32 ℃ is defined as the initial high-temperature condition. While the adverse effects of this temperature alone on the human body are relatively limited, the addition of thermal radiation may lead to significant negative impacts. However, there is a notable lack of relevant research specifically addressing this temperature condition. This study conducted climate chamber simulation experiments with three designed conditions: 26 ℃, 32 ℃, and 32 ℃ with an additional 2 kW/m² thermal radiation source. During the experiments, subjects remained seated 1.5 meters from the radiation source, resulting in a measured irradiance of 195 W/m² on the frontal body surface. Over a 135-minute exposure period, physiological parameters and subjective sensations were evaluated for 36 subjects, and cognitive performance was assessed using ten different tests. Compared to the 26 ℃ condition, exposure to 32 ℃ alone had a limited impact on physiological parameters, subjective sensation, and cognitive performance. However, with an added 2 kW/m² thermal radiation source at 32 ℃, the core temperature, skin temperature, heart rate, the low-frequency to high-frequency ratio (LF/HF), and weight loss increased significantly. Thermal discomfort and thermal unacceptability also rose markedly, and acute symptoms related to neurobehavioral function intensified. Notably, performance declined significantly in a greater number of cognitive tests, including the stroop test, Tsai-Partington (TP) test, 1-back test, and both high/low load tests. These results indicated that the addition of thermal radiation at 32 ℃ elevated occupational safety risks. This study provides a theoretical basis for establishing new safety standards for work conducted under combined high-temperature and thermal radiation conditions.

Experimental evidence suggests that high temperatures affect cognitive performance; however, there are limited quantitative models available to evaluate or predict this effect. In previous studies, the authors proposed a thermal stress comprehensive index (TSCI), which reflects the coupling of physiological and psychological parameters. Based on this, a comprehensive model of thermal stress and cognitive performance (TSCI-CP model) under high-temperature conditions was established, and its rationality for moderate activity intensity tasks was verified. The present study further investigated the applicability of the TSCI-CP model for low activity intensity tasks. By integrating experimental data from a series of climate chamber experiments conducted at five temperatures (26, 30, 33, 37, and 39 ℃) and two humidity levels (50% and 70%), the relationship between physiological and psychological parameters and the cognitive performance of 104 subjects at a low-activity level (sitting) was analyzed. Subsequently, the TSCI-CP model for low activity intensity tasks was established. The results of the goodness of fit and deviation analysis confirmed the validity of the model. Based on the TSCI-CP model, a new perspective on the relationship between thermal stress and cognitive performance under high-temperature conditions was proposed: the speed of cognitive tests exhibited a U-shaped trend, while the accuracy followed an inverted U-shaped trend. This study offers a theoretical foundation for ensuring the safety and security of low activity workers in high-temperature environments.