Why Your Furnace Has a Strange Smell

As the weather turns cold and you transition from cooling to heating your home, some homeowners are worried about strange furnace smells floating in the air. Learn what the most common furnace smells could mean and how proactive you should be about each one.

The Furnace Smells Musty

Musty furnace odors almost always suggest mold growth hiding in the HVAC system. To avoid exposing your family to these microorganisms, address this problem right away.

A damp air filter can encourage mold, so wiping out the smell could be as easy as replacing the filter. If that doesn’t work, the AC evaporator coil mounted near the furnace could be the culprit. This component accumulates condensation, which could induce mold growth. You’ll need a professional’s help to check and clean the evaporator coil. When the problem still won't go away, start thinking about scheduling air duct cleaning. This service removes hidden mold, regardless of where it's hiding in your air ducts.

The Furnace Smells Like Spoiled Eggs

This is one of the most nerve-wracking furnace smells due to the fact that it probably suggests a gas leak. The utility company puts in a particular 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 vents, shut down the heater immediately. If you remember where the main gas supply valve is placed, shut that off as well. Then, get out of the house and dial 911, in addition to your gas company. Don’t enter 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 close to the furnace, this could mean the heat exchanger has cracked. This essential component contains combustion fumes, such as carbon monoxide, so cracks might allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning can be deadly, so shut off your furnace as soon as possible if you detect a sour odor. Then, contact an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is responsible. For your family's safety going forward, ensure you have working CO detectors on every floor of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time every fall, you should expect a dusty odor to fill the house 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 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 backed up, and now fumes are flowing back into your home. The odor can reach through the entire house, risking your family’s health if you ignore it. So turn off the furnace and call a professional as soon as you can to schedule a repair.

The Furnace Smell Resembles Burning Plastic

Overheating and melting electrical components are the most plausible reason for a burning plastic smell to appear. A malfunctioning 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. Turn off the heating system right away and call an HVAC technician for help diagnosing and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you own an oil furnace, you may detect this smell when the oil filter becomes clogged. Try replacing it to determine if that resolves the problem. If the smell remains for more than one day after carrying out this step, it might indicate an oil leak. You’ll need help from an HVAC specialist to fix this problem.

The Furnace Smells Like Sewer Odors

Sewer gas smells quite similar to spoiled eggs, so first eliminate the possibility of a natural gas leak. If that’s not the problem, the 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 refresh dried-out sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company.

Contact Knochelmann Service Experts for Furnace Repair

If you're still uncertain, call an HVAC technician to examine and repair your furnace. At Knochelmann Service Experts, we deliver complete diagnostic services to identify the problem before we figure out the best solution. Then, we suggest the most viable, cost-effective repairs, as well as 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. To ask questions about why your furnace smells bad or to request furnace repair near you, please contact your local Knochelmann Service Experts office today.

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