A method for sterilizing ambient air includes the steps of: a) installing a plasma-based smart window including an atmospheric pressure plasma device which includes first and second transparent flat patterned electrodes sandwiched between a light-transmissive substrate and a light-transmissive cover plate; and b) applying a power supply parameter of a predetermined magnitude between the first and second transparent flat patterned electrodes at ambient temperature and pressure to generate a surface plasma proximate to the light-transmissive substrate or the light-transmissive cover plate so as to inactivate microorganisms in the ambient air.