the coking apparatus employed in the practice of the invention is adapted to receive coal preheated to a temperature of about 160 u00b0 c to 280 u00b0 c and above the coking apparatus is of the by product type having collecting mains 59 fig2 connected to the coking chambers through a suction port 58 in each chamber or alternatively the collecting main 59 is disconnected and the coking chambers are connected through a suction opening 57 in each to a collecting conduit 54 and to an independent fume cleaning or scrubbing system not shown through a closure means 53 turning to fig2 and particularly the upper part thereof it will be seen that two coal feeding systems are shown the system feeding coking chambers 1 5 inclusive and 11 15 inclusive in fig1 being shown in full lines to the right and the system feeding coking chambers 6 10 inclusive being shown at the left the lower portion of such latter feeding system being shown in dash lines sources of neutral gas under pressure are provided one such source 74 fig1 being provided for the right hand coal feeding system of fig2 and a second source of neutral gas under pressure designated 75 being provided for the left.