Chimney is a vertical structure, forming a tunnel or passage in which smoke, gases, powders, etc., can be carried off. It can be directly connected to a machine or be separated and is usually wider at the bottom, so it can overlap the space where the smoke of the burning material escapes. This creates a draft that sends the gases upwards and out. The top part is on the outside of the building and usually rises above a roof.
The top photos show chimneys which are attached to kilns.
The bottom photos show two kinds of chimneys; outside and inside a building.
Read more about: Kiln – Ventilation