Chimney draft is that upward movement of air within the chimney that is necessary to support the efficient exhausting of flue gasses to the outside. It can be affected positively or negatively by a number of things.
Stainless steel pipe, either rigid or flexible, made for relining flues of masonry chimneys when the original clay liner has cracked or broken. May also be used to create a lining in a masonry chimney that was made without a clay liner.
Protective coverings for chimneys usually made of aluminum, galvanized or stainless steel, or copper. Most chimney caps have a mesh screening that serves the dual purpose of spark arrestor and barrier against animals. Chimney caps also prevent rain from entering the flue of the chimney.
A device installed at the top of a chimney for the purpose of sealing the flue shut when the fireplace is not in use. They are often used as replacements for throat dampers that are installed just above the firebox when a masonry chimney is built. Lyemance and Lock-Top top-sealing dampers are as much as 90% more efficient than throat dampers because they provide a silicone rubber gasket seal rather than metal to metal.