When we look at the interior of the same chimney we can find a number of imperfect conditions. Pieces are missing from the original clay liner and there are cracks in the clay liner. (Old chimneys might not even have a liner.) Mortar and bricks are loose and falling. And there is excessive buildup of combustible creosote on the flue walls. These conditions are the result of a number of possible causes, including: flue fires, an improperly vented or misused stove, poor construction, excessive moisture, and more. With continued use, any of these conditions could lead to loss of property or life.