Heating device by combustion of a solid fuel, comprising a combustion chamber comprising: - a front wall that is normal to a vector of depth Y and comprises an opening for the insertion of fuel that can be closed by a door, - a plate that is normal to a vertical vector Z, able to support the solid fuel, and preferably comprises a grate primary air intake orifice configured to allow a grate primary air flow to enter into the combustion chamber, a direct orthonormal basis being formed by a side vector X, the vector of depth Y and the vertical vector Z, - a left side wall that is normal to a left normal vector L orthogonal to the vertical vector Z, an orientation angle of the left side wall α measured from the side vector X to the left normal vector L in the trigonometric direction being comprised between -30° and 0°, preferably equal to 0°, - a right side wall that is normal to a right normal vector R orthogonal to the vertical vector Z, an orientation angle of the right side wall β measured from the side vector X to the right normal vector R in the trigonometric direction being comprised between -180° and -150°, preferably equal to -180°, - an upper wall that is normal to an oblique vector W orthogonal to the side vector X, an inclination angle of the upper wall γ measured from the vertical vector Z to the oblique vector W in the trigonometric direction being comprised between 100° and 180°, preferably between 110° and 160°, preferably between 120° and 150°, the upper wall being adjacent to the left and right side walls, - a rear wall that is normal to a vector -Y opposite the vector of depth Y and adjacent to the plate and to the left and right side walls, - an interstice being present between the rear wall and the upper wall and which preferably extends from the left side wall to the right side wall, the interstice being closed by, - a mechanical assembly, preferably made of metal, preferably made of stainless steel, comprising a channel passing through the interstice and configured to allow a secondary air flow to pass through the channel from an entry opening of the channel to a secondary air intake orifice in the combustion chamber, characterized in that the secondary air intake orifice in the combustion chamber has an extended shape substantially parallel to the side vector X and that extends from: - a left end of the secondary air intake orifice located at a distance comprised between 0 cm and 1 cm from the left side wall, said distance being measured parallel to the side vector X, and to - a right end of the secondary air intake orifice located at a distance comprised between 0 cm and 1 cm from the right side wall, said distance being measured parallel to the side vector X, and in that the mechanical assembly is configured so that the secondary air flow supplying the combustion chamber extends continuously between the vicinity of the left side wall and the vicinity of the right side wall. - a front wall that is normal to a vector of depth Y and comprises an opening for the insertion of fuel that can be closed by a door, - a plate that is normal to a vertical vector Z, able to support the solid fuel, and preferably comprises a grate primary air intake orifice configured to allow a grate primary air flow to enter into the combustion chamber, a direct orthonormal basis being formed by a side vector X, the vector of depth Y and the vertical vector Z, - a left side wall that is normal to a left normal vector L orthogonal to the vertical vector Z, an orientation angle of the left side wall α measured from the side vector X to the left normal vector L in the trigonometric direction being comprised between -30° and 0°, preferably equal to 0°, - a right side wall that is normal to a right normal vector R orthogonal to the vertical vector Z, an orientation angle of the right side wall β measured from the side vector X to the right normal vector R in the trigonometric direction being comprised between -180° and -150°, preferably equal to -180°, - an upper wall that is normal to an oblique vector W orthogonal to the side vector X, an inclination angle of the upper wall γ measured from the vertical vector Z to the oblique vector W in the trigonometric direction being comprised between 100° and 180°, preferably between 110° and 160°, preferably between 120° and 150°, the upper wall being adjacent to the left and right side walls, - a rear wall that is normal to a vector -Y opposite the vector of depth Y and adjacent to the plate and to the left and right side walls, - an interstice being present between the rear wall and the upper wall and which preferably extends from the left side wall to the right side wall, the interstice being closed by, - a mechanical assembly, preferably made of metal, preferably made of stainless steel, comprising a channel passing through the interstice and configured to allow a secondary air flow to pass through the channel from an entry opening of the channel to a secondary air intake orifice in the combustion chamber, - a left end of the secondary air intake orifice located at a distance comprised between 0 cm and 1 cm from the left side wall, said distance being measured parallel to the side vector X, and to - a right end of the secondary air intake orifice located at a distance comprised between 0 cm and 1 cm from the right side wall, said distance being measured parallel to the side vector X,