Forces on a single horizontal slat immersed in a fluidized bed of Geldart A particles were investigated for the purpose of providing useful design guidelines for long-period reliability of horizontal baffles in industrial reactors. The characteristics of slat forces in the fluidized and de-fluidized states of a reactor were measured using adhered strain gauges. The main parameters influencing these characteristics were superficial gas velocity, installation height, inclination angle, and method of slat installation. The experimental results show that the measured force on the slat in the fluidized state is highly fluctuating, but its root-mean-square is usually significantly lower than for the de-fluidized state, especially at the bottom of the bed. The effects of various operating and structural parameters were determined. Critical locations and operating conditions under high load are indicated and warrant more attention in structural design of horizontal baffles. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.