Temporal psychological and physiological responses to 120-hour isolation in an underground rescue chamber: A preliminary study

The development of underground space has become a strategic focus in both infrastructure engineering and urban sustainability planning, drawing increasing attention to human health. While prior studies have primarily examined the health effects of routine exposure to controlled urban underground environments, their findings cannot be directly applied to emergency rescue chambers. Existing research on rescue chambers has been limited to no longer than 48-hour exposures, with a few thermal studies extending to 106 h but lacking analyses of psychological and physiological responses. Moreover, the moderating effects of individual characteristics have not been well understood. To address this gap, this study conducted a 120-hour simulated experiment with eight male participants to investigate how exposure duration interacts with individual characteristics to influence human psychological and physiological responses. The sample size was constrained by the rated capacity of the rescue chamber, and multiple runs were not allowed for this exploratory study due to participant health and safety concerns. The results showed that positive emotion and team relationship deteriorated over time, with a faster decline for participants with higher openness and mental health. Furthermore, positive emotion mediated team relationship changes, highlighting the critical role of affective states in maintaining interpersonal cohesion. Notably, participants with better mental health experienced more stable interpersonal dynamics, even in the face of emotional fluctuations. While no significant changes were observed in heart rate, heart rate variability, and breathing rate, some correlations were detected between physiological and psychological measures. Overall, these findings contribute to empirical evidence on human adaptation to confined underground environments and offer practical implications for rescue chamber design (e.g., increasing space and incorporating privacy features to sustain positive emotion and preserve team cohesion) and personnel training (e.g., developing psychological resilience, teamwork skills, and stress management strategies to prepare workers for prolonged confinement). However, the findings should be considered exploratory findings due to the small sample size. Future research with larger and more diverse samples in ecologically valid settings is warranted to further validate these findings.