Burning Smell from Furnace: Causes & How to Fix it

A burning smell coming from your furnace can be a big red flag. It’s not something you want to ignore. If left unchecked, it could lead to serious issues—think carbon monoxide leaks, potential fires, or expensive repairs down the road.

It’s always a good idea to make sure your furnace is in good working order before the start of winter, which can include a professional inspection and other key annual furnace maintenance steps.

Figuring out what’s behind the smell can save you a lot of trouble and keep your home safe and warm. It is better to catch it early than to deal with a disaster later.

In this article, we’ll cover the causes of that burning smell, how to fix it, and some precautions you can take to keep your furnace running safely.

Different Types of Furnace Smells and Their Causes

Let’s break down the different smells your furnace can give off and what they mean. Some smells are normal, while others need your attention right away.

1. Burning Plastic Smell from Furnace

If you’re getting a burning plastic smell from your furnace, that’s usually a sign of a broken or worn-out part. This could be things like:

• A faulty capacitor,
• Plastic-coated wires that may have caused an electrical fault
• Or even the fan belt wearing down.

It’s also possible that a toy or piece of plastic got into your ductwork and is melting from the heat.

How to Fix It?

First things first—turn off your furnace immediately. Keeping it running could damage the parts, lead to electrical issues, or even start a fire.

Once it’s off, remove the vent covers and look down into your supply ducts to see if anything is stuck. If you see a foreign object, grab a pair of tongs to reach in and pull it out carefully.

2. Burning Dust

Burning dust usually has a dry, earthy smell that’s mild and fades quickly—usually within an hour. The smell shouldn’t make your air quality noticeably worse.

It’s common when you first turn on your furnace for the season. On the other hand, a burning plastic smell is sharper and more chemical-like and doesn’t go away on its own.

Dust settles on the heat exchanger and other parts, and when the furnace is fired up, it burns off quickly.

How to Fix It?

Let the furnace run for about an hour if you notice a dusty smell. If the smell persists or gets worse, turn off the furnace and clean the air filters, vents, and area around the heat exchanger.

A quick vacuum or dust-off should do the trick. If the smell continues, it could indicate a deeper issue, and you might need to call a technician.

3. Smell of Burning Oil and Smoky Aroma

If you catch a whiff of burning oil or a smoky smell, that’s a big red flag. It might mean you have a leak, a malfunctioning burner, or improper combustion. This isn’t something to take lightly—leaking oil can be dangerous for both safety and the environment.

One common cause could be a blocked oil furnace filter. Remember, replacing that air filter every two to three months is key to keeping your furnace running smoothly.

How to Fix It?

Turn off your furnace immediately if you notice a burning oil smell. Check and replace the oil filter if it’s dirty or blocked.

If the smell persists or if you suspect a leak or combustion issue, call a professional HVAC technician right away. This is not a DIY fix, as oil leaks and burner issues can be hazardous if not handled properly.

4. Smell of Gunpowder

If your furnace smells like gunpowder or burning metal, it’s usually a sign of an overheated circuit board or fan motor. When these components overheat, they give off a unique, metallic scent, similar to gunpowder.

How to Fix It?

If you catch this smell, shut off your furnace immediately. Running it while overheating can cause serious damage or even lead to a fire. Don’t try to turn it back on until an HVAC professional has inspected the furnace and confirmed it’s safe.

5. Musty Smell

A musty smell coming from your furnace often points to moisture problems. It could be from standing water near the unit, excess humidity, or a failure to change the air filter regularly.

Mould growth is a common culprit, and sometimes, a furnace-burning smell comes with it. Minor musty odours may go away on their own, but if they linger, it’s worth checking for mould or mildew in and around your furnace.

How to Fix It

Turn off your heater, and give it a thorough cleaning. Replace the air filter to help improve airflow and reduce the chance of mold growth.

If the musty smell sticks around even after cleaning, the problem might be in your ductwork, where mold or mildew could be hiding.

6. Rotten Eggs

A rotten egg smell coming from your furnace is a big warning sign. It’s most likely a natural gas leak, which can be extremely dangerous, and could get your furnace red tagged. Even though natural gas is odorless, suppliers add a sulfur-like smell so leaks can be detected.

Prolonged exposure to leaking gas can lead to serious health issues like dizziness, nausea, or even suffocation. There’s also a risk of fire or explosion, so this is not something to ignore.

How to Fix It?

