There’s A Smell Coming From My Heater

Why does my heater/heating unit smell when it’s on?

You should never ignore a foul smell when the heat turns on, it may be time to request maintenance from your local HVAC contractor. The severity of the issue is unknown until a technician is able to diagnose the problem. It may be a dirty filter, a broken electrical component, or clogged ducting.

Find the source of this issue as soon as possible to avoid costly repairs in the future.

Different furnace odors

When you turn on your furnace for the first time during winter, you may notice a smell. It may smell like a damp basement or like a collection of dirt or dust. This is because of the fact that dirt and dust can collect in the duct work. When you turn the furnace on, the debris gets blown throughout the house.

Leaving the furnace on for a long period of time causes dust to collect on the heat exchanger and in the duct work. This will burn off and release an odor once the furnace heats up. However, this is not a cause for concern. The smell should disappear withing a few hours.

Musty odors

If you notice a musty smell, mold could be trapped in the furnace filters. It could also be on the humidifier filter but not all furnaces have one. If they do,  inspect the filter once a year and replace if necessary.

Electrical burning smell

A spill or plastic in the duct work can cause a burning smell. Visually inspecting your registers and duct work can quickly give you an answer. However, if there isn’t anything in the duct work, a component of the heating system is responsible. A motor could be overheating, a cracked heat exchanger, or incorrect wiring.


If you are experiencing any smells coming from the vents, it’s highly recommended that you get a HVAC contractor to clean the air ducts. If it’s gotten to the point where people are noticing the odor, the air ducts are in bad shape and should be cleaned immediately before it puts someone’s health at risk.

View our page on “Duct Cleaning: Improving Your Home and Health


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