Why does my furnace smell like it’s burning?

Does your house stink when the heater turns on? If your furnace smells, you shouldn’t ignore it.

Does your house stink when the heater turns on? If your furnace smells, you shouldn’t ignore it.

It’s that (cold) time of year again, and you’ve just turned on your heat for the first time this season… 

And you’re met with an odd burning smell coming from your furnace. What’s going on? And is it safe? Do you need a furnace replacement?

Burning smells are jarring and maybe even a little scary. But since the majority of homes use gas-run furnaces (60%), it’s actually a more common problem than you might think.

Here’s what you’ll cover in this guide:

It’s important to know, burning isn’t the only smell your furnace might give off.

It can smell like a lot of strange things, like rotten eggs, dust, or even melting plastic!

Luckily, each of those unique smells can be explained. 

So let’s dig into why your furnace smells like it’s burning (or any of the other odd stenches it can have).

We’ll even share the best way to keep your house from stinking like a smelly furnace.

Furnace smells like burning—or something else?

A burning smell coming from your furnace isn’t always a problem.

But often, it can be a sign of polluted indoor air. Some heating systems, especially those that run on fossil fuels, can cause toxic gasses to be drawn into your house. 

According to the EPA, poor indoor air quality can lead to lung diseases, heart diseases, cancer, and even pneumonia in children (2).

So strange smells aren’t just a health concern—and they’re a pretty important warning sign.

Depending on the type of smell coming from your furnace, you may be dealing with a potential fire hazard. Heating systems are a leading cause of home fires in the U.S. (3).  

So let’s find the source of your furnace’s smell (and why it stinks in the first place!). Here’s a quick list, and you’ll cover each below.

7 furnace smells you shouldn’t ignore:

  1. Gunpowder
  2. Burning oil and smoky aroma
  3. Burnt plastic
  4. Musty smell
  5. Rotten eggs
  6. Dust
  7. No smell (but carbon monoxide alarm is going off)

1. Gunpowder

Gunpowder smells from your furnace are more of an alarm for your system than a safety hazard for you. A gunpowder (or firework) scent typically means you’ve got a fried circuit board or an overheated fan motor.

Either one is a sign that you should turn off your furnace to avoid any further system issues and immediately call an HVAC technician to inspect the situation before turning it on again. 

2. Burning oil and smoky aroma 

Is it normal for a furnace to smell like burning? Well, sometimes. Oil furnaces tend to have an oily burning smell which is not necessarily an indication of a malfunction—as long as your air filters are up to date. If not, you’ll want to find a good HVAC pro to get to the bottom of your oily smoke smell. 

But take note: If your oil furnace smells like burning oil, even if that’s considered normal, those toxins are being released into your home—and you’re breathing them in.

3. Burnt plastic

 If you’re wondering why your furnace smells like burning plastic, here’s a few things to consider:

  • There’s a UFO in your system: These unidentified foreign objects could be kids’ or pets’ toys or even plastic utensils. 
  • Something’s overheating: Your furnace’s motor might be overheating. If this is the case, it’s time to turn it off and call an HVAC technician. 
  • Worn-out furnace parts: Plastic burning smells are sometimes a sign of a heater or electrical malfunction, which can cause the plastic electrical wire casing in your furnace to melt. They’re a signal that repairs are needed.

4. Musty smell

Does your furnace smell like it’s got B.O.? Believe it or not, a musty furnace isn’t always a red flag. Furnaces can give off a musty odor if they’ve been inactive for a while. 

They can also smell a bit rank upon startup for the heating season, but that fades over time. This is especially true if your heater and AC share the same air handler (your air handler is the way air travels throughout your house). 

Pro tip: Keeping your air filters clean and fresh can help prevent the dark, damp parts of your HVAC system from getting too musty over time.

And routine scheduled HVAC maintenance can make sure your heating and cooling systems are staying clean inside and out.

5. Rotten eggs

Not egg-actly the best smell around, but that’s actually a good thing.

This aggressive stench is a big warning, especially if you start to feel a bit drowsy each time you turn on your heater—you’re probably smelling sulfur from a oil or gas leak!

Oil and gas leaks are dangerous and require professional help. So if things are getting eggy, turn off your furnace ASAP.

6. Dust 

What does burning dust smell like, you ask? Well, mostly like something is burning, but you can’t quite tell what. Odds are, there’s a lot of dust gathered in and around your furnace after hibernating all summer.

When you turn it on, the dust burns, hence the burning, cooking-like smell—but it should go away in a few minutes. If it doesn’t, though, it might be time to call-in a heating system expert.

Fossil fuel home heating can give off carbon monoxide, so having detectors in your home is a must.

7. No smell (but carbon monoxide detector going off!)

Whodathunkit, the most alarming furnace smell can actually be… no smell at all!

Carbon monoxide poisoning in the home is a risk with fossil fuel heaters, like gas, propane, and oil furnaces. But carbon monoxide is odorless.

This is why it’s absolutely essential to have carbon monoxide detectors on every floor of your home.

So how do you know if your furnace is giving off carbon monoxide?

There are a few clues that you’ve got a carbon-monoxide leak: 

  • Soot around your furnace 
  • Other unusual smells that may be coming from the leak
  • Or—perhaps the most alarming—when your pilot light (a small gas flame) is yellow instead of blue. 

If you think you might have a carbon monoxide leak, turn off your HVAC system, evacuate your house, and call your local fire department and an HVAC technician—quick!

Carbon monoxide poisoning is nothing to mess with. 

