An ultraviolet light generating unit for use in an enclosed space, the unit comprising: a housing including a shell with an aperture; a shutter movable between a first position in which the shutter covers the aperture and a second position in which the shutter exposes a majority of the aperture; a UV light source positioned within the housing and configured to generate radiation in the UVC band of the electromagnetic radiation spectrum through the aperture when the shutter is in the second position; a memory element configured to store electronic data; and a processing element electronically coupled with the memory element and configured to - receive a first signal from a room occupancy sensor, the first signal indicating that the enclosed space is either occupied or unoccupied, and generate a second signal to be used to move the shutter to the first position when the first signal indicates that the enclosed space is occupied and to the second position when the first signal indicates that the enclosed space is unoccupied; characterised in that the processing element is further configured to receive a third signal from a door sensor, the third signal indicating that a door providing access to the enclosed space is either open or closed, and generate the second signal to be used to move the shutter to the first position when the first signal indicates that the enclosed space is occupied or the third signal indicates that the door is open and to the second position when the first signal indicates that the enclosed space is unoccupied and the third signal indicates that the door is closed. a housing including a shell with an aperture; a shutter movable between a first position in which the shutter covers the aperture and a second position in which the shutter exposes a majority of the aperture; a UV light source positioned within the housing and configured to generate radiation in the UVC band of the electromagnetic radiation spectrum through the aperture when the shutter is in the second position; a memory element configured to store electronic data; and a processing element electronically coupled with the memory element and configured to - receive a first signal from a room occupancy sensor, the first signal indicating that the enclosed space is either occupied or unoccupied, and generate a second signal to be used to move the shutter to the first position when the first signal indicates that the enclosed space is occupied and to the second position when the first signal indicates that the enclosed space is unoccupied; characterised in that the processing element is further configured to receive a third signal from a door sensor, the third signal indicating that a door providing access to the enclosed space is either open or closed, and generate the second signal to be used to move the shutter to the first position when the first signal indicates that the enclosed space is occupied or the third signal indicates that the door is open and to the second position when the first signal indicates that the enclosed space is unoccupied and the third signal indicates that the door is closed. receive a first signal from a room occupancy sensor, the first signal indicating that the enclosed space is either occupied or unoccupied, and generate a second signal to be used to move the shutter to the first position when the first signal indicates that the enclosed space is occupied and to the second position when the first signal indicates that the enclosed space is unoccupied; characterised in that the processing element is further configured to receive a third signal from a door sensor, the third signal indicating that a door providing access to the enclosed space is either open or closed, and generate the second signal to be used to move the shutter to the first position when the first signal indicates that the enclosed space is occupied or the third signal indicates that the door is open and to the second position when the first signal indicates that the enclosed space is unoccupied and the third signal indicates that the door is closed.