Why does my furnace smell?

If you live in a climate with warm summers, you might go months at a time without having to use your furnace.

  • During this time, lots of things can happen to your furnace, and when you go to fire up your furnace on a cold day, it is possible for your furnace to make unusual smells.

While some smells can be an immediate cause for concern, other smells can go away on their own. Here are some smells you may experience from your furnace, and what you can do about them. It can be common to smell mold or mildew coming from your furnace after months of inactivity. Your ducts are cool, dark places where moisture can accumulate, and sometimes it can be agitated and smell like mildew. Typically the moisture in your vents will evaporate after several hours of running your furnace. If the smell persists after a few days, you should contact your HVAC provider to have your ducts cleaned. It is also common to smell burning dust when you turn on your furnace after months of inactivity. Dust can build up in your ducts, and become ignited when you turn the furnace on. The burnt dust smell should only linger around for a couple of hours. If you smell rotten eggs or sulfur coming from your furnace, you might have a gas leak. Natural gas contains additives to give it a distinct smell to alert people of it;s presence. If you smell sulfur or rotten eggs coming from your furnace, you should turn off your furnace, and contact your HVAC provider right away.


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