Factors affecting lighting fixture operating temperature, fixture life and subsequent suitability for classified areas

A history of the development of early explosionproof incandescent and mercury-vapor lamps and integrally ballasted fixtures is given. The classification of areas in petroleum refineries and chemical facilities, which may be exposed to flammable gases, vapors, or dusts, is discussed, and test methods are briefly described. Problems that arose with the advent of coal gasification and new plastic processes, in which simultaneous exposure to hazardous gases and combustible dusts occurred, are examined. Further process in fixture design, resulting in enclosed and gasketed fixtures suitable for a much broader range of hazardous gases, vapors, and dust and for higher ambient temperatures, is summarized. It is emphasized that today´s engineer must be familiar with all the variables which affect industrial lighting fixtures´ operating temperature and fixture life in order to specify fixtures which will be safe and reliable in process industry environments. Recommendations on assuring maximum safety and reliability are presented