out in accordance with the standard part of the control mode fixed setting facilities either with a setting device for all fire shafts or individual devices for each fire shaft are mounted on the suction unit 60 the setting facilities are usefully fixed in advance by the plant operation system and adjusted to suit the negative pressure conditions at certain intervals of time in response to new measurements the changes in negative pressure which are likewise given by the process control system are brought about via the regulating facilities 85 86 87 88 fig2 e g slides on side b if the effect of these alterations is inadequate then the setting of the suction unit must be changed fig3 b shows two chambers 61 62 of the pre heating zone on side a and two chambers 63 64 of the pre heating zone on side b along with the baking chambers in this fire reversal situation the changes in the amount of gas are made in accordance with the standard part of the model the changes in negative pressure are made for the chambers on side a via the settings on the suction unit and for the chambers on side b via the regulating facilities 85 86 87 88 in the wall 73 on side b next to the fire reversal unit if as shown in fig3 c and fig2 the first three chambers 61 62 63 of the pre heating zone are already on side a and only the last chamber 64 of the.