Definition for word: Flue

An enclosed passageway for directing products of combustion to the atmosphere. A large pipe through which fumes escape from a combustion appliance or fireplace. Metal flue pipes are typically double walled galvanized or stainless steel metal. A fireplace flue can be triple-walled steel or made from ceramic flue tile.

Referrence from

A flue is a duct, pipe, or chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. In the U.S.A., for water heaters and modern furnaces they are also known as 'vents' and for boilers as 'breeching'. They usually operate by buoyancy, also known as the stack effect, or the combustion products may be 'induced' via a blower. As combustion products contain carbon monoxide and other dangerous compounds, proper 'draft', and admission of replacement air is imperative. Building codes, and other standards, regulate their materials, design, and installation.

View this term in Wikipedia