Abstract: A jumper pipe forms a passageway between the free spaces above coal charges in adjacent coking chambers for the natural flow of relatively cooler coke oven gas from the free space above the coal charge in the most recently charged one of the coking chambers into the free space above the coal charge in the other of the coking chambers to reduce the relatively higher temperature therein. An inert atmosphere is maintained along at least part of the passageway to prevent the flow of coke oven gas essentially during decarburization and the pushing of coke from either of the two adjacent coking chambers. Valve members at opposite end portions of the jumper pipe are moved to at least partially-closed positions to facilitate the maintenance of an inert atmosphere therein. A supply or steam or gaseous nitrogen is used to maintain the inert atmosphere in the jumper pipe. The inert gas prevents the entrance of coke oven gas into a coking chamber while undergoing decarburization.