Investigation on a new semiconductor cooling garment for reducing heat stress of outdoor workers performing moderate activities in a hot and humid environment

The incidence of heat waves increases frequently over the last decades in China and the worldwide, which will be more frequent, persistent, and intense with global warming and rapid urbanization. Outdoor workers, as the most influenced groups, die every year due to the severe heat illnesses associated with the thermal environments. Though various personal cooling garments (PCGs) have been developed to reduce the heat stress of human body working in extremely thermal environments or in indoors, less research studies were performed for developing PCGs for outdoor workers. Besides, there still lacks study for developing PCGs with good portability, large, prolonged and steady cooling effect. Therefore, in this study, a newly developed semiconductor cooling clothing was developed based on semiconductor units (SCG), and its actual cooling performance was evaluated by having ten males performing a moderate activity in a hot and humid condition (i.e., 30 ± 0.5 °C, RH = 80 ± 5 %, partial water vapor pressure = 3.5 kPa). The total experimental duration was 60 min, consisting of 60-min walking at 5.0 km/h. The key findings showed that the SCG could significantly reduce the mean skin temperature, torso skin temperature as well as local skin temperatures of human body under moderate exercise intensities (p < 0.05). Perceptual sensations in the whole-, upper-, and lower- body were remarkably improved during exercise (p < 0.05). In addition, the cooling performance of SCG was still significant approaching the end of the trials. Besides, no body movement restriction was discovered for subjects in SCG while performing typical postures. It was thus concluded that the SCG is effective in alleviating body heat strain while exercising in a hot and humid environment. The findings contribute to the body of knowledge in improving the health and well-being of outdoor workers while working in hot and humid environments.