Abstract: The heating stove comprises from top to bottom, a smoke space, an oven, a combustion chamber and an ash-pit; a grate separates the chamber from the ash-pit. The grate comprises a plurality of open-ended hollow cylindrical metallic ducts which criss-cross so as to form a X and which open outwardly of the stove for heating ambient air circulating therethrough. Each of the ducts has a substantially-flattened crossing portion, in order to reduce the spacing between the tubes. The grate may support a solid combustible, but permit the ashes to drop into the ash-pit between the ducts. A plurality of upright semi-cylindrical tubes are fixed to the sides of the oven and form passages between the combustion chamber and the smoke space. The oven is heated not only at its bottom but along its side walls and the tubes also serve to heat the ambient air.