The function of a flue in a chimney is to contain combustion products. A flue serves as the pathway for exhaust gases and smoke produced by the combustion of fuels in a fireplace, furnace, or stove to exit the home safely. It is designed to capture these products to prevent them from entering the living space, thereby protecting the occupants from harmful fumes like carbon monoxide and other toxic gases.
The flue must be properly constructed and maintained to ensure that it works effectively, which includes being sealed well enough to contain heat and gases while allowing for adequate ventilation. This critical function helps maintain safety and indoor air quality, making it an essential component of any chimney system.
Other aspects, such as airflow enhancement or structural support, do not primarily pertain to the flue's core function. While insulation may be important for overall chimney efficiency, it is separate from the primary role of the flue itself.