No furnace smell should go unchecked

Did you know HVAC systems are supposed to get annual check-ups? It’s true. 

Experts recommend getting maintenance on your heating system in the fall (4). And that goes for newer or older systems, too, even if you think your HVAC works just fine. 

A typical maintenance check-up involves a technician coming to your home and inspecting:

  • Your thermostat
  • Your condensate drain and electrical connections
  • All moving parts and adding lubricants as needed 

Basically, this yearly checkup makes sure everything in your furnace is working okay—and safely. 

Hate having furnace smells in your home? Heat pumps solve the problem for good

Nearly half of the U.S. uses natural gas-run furnaces (5). 

That means almost half of the homeowners in this country could be heating their homes more efficiently and safely.

It also means many homeowners will deal with some sort of stench from their gas furnace this winter. 

But did you know there’s an alternative?

We’d like to introduce you to a little thing called a heat pump, aka the Tesla of HVAC.

Heat pumps are up to 3 times more efficient than traditional heating systems, like furnaces.

Heat pumps don’t produce heat by burning fuel to warm a house like most furnaces do.

heat pump vs. furnace in Chicago winter

Instead, they redistribute heat that’s present in the outside atmosphere into your home to warm it up.

(Yes, there’s still heat energy outside for heat pumps to work with even when it’s below zero. Read about how heat pumps work in winter here.)

heat pump outdoor compressor unit on green ivy wall: should you choose a geothermal or air source heat pump?

In the winter, heat pumps transfer heat from the outside and move it inside your home. And in the summer, they reverse the process by pulling indoor heat outdoors to keep your home cool. 

These sleek, versatile little powerhouses can reduce energy use for heating up to 50%, according to the Energy Department

And all types of heat pumps (also known as mini split ac or ductless heat pumps) run on clean, non-combustible energy that can drastically reduce your carbon footprint

Not to mention, you can also say goodbye to carbon monoxide risks in your home and annual burning dust smells. 

(Get the 411 on all things heat pumps with our ultimate guide.)

Heat pumps can reduce your heating energy use up to 50%.

Plus, heat pumps dehumidify and purify your home’s air while using as little as ⅓ the energy of traditional HVAC systems. With the right support from high-performance insulation and professional air sealing, they could cut your home’s energy waste in half!

Now if you feel like you’re in need of a breakup with your old, smelly furnace but don’t know how to pay for it, there’s a way out.

Give our article on how long HVAC systems last a read, and if it looks like your HVAC is on its last leg, it’s time to upgrade to an energy-efficient cold-climate heat pump!

Bonus? Heat pumps often qualify for financial incentives, like rebates from your utility company or homeowner tax credits under the Inflation Reduction Act.

And if your home qualifies to work with Sealed, you can get a new heat pump system installed for no upfront cost.

Call us at 917-382-3729 to learn more about upgrading to a heat pump—and finally say goodbye to odd furnace smells that mess with your indoor air quality.

Or complete our quick (and easy!) questionnaire to see if your home qualifies for a new heat pump with Sealed.

FAQs about why a furnace smells bad

Use the list below to jump ahead to the info you need for today:

Still have questions? Should you update your heating system? Give us a call at 917-382-3729. We love to talk home heating—especially with heat pumps!

Can a dirty air filter cause a burning smell?

Definitely! If a burning smell shows up every time you turn on your furnace, it might be your air filters. Dirty filters cause dust and grime build-up in your furnace that leads to a burning smell. 

Too much build-up overworks your system and could even cause it to shut down, so make sure your filters are fresh and clean. 

Do new furnaces smell?

Sometimes, your stinky furnace problem has a pretty simple reason: It’s new!

When a furnace is used for the first time, its protective oils coat the inside like a new oven, which releases a strange, burning sort of smell. It might last a day or two, but it’s nothing to worry about.

Can a furnace catch fire?

Furnaces can catch fire in certain instances. In fact, heating system fires are a leading cause of home fires in the U.S. (6). Make sure to have your furnace regularly inspected to make sure it’s in tip-top shape.

Can my furnace explode?

The short answer is yes, your furnace can explode. However, it’s not likely.

But if you want to avoid the fear altogether, heat pumps are a great and efficient alternative that can help cut your energy waste and filter your home’s air. They don’t burn fossil fuels in your home and have no risk of gas explosion.

What to do if your furnace smells like it’s burning?

A furnace that smells like it’s burning can be for a number of reasons. It could be that your furnace has been idle for a while and just needs to warm up, or it could be more serious reasons like a carbon monoxide or oil spill.

If you’re worried about your furnace’s smell, turn it off and reach out to an HVAC technician as soon as possible. 

furnace vs. heat pump

Finally, get rid of your stinky furnace for good

Tired of your old, worn-out, stinky furnace?

HVAC system upgrades can cost you upwards of five figures, upfront and out-of-pocket!

The good news? You’ve got other options. 

Heat pumps are the most efficient home heating system available. They use clean energy and are up to three times more energy-efficient than traditional HVAC, the faster we all get heat pumps installed, the faster we can cut down on our carbon footprint

But they aren’t just good for your home and the planet—they make your home feel amazing year round. (They’re an indoor air quality boost, too!)

Don’t let the cost stop you from optimizing your home to be more comfortable and efficient.

You can get your heat pump system installed for no upfront cost if your home qualifies… and say sayonara to burning furnace smells for good. 

Find out if you’re eligible for a new energy-efficient heat pump system at zero upfront cost.

October 21, 2022