Abstract: Apparatus for burning combustible particles to heat circulated air. The apparatus includes an upright housing containing a removable liner which forms the combustion chamber of the burner, and a perforated, intermediate wall member which forms, with the walls of the housing and the liner, outer and inner gas-receiving spaces, respectively. Air injected into the housing passes from the outer, into the inner gas-receiving space, where the gas is directed, through tuyeres in the liner, into the chamber, substantially tangentially to the wall thereof, producing a gas vortex therein. Particles introduced into the chamber through an upper opening are combusted primarily in the chamber's upper core region with such combustion being supported by, and acting to heat, vortexing gas within the chamber prior to its discharge through a lower chamber opening.