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Furnace Smell Like Burning Plastic? | CroppMetcalfe

Oct 15, 2021

Why does my furnace smell like burning plastic?

Any time strange smells are coming from your furnace, it’s safe to assume there’s likely an issue present. Burning smells in particular mean your furnace requires a maintenance check since something is heating up in a way it shouldn’t. While the culprit might just be a dirty, forgotten filter, the worst-case scenario is some type of electrical failure or serious fire hazard. 


If you notice your furnace smells like burning plastic, don’t ignore it in the hopes that the smell goes away. Investigate to find the source of the odor and call in a professional HVAC technician if you can’t locate it right away. Quick action means catching the problem early which can prevent expensive repairs.

Why does my furnace smell like burning plastic?

If you notice that your furnace smells like burning plasticor perhaps burning rubber—then unfortunately you could be facing a serious internal problem with your unit. While there is a possibility that a small plastic object, such as a child’s toy, dropped into your ductwork, the smell of burning plastic coming from your furnace is indicative of an electrical issue.


4 possible answers to your question, “Why does my furnace smell like burning plastic?”:

1. A Lost Toy

If you know that the plastic smell is from a melting toy or spill in your ductwork, simply turn off your furnace and remove your registers. Thoroughly clean any areas of melted plastic and remove lost toys or any other objects that don’t belong. Replace the registers when the area is fully clean and your furnace should operate (and smell) like normal.

2. Electrical Issues

If you think the plastic smell could be an internal issue for your unit, understand that electrical issues can cause the plastic wire cases to melt. When an electrical issue occurs, your furnace may overheat, melting the wire casings, and giving off a burning rubber or plastic smell. In this case, it’s crucial that you stop using your furnace, turn it off, and call in an electrician to inspect the problem as quickly as possible.

3. Malfunctioning Heat Exchanger

Another reason why it’s possible that your furnace smells like burning plastic could be due to your unit’s heat exchanger breaking or overheating. When this part of your unit malfunctions, it can lead to your entire unit getting far hotter than it should. This can melt any plastic pieces in your furnace, even the wire casings. If your heat exchanger is broken, it will need to be repaired or replaced by a professional.

4. Dislodged Pieces

Lastly, some pieces of your furnace could come loose over time and through use. If any plastic pieces in your furnace are dislodged from their normal, safe-working location, they can end up melting and causing an unpleasant burning rubber smell. One example could be the humidifier nozzle breaking and falling towards your furnace’s heating elements. The nozzle can melt quickly. If this is the reason your furnace smells like burning plastic, contact your HVAC company to have the pieces replaced and the mess cleaned up.

Other Reasons Why Your Furnace May Smell Strange

Burning plastic smells aren’t the only smell to watch out for in your furnace. Whether the smells are happening by themselves or if they’re accompanied by strange sounds, unusual activity from your furnace needs to be investigated.


Here are 3 other smells to watch out for in your furnace and what they mean:

1. Furnace Smells Like Rotten Eggs

If you notice your furnace smells like rotten eggs, stop using your furnace at once, turn it off, and call your HVAC company and your gas company. The rotten egg smell can be an incredibly dangerous gas leak. Gas leaks can easily ignite, causing a massive explosion that could cause severe harm to the home and its occupants. Urgency is crucial.

2. Furnace Smells Like Smoke

A smoky smell coming from your furnace is likely serious. Stop using your furnace and call your HVAC company. If you have a home with a chimney, check to see if it’s blocked since that could cause smokey smells. Otherwise, the smell of smoke coming from your furnace indicates that it is overheating and burning something. It is a serious fire hazard.

3. Furnace Smells Like Burning Dust

Dust collects in your furnace, air ducts, and on all the different surfaces of your home constantly. This happens even when your unit is not operating, such as in the summer months. If you notice your furnace smells like burning dust the first time you turn it on for the cold season, there’s no reason for concern. Your heater is simply burning off the thin layer of dust that’s collected. 


If the smell persists for more than a few hours, however, then check your air filters to be sure they are clean and not contributing to the dust problem. If the problem persists, your unit could need a deep clean. Call your HVAC company for help with a furnace clean.

Keep Your Furnace Smelling Right

Any unusual smells coming from your furnace deserve investigation. Moldy, dirty, or burning smells all indicate something different—and possibly serious—with your HVAC unit. Don’t sit around hoping burning smells go away on their own. Schedule an appointment with CroppMetcalfe to get your furnace in proper working order and your home smelling right again.


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