Ultraviolet sensing apparatus

UV sensing apparatus comprising a housing which is substantially opaque to electromagnetic radiation, an aperture formed in the housing, a filter positioned within the housing at the internal mouth of the aperture, a fluorescent member positioned within the housing on that side of the filter remote from that adjacent to the aperture, and a light sensor positioned within the housing to receive light emitted by the fluorescent member, wherein the filter is such that it substantially removes visible light, the fluorescent member is such as to fluoresce when subjected to UV radiation, and the light sensor is positioned so that, without the provision of a second filter, substantially none of any electromagnetic radiation entering the housing via the aperture impinges upon the light sensor, and wherein the internal geometry of the apparatus and the size of the aperture are such as to constrain the angles of electromagnetic radiation entering the apparatus so that IR radiation is not reflected internally within the fluorescent member at angles which allow the IR radiation to egress towards the light sensor.