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Help! My Furnace Smells Funny: What Should I Do?

furnace smells

There comes a moment in every homeowner’s life when the furnace cycles on and…what IS that smell?

There is a distinct aroma of—what is it, exactly—burning? Heat? Musty air?

Whatever it is, all you know is that it doesn’t smell right. It doesn’t smell safe.

But what should you do? Should you be concerned if you smell this odour only occasionally? What if your furnace has always smelled that way: Is that cause for worry?

We answer these and other timely questions about winter furnace odours in this post!

5 Commonly Reported Furnace Smells and What They Mean

This may not be what you want to hear, but furnaces can emit all kinds of strange smells.

The good news is, each odour typically functions as a type of handy early warning system—a heads-up if you will—to let you know to act now before the situation gets worse.

Let’s look at five commonly reported furnace smells and what they generally mean.

1. Burning or “smoky” smell

Both gas and oil-powered furnace types can emit an odour that homeowners describe as anything from “burning plastic” to “smoky” to flat-out burning. At any level, this is one of the scariest smells your furnace can kick out!

This type of odour can arise for a variety of reasons, one of the most common being incomplete combustion caused by improper maintenance or a new repair need.

Sometimes it can also arise because dust or debris has fallen into or accumulated on the furnace unit and it is being burned up.

2. Rotting eggs smell

The smell of rotting eggs is perhaps the least pleasant of all the different smells your furnace can produce, but it is often the easiest to diagnose.

Power companies usually add a rotten-smelling sulfur chemical to natural gas or propane gas for one reason: to act as a warning sign that you may have a gas leak. If you smell rotting eggs, this is your cue to power down and unplug all appliances that are using natural gas or propane gas until you can get a technician out to diagnose the problem.

You should also relocate yourself and your family, including your pets, to another place until the gas leak has been located and resolved. This is for your safety. Gas leaks can be fatal.  

3. Corn chips or “old cheese” smell

This is the scent given off when a concoction of bacteria and yeast microorganisms colonize an area and begin breeding. Yuck!

When you smell this odour coming from the vicinity of your heating system, chances are good that you have bacterial matter that has colonized in your heating coils. Seasonal shifts in humidity and temperature can be quite conducive to stealth bacteria that will move right in and take advantage of the warm, moist area around the heating coils to start new colonies.

The best way to resolve this particular odour is to schedule your heating system’s annual inspection and maintenance service, which includes a thorough cleaning that will remove the odour-producing bacteria.

4. Chlorine “pool” smell

If you like to swim in pools or your kids do, you have probably spent whole days breathing in the distinctive sharp scent of chlorine.

But would you believe your furnace can make a similar smell? Some owners describe this odour as more like a sharp, metallic scent, or even the smell of electrical circuits burning.

A poorly maintained, malfunctioning or worn-out heating system can make this smell if the blower motor becomes compromised. Your heater can start pulling more power trying to push the air through, in time throwing sparks sufficient to cause a home fire.

Power down your heating system and call a technician immediately if you notice this odour.

5. Musty, damp or “dirty socks” smell

Grassy, musty, mossy, damp, dirty gym socks, you name it—this smell is not for the faint of nose!

A musty, damp or faintly smoky odour can point to one of two issues: mould and mildew build-up around the heating system that is now burning away, or accumulated dust or debris that is burned off as the furnace heats up.

These types of odours are the least likely to present an urgent repair need—often the only time you will notice a scent like this is when you first power up your furnace for the winter.

However, if you notice similar odours after a few cycles have repeated, it may be a good idea to schedule your furnace inspection and maintenance service before running your heater further.

What Is Furnace Inspection and Maintenance Service?

Unless your furnace is getting up in years or you have recently inherited a poorly maintained heating system from a previous owner, typically you only need to schedule furnace inspection and maintenance once per year.

This service has two main purposes: to ensure your furnace system does not present a fire safety risk and to help improve your HVAC efficiency and lower your seasonal heating bills.

During your furnace inspection and maintenance appointment, your technician will thoroughly clean the exterior unit and the interior components, performing tune-ups, lubrication and minor repairs as needed and inspecting the power cables, connections and pilot light.

The service also includes a thermostat accuracy test and a cycle test to be sure your furnace is working properly.

Get in Touch

Does the air coming through your vents when the furnace is on smell strange? Or is your furnace showing other signs of perhaps needing a tune-up or a repair? Ask us about our popular year-round furnace protection plans!

Contact us online or give us a call at 905-549-4616.

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