Dosed proportioning and cutoff of combustion air into the primary heating space of a horizontal coke oven is provided by apertures in the ceiling of the coke oven chamber, the apertures covered with a withdrawable cover device which controls the amount of air admitted, manually or in an automatic mode. By way of this device, ventilation of a coke oven chamber with primary air can be so controlled that primary air is introduced in an exactly dosed manner and, depending on its place of installation, exactly distributed into the primary heating space of a coke oven chamber.