In an embodiment a device includes a first housing in which a piezoelectric transformer is arranged and a second housing in which a control circuit is arranged, the control circuit configured to apply an input voltage to the piezoelectric transformer, wherein the piezoelectric transformer is configured to ionize a process medium, and wherein the device is configured to provide a circulating air operation so that the process medium is guided from the piezoelectric transformer through a catalytic converter and then back to the piezoelectric transformer and generate a non-thermal atmospheric pressure plasma.