Abstract: An apparatus for disinfecting an air space is presented. The apparatus includes a housing having a front surface, a back surface, a top surface, a bottom surface, a first end, and a second end. A light emitting diode is inside the housing and configured to emit ultraviolet radiation, at least 90% of which has a wavelength less than 280 nm, in a direction away from the housing into surrounding space. Circuits inside the housing control the light emitting diode to emit radiation at different intensity levels including zero. Motion sensors may be coupled to the circuits to turn the light emitting diode on and off and modulate the intensity of radiation that is emitted, thereby avoiding exposing occupants of the space to harmful radiation.