Infrared thermography was used to study the formation and dynamics of hot zones on top of a shallow packed bed reactor in which CO was oxidized by spherical Pd/Al2O3 catalytic pellets. The impact of global coupling between the gas on top of the bed and the catalyst was studied by changing the residence time of the gas. The global coupling had a strong impact on the selection, dynamics and stability of the observed hot zone motions (breathing, anti-phase and rotation). (c) 2005 Elsevier Ltd. All rights reserved.