A flue is a duct or pipe that allows smoke and gases from a fireplace, furnace, or stove to escape safely outside a building. It helps to vent harmful emissions, ensuring that indoor air remains clean and safe for occupants. Flues are commonly found in homes with heating systems that burn fuel, such as wood, coal, or gas. Flues can be made from various materials, including metal and clay, and are designed to withstand high temperatures. Proper installation and maintenance of a flue are essential to prevent chimney fires and ensure efficient operation of heating appliances like fireplaces and wood stoves.