Why Your Furnace Has a Strange Smell

As the weather turns cold and you swap from cooling to heating your home, you might be worried about unusual furnace smells filling 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 indicate mold growth hiding in the HVAC system. To avoid subjecting your family to these microorganisms, handle this problem as soon as possible.

A wet air filter can lead to mold, so eliminating the smell can be as straightforward as swapping out filter. If that doesn’t work, the AC evaporator coil fastened near the furnace may be the root of the problem. This component accumulates condensation, which will sometimes stimulate mold growth. You'll be better off with a professional’s help to inspect and clean the evaporator coil. When all else fails, take a look at investing in air duct cleaning. This service removes hidden mold, regardless of where it’s growing in your air ducts.

The Furnace Smells Like Spoiled Eggs

This is one of the most nerve-wracking furnace smells because it most likely suggests a gas leak. The utility company includes a particular substance called mercaptan to the natural gas supply to make leaks easier to notice.

If you recognize a rotten egg smell near your furnace or out of your air ducts, shut down the heater straightaway. If you can find where the main gas supply valve is placed, shut that off as well. Then, evacuate your home and dial 911, in addition to your gas company. Don’t enter the house until a professional can verify it’s safe.

The Furnace Has a Sour Stench

If you discover a sour smell that stings your nose while standing near the furnace, this could mean the heat exchanger is cracked. This essential component houses combustion fumes, like carbon monoxide, so cracks could allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be lethal, so shut off your furnace immediately if you recognize a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is the culprit. For your health and safety going forward, see to it that you have functional CO detectors on each floor 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 up as the furnace wakes up. As long as the smell goes away within a 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 safely out of your home. A smoky smell could mean the flue is backed up, and now fumes are settling back into your home. The odor may permeate the entire house, endangering your family’s health if you neglect it. So switch off the furnace and contact a professional as soon as you can to schedule a repair.

The Furnace Smells Like Burning Plastic

Overheating and melted 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 tackle the problem, an electrical fire could start, or your furnace could suffer from irreparable damage. Disable the heating system right away 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 may detect this odor when the oil filter becomes blocked up. Try replacing it to find out if that resolves the problem. If the smell lingers for more than one day after completing this step, it could imply an oil leak. You’ll need help from an HVAC expert to fix this problem.

The Furnace Reeks of 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 home's sewer lines could have an issue, such as a dry trap or sewer leak. Flush water down the drains, including the basement floor drain, to refresh dried-up sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company.

Contact Midland Air Service Experts for Furnace Repair

If you're still uncertain, contact an HVAC technician to assess and repair your furnace. At Midland Air Service Experts, we deliver complete diagnostic services to determine the problem before repairs begin. Then, we suggest the most viable, cost-effective repairs, alongside an up-front estimate for all options. Our ACE-certified technicians can manage just about any heating repair, 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 Midland Air Service Experts office today.

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