light intensity and ultraviolet radiation in the libraries and computer sites of ilam universities

background: light is an important and adjustable physical factor in the job environment.this study aimed to determine the intensity of natural and mixed light and also the level of ultraviolet radiation in libraries and computer sites of ilam universities in spring 2011.   methods: in this cross-sectional study, 10 libraries, 16 study saloons, and 7 computer sites were selected. luminosity assessing form was used to collect related data about selected places. light intensity measuring device (hanger-ec 1 ) and ultraviolet radiation­ intensity measuring device (hanger- ec 1 ) were used to measure these two variables. measurement was performed according to the suggested method by iesna and data analysis was done by spss17 software.   results: mean general light intensity of libraries in mixed and natural conditions, were respectively 235.2±140.2 lux and 198.2±154.6 lux. maximum mean of ultraviolet radiation in mixed and natural conditions were 0.012±0.0131 and 0.008±0.007 w/m 2 respectively. these show that light intensity and ultraviolet radiation in the majority of studied units were significantly higher in mixed conditions (natural and artificial light) than in the natural conditions.   conclusion: improper design and light source selection, oldness of the constructions, and altering the applications of the constructions from administrative places into libraries, studying saloons, and computer sites have caused light intensity lower than the standard levels in these places. therefore, redesigning the light systems is necessary.