A carbon monoxide oxidation device for oxidizing carbon monoxide contained in a hydrogen rich reformat gas includes a housing, wherein the housing incorporates an oxidation catalyst, which is adapted to oxidize the carbon monoxide of the reformat gas by an oxidizing agent to carbon dioxide, includes upstream of the catalyst at least one gas inlet for providing a gas stream of at least the reformat gas into the housing, includes downstream of the catalyst a gas outlet for exiting treated gas from the housing, and incorporates a gas stream perturbation device which is arranged upstream of the catalyst and which is adapted to provide a perturbation in the gas stream, wherein the gas stream perturbation device is designed as at least one propeller-shaped plate with a plate portion having a surface facing the gas stream and at least one blade which is connected to the plate portion and has a leading edge and an effluent edge, wherein a surface defined between leading edge and effluent edge is inclined in relation to the surface of the plate portion with a predetermined blade inclination angle, thereby defining at least one opening in the plate.