Why Your Furnace Has a Strange Smell

As the weather cools down and you swap from cooling to heating your home, you might be worried about unusual furnace smells floating in the air. Learn about what the most common furnace smells could suggest and how worried you should be about them.

The Furnace Smells Musty

Musty furnace odors almost always imply mold growth someplace in the HVAC system. To avoid subjecting your family to these microorganisms, handle this problem as soon as possible.

A wet air filter can harbor mold, so eliminating the smell might be as simple as swapping out filter. If that fails to remove the smell, the AC evaporator coil mounted near the furnace could be to blame. This component accumulates condensation, which could stimulate mold growth. You’ll need a professional’s help to examine and clean the evaporator coil. When the problem still won't go away, take a look at scheduling air duct cleaning. This service cleans away hidden mold, no matter where it’s growing in your ductwork.

The Furnace Smells Like Rotten Eggs

This is one of the most worrisome furnace smells because it frequently suggests a gas leak. The utility company includes a special substance known as mercaptan to the natural gas supply to make leaks easier to detect.

If you recognize a rotten egg smell close to your furnace or originating from your vents, shut off the heater immediately. If you can find where the main gas supply valve is located, shut that off as well. Then, leave the house and call 911, as well as your gas company. Don’t enter the house until a professional can verify it’s safe.

The Furnace Has a Sour Stench

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

Carbon monoxide poisoning can be deadly, so turn off your furnace right away if you recognize a sour odor. Then, call an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is the culprit. For your family's safety going forward, see to it that you have reliable CO detectors on each floor of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time each fall, you probably expect a dusty odor to fill the house for a few minutes. This is the smell of six months’ worth of dust burning off as the furnace wakes up. As long as the smell goes away 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 up and out of your home. A smoky smell could mean the flue is blocked, and now fumes are backdrafting into your home. The odor may permeate the entire house, risking your family’s health if you neglect it. So shut down the furnace and call a professional as soon as you can to request furnace repair.

The Furnace Smells Like Burning Plastic

Overheating and burned electrical components are the most likely reason for a burning plastic smell to make an appearance. A faulty fan motor is another common cause. If you don’t tackle the problem, an electrical fire could start, or your furnace could end up with irreparable damage. Turn off the heating system right away and contact an HVAC technician for help troubleshooting and repairing this unusual furnace smell.

The Furnace Has an Oily Smell

If you use an oil furnace, you could notice this smell when the oil filter becomes blocked up. Try replacing it to see if that fixes the problem. If the smell remains for more than one day after taking care of this step, it may imply an oil leak. You’ll need help from an HVAC professional to handle this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells quite similar to rotting eggs, so first eliminate the potential for a natural gas leak. If that’s not the source, your sewer lines could have an issue, such as a dry trap or sewer leak. Try pouring water down all your drains, including the basement floor drain, to replenish dry sewer traps. If the smell lingers, go ahead and contact a sewer line repair company.

Contact All American Air Service Experts for Furnace Repair

If you're still unsure, get in touch with an HVAC technician to assess and repair your furnace. At All American Air Service Experts, we deliver complete diagnostic services to determine the problem before the work begins. 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 All American Air Service Experts office today.

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