As a general rule, when you smell something weird, it is a signal that there is something wrong somewhere. This is true whether it is burning rubber as you are driving down the road or old food in the kitchen. In the same way, when you smell something funny coming from your heating system when you switch the heat on, you can bet that there is something strange occurring from within the furnace. This means that you need to get in touch with a professional sooner rather than later to come out, diagnose the issue, and resolve the problem before something more serious occurs. While the odor could simply be a result of a dirty filter, it could also be a signal that there is a more serious problem at play.

Do You Smell Rotten Eggs?

When you switch on your furnace and the smell of rotten eggs knock you over, there is a chance that there is a gas leak. You will want to turn off all of your appliances immediately, open up your windows and doors so that the gas can escape the home, and exit the building immediately. Use a cell phone or go to a neighbor's house to contact 911 and a furnace repair company, as this type of repair is far beyond your expertise.

Do You Smell Metal or Plastic Burning?

When you turn your furnace on or while it is running you smell metal or plastic burning, this is a sign that there is an electrical wiring issue or that there is an interior component overheating. The odor could also signal that there is a foreign object lodged in the ducting and is in the process of burning. You will need to switch off the heating system and contact a repair professional so that an inspection of the ducting and electrical components of the furnace can be performed.

Do You Smell Dust or Mold?

The first time that you turn your furnace on during the fall is going to result in a strange odor—likely a dusty or moldy smell. Over the several months of spring and summer when you are not using the furnace, dust, dirt, and pollen will accumulate in the ducting. So, when you turn the furnace on for the first time, it all burns. This is completely normal. However, the odor should not continue. If the dusty or moldy odor persists, the filter likely needs to be changed. If a new filter does not resolve the smell, contact a professional.

When you are dealing with furnace smells or other issues, contact a furnace repair company in your area.