Abstract: The gas heating device comprises: a heat exchange tube (20); a gas chamber (30) provided with a pressurized gas inlet (31) and with gas injection nozzles (40) turned and open to an inlet end (21) of the heat exchange tube (20). Each gas injection nozzle (40) has only one inlet (41) open to the gas chamber (30), and one outlet (42) with its axis (Y) lying on a vertical plane (P) containing the horizontal axis (X) of the heat exchange tube (20), each gas injection nozzle (40) being associated with a deflector (50) affixed to the gas inlet chamber (30) and having an inclined deflecting plate (52) sectioned by the axis (Y) of the outlet (42) of the respective gas injection nozzle (40), said deflector (50) of one gas injection nozzle (40) being disposed on a side of the vertical plane (P) opposite to the side on which is provided the deflector (50) of an adjacent gas injection nozzle (40), an outlet end (22) of the heat exchange tube (20) being partially blocked by a deflecting cover (60).