Chemical companies face a major transition as the current workforce ages and the number of retirements accelerates resulting in many years of lost operating experience. It will be challenging to maintain and improve the reliability and safety of operations as some of the best operators leave the workforce. Faults due to operator errors can be addressed by improving the operator's training and increasing the robustness of the control system to operator variability. In this article, we demonstrate how operator variability can be detected as a first step toward measuring and improving the control system's robustness. The characterization of a typical operator procedure caused transition, a reflux pump switch, and the resulting control system response was analyzed using the dynamic process simulation tool Honeywell UniSim Design. The best operator response and potential errors for other daily operator activities such as pump switches, reboiler switches, and similar operational transitions can be obtained offline by studying process history. (c) 2014 American Institute of Chemical Engineers Process Saf Prog 33: 333-338, 2014