Abstract: A germicidal device includes a lighting member operably in an on-state in which the lighting member emits ultraviolet light for killing microorganisms, or in an off-state in which the lighting member emits no light; a sensing member operably detecting at least one event occurred in an area; and a microcontroller unit coupled with the lighting member and the sensing member for controlling operations of the lighting member in a respective state in accordance with the at least one event occurred in the area. The at least one event includes a movement in the area, an acoustic wave in the area, an intrusion into the area, an expiration of an on-state time period in which the lighting member is in the on-state, an expiration of an off-state time period in which the lighting member is in the off-state, and/or an instruction from a remote operation.