An arrangement in combustion chambers for burning solid fuel, such as wood, wood chips, pellets, coal and sundry waste, with recirculation combustion and including a combustion chamber (1) with fire bars (5) arranged in its lower part, a convection section (12), a flue gas outlet (13) and normally a fan for supplying alternatively air or an air-flue gas mixture. What is primarily characterizing for the invention in this arangement is that it further contains a first supply conduit (18) from the pressure side of the fan (15) arranged with its outlet in a pressure chamber (19) situated under the fire bars (5) in the combustion chamber (1), a second supply conduit from the pressure side of the fan to the combustion chamber, the outlet of this conduit being arranged above the fire bars and having the shape of a gap (27) arranged completely or partially surrounding the fire in the combustion chamber, and there possibly also being a return conduit (21) connected to the suction side of the fan for recirculating flue gases from the flue gas outlet (13) to the combustion chamber.