Chimney

A chimney is a system for venting hot gasses and smoke from a stove[?], furnace or fireplace[?] to the outside of a building. They are typically almost vertical to ensure the hot gasses flow smoothly, drawing air into the combusion through convection.

Chimneys were traditionally built of brick, both in small and large buildings. Due to brick's limited ability to handle traverse loads, chimneys in houses were often build in a "stack", with a fireplace on each floor of the house sharing a single chimney, often with such a stack at the front and back of the house. Today's central heating[?] systems have made chimney placement less critical, and the use of non-structural double-wall metal piping allows it to be bent around obstructions and through walls.

Industrial chimneys were typically external structures, as opposed to being built into the wall of a building. Most often they were located near a central boiler, and the gasses carried to it with external ductwork. Today the use of single-pour concrete has almost entirely replaced brick in this role.

A characteristic problem with chimneys is they develop deposits of creosote on the walls of the structure. This deposits of this substance can interfere with the airflow and more importantly they are flamable and can cause dangerous chimney fires if the deposits ignite in the chimney. Thus, it is recommended that chimneys be cleaned on a regular basis to prevent these problems. The workers who perform this task professionally are called chimney sweeps