Abstract: A downdraft stove with a conical reaction chamber surrounded by a heat-insulating mass is disclosed. A tubular grating installed in the reaction chamber has a substantially vertically oriented central tube open at its upper end and connected at its lower end to an air inlet opening, and a cap supported above the open upper end, the space between the cap and the upper end constituting a primary air inlet nozzle. A plurality of grating tubes are radially distributed around and take off substantially horizontally from and communicate with the central tube, thereby defining a grating, and then turn downwardly into a conical shape conforming to the reaction chamber shape and are open at their downward ends to thereby constitute secondary air inlets. The downward-projecting ends of the grating tubes are twisted about the axis of the central tube in order to induce a swirling air flow pattern in the reaction chamber.