Procedure for the detection of buildup in a vessel in which a radiometric measuring unit is provided for the measurement and/or monitoring of a measured variable, particularly a level or a density (e), of a product in the vessel, - wherein, during operation, said measuring unit emits radioactive radiation along a measurement radiation path (A, A') through the vessel, measures a radiation intensity (I A) exiting the vessel along the measurement radiation path (A, A'), and determines a measurement result that corresponds to the measured variable using calibration data of the measuring unit, which are determined when there is no buildup in the vessel, and using the measured radiation intensity (I A), wherein - using a reference measuring unit, radioactive radiation is transmitted along a reference radiation path (B, B', C) through the vessel, a radiation intensity (I B) exiting the vessel is measured along the reference radiation path (B, B', C), and a measurement result that corresponds to the measured variable is determined using calibration data of the reference measuring unit, which are determined when there is no buildup in the vessel and using the measured radiation intensity I B, - wherein the reference radiation path (B, B', C) extends through the vessel in such a way that - when a layer of deposit buildup is present on the inner walls of the vessel - a ratio of a sum of the two segments (A1, A3) of the measurement radiation path running through the layer of deposit buildup to the length of another segment of the measurement radiation path (A, A') running between these two segments (A1, A3) differs from the ratio (VB, VC) calculated in the same way for the reference radiation path (B, B',C), wherein - on account of the calibration of the measuring unit and the reference measuring unit when there is no buildup in the vessel - the measurement results of the two units when there is no buildup in the vessel correspond to one another within the range of the achievable measuring accuracy, and - the presence of deposit buildup is detected on the basis of deviations, determined during operation, between the measurement results of the measuring unit and the measurement results of the reference measuring unit. - wherein, during operation, said measuring unit emits radioactive radiation along a measurement radiation path (A, A') through the vessel, measures a radiation intensity (I A) exiting the vessel along the measurement radiation path (A, A'), and determines a measurement result that corresponds to the measured variable using calibration data of the measuring unit, which are determined when there is no buildup in the vessel, and using the measured radiation intensity (I A), wherein - using a reference measuring unit, radioactive radiation is transmitted along a reference radiation path (B, B', C) through the vessel, a radiation intensity (I B) exiting the vessel is measured along the reference radiation path (B, B', C), and a measurement result that corresponds to the measured variable is determined using calibration data of the reference measuring unit, which are determined when there is no buildup in the vessel and using the measured radiation intensity I B, - wherein the reference radiation path (B, B', C) extends through the vessel in such a way that - when a layer of deposit buildup is present on the inner walls of the vessel - a ratio of a sum of the two segments (A1, A3) of the measurement radiation path running through the layer of deposit buildup to the length of another segment of the measurement radiation path (A, A') running between these two segments (A1, A3) differs from the ratio (VB, VC) calculated in the same way for the reference radiation path (B, B',C), wherein - on account of the calibration of the measuring unit and the reference measuring unit when there is no buildup in the vessel - the measurement results of the two units when there is no buildup in the vessel correspond to one another within the range of the achievable measuring accuracy, and - the presence of deposit buildup is detected on the basis of deviations, determined during operation, between the measurement results of the measuring unit and the measurement results of the reference measuring unit.