Abstract: A burner is of generally tubular configuration, and comprises an inner shell and an outer shell. The inner shell has therein a nozzle, an ignition electrode, and a sight tube. An annular gap is provided between the two shells, through which a comburant-gas flows to an annular, inwardly directed and constricted discharge opening, with swirl blades upstream of the discharge opening. A comburant-gas supply passes through openings in the inner shell upstream of a baffle which is positioned transversely of the inner shell, and which has radial slots therein inclined to the plane of the baffle to cause swirling of comburant-gas passing through the slots in the baffle. A toroidal-cyclone combustion zone is created due to the slots in the baffle creating a swirling downstream flow downstream of the baffle, and the inwardly directed annular and constricted opening, which aspirates comburant-gas which has passed through the baffle.