If you smell rotten eggs, leave your home immediately. Don’t use any electrical devices, flip switches, or light open flames, as any spark could trigger an explosion.

Once you’re safely outside, call your gas company to report the leak, and then contact an HVAC professional to inspect your furnace.

7. Scent of Burning Rubber from Your Furnace

If you catch a whiff of burning rubber, it usually means there’s an electrical problem. Burning rubber can release toxic fumes, so it’s not something you want to breathe in.

This smell can also indicate deteriorating furnace wiring, damaged insulation, or malfunctioning components.

Furnaces have safety mechanisms that should shut them down when they overheat, but if yours continues to run despite the smell, it might be a sign that something’s seriously wrong.

How to Fix It?

Shut off your furnace immediately to prevent further damage or exposure to toxic fumes. If possible, inspect the wiring and insulation, but don’t try to fix it yourself. Electrical issues can be complicated and dangerous.

Call an HVAC professional to diagnose the problem, repair damaged parts, and ensure your furnace is safe to use again.

8. Electrical Burning Smells

An electrical burning smell from your furnace is a serious issue that needs immediate attention. It can be caused by wear and tear, poor installation, or faulty wiring, leading to your heating system malfunctioning and overheating.

This could also be due to an overheated blower motor. Either way, it’s dangerous, and you should act quickly to prevent potential fire hazards.

How to Fix It?

Turn off your furnace as soon as you notice the smell. Don’t try troubleshooting electrical components yourself—it’s risky and complicated. Call an HVAC professional to inspect the system, check the wiring, and fix any damaged parts before turning it back on.

9. No Smell (but the carbon monoxide alarm is going off)

If your carbon monoxide alarm is sounding and there’s no noticeable smell, don’t ignore it. Carbon monoxide (CO) is colorless, odorless, and can be deadly. A leak could come from a malfunctioning furnace, poor ventilation, or a cracked heat exchanger, releasing CO into your home without any warning signs you can smell or see.

How to Fix It?

If your alarm goes off, get everyone out of the house immediately. Don’t open windows to “air out” the house—just leave. Once you’re safely outside, call your local fire department and your gas company.

Safety Precautions to Avoid Burning Smell from Furnace

Keeping your furnace in good shape helps you avoid strange and potentially dangerous smells and ensures your system runs efficiently. Here are some quick and easy tips to keep your furnace safe and odor-free:

• Replace Your Furnace Filter Every 90 Days: A clean filter helps your furnace work properly and prevents dust and debris from building up, reducing the chance of burning smells.
• Clean Before Use if It’s Been a While: If your furnace hasn’t been used in months, clean off dust and debris around the unit before turning it on for the first time.
• Schedule a Yearly Professional Inspection: Get your furnace checked by an HVAC technician once a year. They’ll inspect for worn-out parts, potential leaks, and overall performance to catch problems early. Old furnaces tend to produce more smoke than new ones..
• Keep Vents and Ducts Clear of Clutter: Don’t block or cover vents and duct openings with furniture, rugs, or other household items. Proper airflow reduces overheating and prevents foreign objects from entering the ducts.
• Check for Leaks Around the Unit Regularly: Take a quick look at your furnace and surrounding area occasionally. If you spot any signs of leaks, corrosion, or pooling water, get it checked by a professional immediately.
• Buy ENERGY STAR® Furnaces: Upgrading to an ENERGY STAR® certified furnace can help you save on energy costs and reduce the risk of burning smells. Gas furnaces with this certification use about 6% less energy, while oil-fueled models are about 9% more efficient.
• Consider a Hybrid Heating System: In Canada’s varying climate, combining a high-efficiency furnace with a heat pump maximizes comfort and saves energy. The heat pump handles milder weather, while the furnace takes over in colder temperatures, reducing strain on the system and lowering the risk of burning smells.

Frequently Asked Questions

Read More: 22 Common Furnace Problems with Troubleshooting Tips

Conclusion

A burning smell from your furnace can signal serious problems that need your attention immediately. Identifying the cause and taking action quickly can prevent more significant issues, such as gas leaks, electrical fires, or dangerous fume exposure.

If you’re dealing with any furnace issues or want peace of mind before the cold hits, we’re here to help. Work with the top 1% of HVAC companies and know that emergency service is available whenever needed.

Just answer a few quick questions—less than 30 seconds—and get your customized estimate. Don’t wait until a small problem turns into a major repair! Get a free quote today!