flue

This term refers specifically to the internal passage of a chimney or industrial exhaust system. It is often confused with the word flu, which refers to the influenza virus, though they are phonetically identical. In a domestic setting, the flue is the actual pipe that carries smoke away, whereas the chimney is the overall structure containing it. In industrial contexts, the term extends to larger conduits used in kilns or smelting furnaces. These structures are engineered to manage high-temperature waste gases and often require specialized linings to prevent chemical erosion or heat damage.