Abstract: An end wall of a horizontally extending coking chamber is provided with an opening through which a reciprocatable leveling rod projects with clearance into the chamber for leveling coal fed thereinto. Channel means communicating at one end with this opening surround with clearance the portion of the leveling rod outside the chamber. Air under pressure is fed into the region of the outer end of the channel means and sucked out from the latter from the region of the one end to thereby prevent gas to pass through the clearance between the rod, the opening in the wall and the channel means to the outside of the coking oven without feeding any of the air into the chamber.