What’s That Funny Smell When the Furnace Turns On?

In Denver, we can experience summer one day and fall the next. Many of us try to hold on to that warm weather feeling as long as possible, and finally making the decision to switch on the heat when the temperature drops is practically a fall ritual. In many homes, that ritual is accompanied by a distinctive smell when the furnace kicks on for the first time. What is that smell and should it concern you? Does it mean your furnace is in need of repair?

3 Types of Smells

Furnace smells do not always indicate a problem, but they should never be ignored. Typically, they fall into 3 categories:

1. Musty or burning dust

The burning dust smell is most often the result of dust collecting in the furnace over the summer. Once the system is turned on, it usually dissipates in a day or so. Changing out the old furnace filter at the start of the season can help the smell disappear more quickly. A musty smell could be coming from mold in the furnace filter or, if you have one, the humidifier filter. Replace the humidifier filter every season to prevent this. If either of these smells persist, however, you may have a more serious problem. Call your HVAC professional for help.

2. Burning electrical parts

This type of smell could be caused by something serious such as a motor overheating or a cracked heat exchanger. In this case, turn the unit off, unplug it and call your HVAC professional for an inspection and repair as soon as possible. Once the issue is addressed, continue to monitor the furnace for a few hours to be sure there are no fires or other problems.

3. Rotten egg

The rotten egg or sulfur smell is added to natural gas and propane to alert you to a leak. A gas leak is extremely serious because it can cause an explosion or fire. Evacuate your home immediately. When you are safely away from your home, call the fire department and utility company for assistance.

If your furnace is more than 8 years old, carbon monoxide (a deadly odorless and colorless gas) is also a potential risk. Have your furnace inspected each year before you need to use it to ensure that it is working properly, minimize costly repairs, keep utility costs low and prolong the life of the unit.

Keep your home and family safe and comfortable this fall and winter. Contact IAQ to schedule your annual furnace inspection today!