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5 Common Reasons Why Your Furnace Has a Funny Smell

5 Common Reasons Why Your Furnace Has a Funny Smell

If you smell something strange coming from your furnace, it could be trouble, or it could be nothing at all. Here are the most common smells and what you should do about them.

1. Musty Furnace Smells

When you turn on your furnace in the fall, you might notice that it smells. In most cases, this indicates that mold is growing in your ductwork or on the air conditioning coil located above your furnace. Unfortunately, you’ll need to hire a furnace professional for an inspection and cleaning. If there is no mold on the A/C coil, it is time to get your ducts cleaned since that is where the mold is forming.

2. Furnace Smells Like Rotten Eggs

Once again, it might mean nothing, but it might also mean you have a serious condition that requires immediate attention.

If you notice a rotten egg or sewer smell, then there’s a chance your furnace has a clogged oil burner or a clogged burner tube. If you’re not familiar with the term, a burner tube is the pipe that takes the gas from the burner to the gas valve and then to the main part of the furnace.

If the burner tube isn’t clear, the gas can’t travel to the valve, so that it will smell like rotten eggs or a sewer. If you smell that, it’s time to call in a furnace technician for an inspection. In some cases, the furnace may need to be replaced.

3. Burning Smell

If you notice a burning smell, then it may mean that the furnace is overheating. An overheating furnace can damage the motor, the blower, and the air conditioner. If you notice a burning smell, it’s time to shut the furnace off and call a furnace technician.

If you have to leave the house because of the burning smell, make sure you don’t leave an item on that needs to be turned off. For example, if you have a security system, make sure it’s turned off before you leave. If you don’t, you may come home to a burglar and a security system that’s going off. Also, make sure you turn off the carbon monoxide detector.

4. Dusty Smell

Don’t be alarmed if you start your furnace at the beginning of the heating season and smell dust. Throughout the summer, dust has accumulated on the interior of your furnace. The components that get heated, burn off the dust, and produce that noxious odor. It won’t be around for long.

5. Burning Plastic

If your furnace smells like burnt plastic or rubber, it might be due to an electrical fault. This burning smell can be given off by melting plastic wire casing, which is a safety issue. If you detect a melted plastic odor, switch off your heating system immediately and contact a specialist.


If your furnace smells, don’t just try to ignore the odor. If you ignore it, it could lead to bigger problems. To prevent spending more in the future, call a professional if you have an unusual odor coming from your furnace.

Don’t hesitate to contact us if you have any more questions about furnace repair and services. CG Heating and Cooling are here to help you!​ With over 20 years in business, we have the experience to handle all your heating and cooling needs.