The sense of sight is the most important human sense by which the maximum information may be obtained from the surrounding environment. Therefore, there should be adequate light. Thus the present study evaluates the illumination intensity of one of the bolt manufacturing industries to use its results for corrective measures. This study is a cross - sectional study that is conducted in one of the bolt manufacturing industries in Yazd City. Measurement of natural and artificial light is done in 2014 in a cloudy day in December by network method in manufacturing, molding, threading and pulling facilities by lux meter model TES 1330A. Then using this information the illumination map of the isolux of the manufacturing hall is mapped by ArcView software. Since most working hours of workers is associated with systems in fixed points, the local illumination in the operation area is measured. The highest measured points is associated with manufacturing hall (54 points) and the least points is associated with the molding hall the (14 points). The results showed that the minimum and maximum combined illumination intensities are associated with molding (153.92 ± 106.91) and manufacturing (88.39 ± 325.11) halls. Natural illumination level is calculated in terms of the halls that the minimum illumination is associated with molding hall (114.33 ± 80.50) and the maximum illumination is associated with manufacturing hall(66.25 ± 253.12). In manufacturing hall most points are in the range of above 300L. The percent of light bulbs in the manufacturing halls is 70%. Some bolt manufacturing halls had good combined illumination but they lacked proper natural illumination. Thus by necessary interventions such as replacement of the broken lamps, correct alignment and cleaning the lamps it is possible to achieve an optimal level of illumination.
