smell to appear. A faulty fan motor is also possible. If you don’t address the problem, an electrical fire could start, or your furnace could experience irreparable damage. Turn off the heating system right away and contact an HVAC technician for help identifying and repairing this unusual furnace smell. 

The Furnace Has an Oily Smell 

If you have an oil furnace, you could detect this stench if the oil filter becomes blocked up. Try replacing it to determine if that resolves the problem. If the smell persists for more than one day after completing this step, it might imply an oil leak. You’ll be better off with help from an HVAC professional to fix this problem. 

The Furnace Smells Like Sewer Odors 

Sewer gas smells very similar to rotting eggs, so first determine the likelihood of a natural gas leak. If that’s not the problem, your sewer lines might have an issue, such as a dry trap or sewer leak. Flush water down your own drains, including the basement floor drain, to fill dried-out sewer traps. If the smell persists, you should contact a sewer line repair company. 

Contact Stevenson Service Experts for Furnace Repair 

When in doubt, get in touch with an HVAC technician to examine and repair your furnace. At Stevenson Service Experts, we deliver comprehensive diagnostic services to pinpoint the problem before repairs begin. Then, we suggest the most viable, cost-effective repairs, alongside an up-front estimate for every 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. For details about why your furnace smells bad or to request furnace repair near you, please contact your local Stevenson Service Experts office today. 

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