In many cement plants, a calciner with secondary firing is interposed between the preheater and the rotary kiln. To optimise the calciner and avoid caking, the process gas components in the kiln exhaust gas are continuously monitored. Due to the process conditions, a hot-measuring analysis system with a back-flushable gas sampling probe - the MCS300P HW process gas analysis system - is suitable for this purpose. The system enables simultaneous measurement of up to 6 components plus O2. If the SNCR process for flue gas denitrification is also used in the calciner, the system can be used to monitor ammonia slip and NOx concentrations. Depending on the plant, the measuring point is located at a suitable point between the outlet of the calciner and the outlet of the preheater.