A flue baffle may be removed from the narrow end of a frusto-conical flue. The baffle has a plurality of hinged plates secured to a tube, and slots in the tube beneath each plate. A slidable rod extends through the tube and has a plurality of pins which extend through the slots and contact the plates. When the rod slides down, the pins also descend, and the plates collapse. When the rod is lifted upwardly, the pins push the plates apart. A dowel may be secured to the tube to communicate with the rod to secure the rod in relation to the tube and spread the plates at a pre-determined point. The width of the plates is smaller than the narrow end of the flue so that the baffle may be removed when the plates are collapsed. The plates may be skewed on the tube so that all of the gases and heat which rise through the flue are diverted toward the flue wall by at least one of the plates without excessively obstructing the flow of gases out of the flue.