Why Does My Furnace Smell Like Something Is Burning?

It’s a common question we get around this time of year, and it’s the reason you’re reading this right now: Why is there a burning smell from my furnace?

First — don't panic. While a burning smell is unnerving, it doesn't necessarily mean there's an emergency. Let’s dive into three of the most common smells, what they mean and what you can do.

Dust

What you smell:

A light, dust-like burning scent.

What it means:

When a furnace is inactive for a while, dust and dirt particles can settle on and inside your furnace and ducts. As cooler weather rolls in and the heat kicks on for the first time in months, the dust burns off and releases a faint odor. This is one of the most common causes of a burning smell from a furnace when it starts up for the season.

What to do:

Wait. This is common and the smell should dissipate within an hour or so. If it doesn't, check your air filter — you may need to replace it. When an air filter gets dirty or clogged, the blower motor works harder and may overheat, causing a burning-like smell. If replacing your filter doesn't work, give your HVAC technician a call to inspect the system.

Musty

What you smell:

A moldy, musty, dirty sock-type scent.

What it means:

There are two likely causes. If this is the first time you’ve fired up the heat in months, it could be dust and dirt that’s accumulated in your ducts. A musty smell could also mean that your filter is dirty or even has mold. While not always described as a burning smell from the furnace, musty odors often get confused with overheating odors because they linger.

What to do:

If the smell doesn't go away within an hour or so, check and replace your filter. If the smell still lingers, call a furnace professional. We'll inspect your unit for other possible sources of the odor.

Plastic

What you smell:

Burning plastic or a crayon-like smell.

What it means:

There are a few possible causes. It could mean a foreign object got too close to the furnace or even ended up inside. Do you have small children? To them, air vents are like tunnels of mystery, and dropping toys or other objects inside the vents can be incredibly tempting — we've seen our fair share of surprises! A burning plastic smell could also indicate something more serious, like a scorched wire.

A burning plastic smell could also indicate something more serious, like a scorched wire. This type of burning smell from a furnace should never be ignored, as it may point to an electrical hazard.

What to do:

If your furnace smells like burning plastic, turn it off right away and call a professional.

Other Furnace Smells

The following furnace smells could indicate a serious issue and should be checked right away. If you detect any of the following scents, call a professional immediately:

• Electrical-type burning
• Foul or rotten eggs
• Metallic

These odors are often more dangerous than a standard burning smell from a furnace caused by dust and should be treated as emergencies.

Learn more: Winter Furnace Tune Up: How to Prepare Your Home for Cold Weather

How to Avoid Strange Furnace Smells

The best way to prevent a burning smell from your furnace is regular maintenance. First, replace your filter as often as it needs. How often depends on the kind you have, but most filters should be replaced at least once a month. Other filters, like high-efficiency filters, can last as long as six months.

Second, schedule annual maintenance with an HVAC professional. We’ll clean your unit, switch out your filter, and check the components to ensure your system stays up and running to keep your family comfortable all year long. Regular maintenance helps you avoid not just burning odors but also costly breakdowns and inefficient performance.

Contact us online to schedule your HVAC maintenance appointment.