Why Does My Furnace Smell Like Something Is Burning?

Published by Parisa Ostovari

It’s a common question that we get around this time of year, and it’s the reason that you’re reading this right now: Why is there a burning smell when I turn on 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.


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.

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.


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.

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 professional. We’ll inspect your unit for other possible sources of the odor.


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.

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

How to Avoid Strange Furnace Smells

Maintenance is key in avoiding a troublesome furnace smell. 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.

Give us a call at 515-244-8911 or contact us online to schedule your HVAC maintenance appointment.