Non-visual effects of lighting characteristics on workers in industrial workplaces.

While the impact of lighting environment on comfort has been thoroughly investigated, its impact on human physiology and behaviors is yet to be fully understood. Since the recent discovery of the new class of photoreceptors in the mammalian retina, it has become evident that light is crucial for controlling non-image formation (NIF) processes like circadian rhythms, alertness, well-being, and mood, all of which have an impact on a user's overall comfort. This can be crucial for the indoor working environment, considering also the category of industrial workers which is overlooked in scientific research despite its importance to ensure improved performance and productivity. Therefore, this paper aims to understand the effect of lighting characteristics, duration of exposure to lighting, and timing on the non-visual functions of workers in industrial workplaces. A field study was conducted in three industrial buildings to measure lighting characteristics in winter and summer during different time intervals. Simultaneously, the workers' self-evaluations of five non-visual functions, namely comfort, mood, alertness and satisfaction, were recorded and statistically analyzed. The results also revealed evident effects of both horizontal and vertical lighting, as well as color temperature, on the comfort, mood, and subjective alertness of workers.