What is a common sign of a chimney blockage?

A common sign of a chimney blockage is the presence of dark, sooty buildup near the cap. This buildup occurs when creosote and soot accumulate due to incomplete combustion of fuels like wood. When a chimney is functioning properly, smoke and combustion byproducts should flow up and out, but if there's a blockage, these materials can collect at the top or along the flue, leading to visible residue. Not only does this indicate a blockage, but it also poses serious safety risks, including the potential for chimney fires or dangerous carbon monoxide buildup in the home. Recognizing such signs can prompt timely cleaning or professional inspection to ensure safe operation.