A chimney flue pipe is used to carry the gases and smoke produced from your fireplace or wood-burning stove to the outside. Your chimney flue pipe lives inside of your chimney and is usually lined by materials, such as clay or steel, to help insulate and stand the test of time. If there is damage to your flue pipe such as cracks, these harmful gases and smoke produced by your fire can escape into your home and cause even more harm to your home and the people living in it.