Abstract: A heat retaining sleeve for raising the cold spot temperature of a fluorescent lamp is comprised of a base end, a distal end, and a sleeve body sized and shaped to fit over the end of a fluorescent lamp or lamps where the lamp's cold spot exists. The sleeve creates a heat retaining air gap between the inner surface of the sleeve body and the lamp end or ends with the cold spot, and has sufficient length to so that, when fitted over the lamp end or ends, the cold spot temperature is elevated to a temperature that increase the lumen output of the fitted fluorescent lamp or lamps.

Abstract: A diffuser element for a source of light is comprised of a body having an observable portion fabricated of a light diffusing material. The observable portion of the body has a light incident surface and a light exiting surface opposed to the light incident surface, each of which has a contoured surface pattern. The contours for the opposing contoured surface patterns are chosen to achieve a desired visual characteristic for the diffuser element including a desired brightness distribution across the contoured surface pattern of the light exiting surface.

Abstract: A method and system for indirectly illuminating an open interior space, such as an open office, includes using individual lighting fixture modules, each comprised of at least one, and preferably a pair of side-by-side parallel linear indirect fluorescent lighting fixture elements suspended at fixed grid pattern locations beneath the ceiling of the open interior space. Each of the linear indirect lighting fixture elements of the fixture module is preferably no greater than approximately six feet in length with a suitable length being somewhat greater than four feet where a four foot lamp is used. Where the fixture elements are provided in pairs, each is suspended below the ceiling at its fixed grid location by a suitable hanger structure that maintains a spacing between the fixture elements that establishes a preferred overall fixture module with of approximately four feet.

Abstract: A tank cartridge is described which is capable of withstanding rough handg during loading and unloading operations.