A flue is a duct or pipe that allows smoke and gases to escape from a fireplace, stove, or furnace to the outside atmosphere. It is an essential component of heating systems, ensuring that harmful fumes do not enter living spaces. Proper ventilation through a flue helps maintain indoor air quality and safety. Flues can be made from various materials, including metal and clay, and come in different shapes and sizes depending on the appliance they serve. Regular maintenance and cleaning of a flue are important to prevent blockages and reduce the risk of chimney fires, especially in structures with chimneys.