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A-1 Mechanical Blog

Why Does My Furnace Smell?


When you turn on the heat in your Grand Rapids area home, do you notice an odd odor wafting from your vents? If so, you’re probably wondering: “Why does my furnace smell?” A-1 Mechanical is here to help you decode furnace odors you may experience this heating season, including what each type of odor means and when these smells indicate possible troubles with your heating system.

Why Does My Furnace Smell?

When a funky odor comes out of your vents, try not to panic! Furnace odors are not always a cause for concern, and certain smells are completely normal. Decode the furnace odor you experience using our guide below – with this helpful information, you’ll know when to call us for help and when you can relax and let the odor pass.

Decoding Strange Furnace Smells

There are many different odors that cause homeowners to question why their furnace smells? Below, find the potential causes of common furnace odors that may pop up over the course of this year’s heating season.

Burning Smell

A burning smell from the furnace is quite common the very first time the furnace is used in the late fall.

Burning odors when you first start the furnace each year occur as the furnace burns off the fine layer of dust that has settled on internal system components, such as the burners or heat exchanger, over the off season. This odor can be more noticeable if you haven’t had your furnace professionally tuned up for the year, as cleaning is a part of this service. Usually, the odor should resolve after an hour or so if it is caused by the dust layer burning off – if the smell of burning persists, call us for furnace repair to diagnose the source of the odor.

Aside from burning dust, burning odors from a furnace can also be caused by overheated components inside the unit, including wiring or a motor that’s burning out. These burning odors can also smell metallic or similar to burning plastic, rubber, or oil.

Rotten Egg Smell

If you have a natural gas furnace, beware of the rotten egg smell inside your home. This odor indicates a possible gas leak somewhere in the system that is allowing the escaped natural gas to mix with the air supply and circulate into your home. Utility providers add an odorant to natural gas so that people can easily identify it in case of a leak, as natural gas naturally has no smell.

If you smell rotten eggs when using your furnace, shut off your furnace immediately, get all occupants out of the house, and call your gas utility provider to identify the source of the leak. If the furnace is determined to be the source of your natural gas leak, call us for furnace repair. Do not use the furnace again until it has been inspected, serviced, and cleared for use by a heating professional.

Chemical Smell

If you smell an odd yet sweet odor reminiscent of formaldehyde, it is possible that your furnace’s heat exchanger is cracked. A rattling noise noticed along with this odor is a strong indicator of this problem. A cracked heat exchanger can allow dangerous carbon monoxide to mix with heated air and enter your home, exposing your family.

When this smell occurs, evacuate the home immediately. Once everyone is in a safe location, call us to have your furnace repaired. Do not reenter the home until a professional alerts you that it is safe to do so.

Furnace Repairs in Grand Rapids, MI

Why does my furnace smell? Hopefully if you notice furnace odors this winter, you’ll be able to easily decode them with our guide above. If you experience furnace odors that are a cause for concern as mentioned in this article or notice a smell not listed here, call A-1 Mechanical to request an appointment with an HVAC technician for furnace repair in your Grand Rapids area home.

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