Due to the wide applications of acetonitrile as a solvent in the chemical industry, acetonitrile can be present in the air and should be considered a possible pollutant. In this work, the spatial proton exchange membrane fuel cell performance exposed to air with 20 ppm CH3CN was studied using a segmented cell system. The injection of CH3CN led to performance losses of 380 mV at 0.2 A cm(-2) and 290 mV at 1.0 A cm(-2) accompanied by a significant change in the current density distribution. The observed local currents behavior is likely attributed to acetonitrile chemisorption and the subsequent two consecutive reduction/oxidation reactions. The hydrolysis of CH3CN and its intermediate imine species resulted in NH4+ formation, which increased the high-frequency resistance of the cell and affected oxygen reduction and performance. Other products of hydrolysis can be oxidized to CO2 under the operating conditions. The reintroduction of pure air completely recovered cell performance within 4 h at 1.0 A cm(-2), while at 0.2 A cm(-2) the cell recovery was only partial. A detailed analysis of the current density distribution, its correlation with spatial electrochemical impedance spectroscopy data, possible CH3CN oxidation/reduction mechanisms and mitigation strategies are presented and discussed. (C) 2015 Elsevier B.V. All rights reserved.