How to Fix Soot Coming From Oil Furnaces

Open the inspection door to the combustion chamber of the furnace. If you can hold your hand at the opening comfortably, the source of the problem probably is not a blockage. If there is excessive heat in that area, a clog in the system is likely, and the furnace and chimney need to be cleaned.

Check the gaskets located around the inspection door of the furnace. If the gaskets are looking warped or if you see cracks in them, they need replacing and are the likely cause of the excess soot.

Examine the heat exchanger of the furnace to look for cracks as well. If the heat exchanger is cracked, you'll likely need a new furnace and the current one will continue to burn improperly and create more soot until it is replaced.

Listen to the furnace as it runs. If you hear any unusual noises such as shrieking or banging, the furnace may have a bad belt or bearing and this requires immediate professional repair.