The study of the residence time distribution is usually made in order to diagnose the hydrodynamic behaviour of the equipment. This paper reports on the residence time distribution according to six combinations of the open and closed boundary conditions, which are compared in order to determine an appropriate equation to fit experimental data from the stimulus-response method. The residence time distribution under laminar flow is analysed and the mathematical modelling of the pure convection regime, zone of axial dispersion and intermediate case is discussed. The disturbances in the residence time distribution produced by a non-ideal impulse and also by the dynamic behaviour of the sensor are quantified and the errors in its evaluation are given. (C) 2015 Elsevier Ltd. All rights reserved.