Sulfur dioxide (SO2) is a common atmospheric contaminant which has a deleterious effect on performance of fuel cells. In the present paper, we are reporting the performance of a proton exchange membrane fuel cell (PEMFC) stack exposed to SO2 as a contaminant, introduced in air stream and the process of recovery. The stack is exposed to a non-continuous step wise poisoning of 10ppm of SO2 in air for about 100 minutes. The response of stack to the contaminant exposure is observed to understand the immediate effect of SO2 on stack performance and its distribution profile among individual cells. Successive polarization recovery technique, by cycling between two voltages, is adopted to recover the stack after contamination. The sulfur adsorption onto platinum can also be associated to weak and strong adhesion of sulfur species leading to drop in catalyst utilization. The recovery suggests that the sulfur is irreversibly adsorbed on to platinum sites at low current density regions. However, at higher current densities, in the presence of H2O, this undergoes rapid hydrolysis to form H2SO4, leading to partial recovery. The recovered performance of the stack is also presented. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim