The development of a side-stream reverse osmosis cell, called the 'canary cell', to simulate the spiral wound module (SWM) is described. Representative fouling rates and ex-situ membrane autopsies show the capability of the canary cell to simulate the SWM under controlled hydrodynamics and flux conditions. The development of a dimensionless calibration curve allows the canary cell to act as an early warning system with respect to the SWM. The rate of cake thickness increase was also measured by ultrasonic time domain reflectometry coupled to the canary cell and used to monitor membrane fouling and cleaning. (C) 2015 Elsevier B.V. All rights reserved.