Dynamic impacts of face masks and walking duration on pedestrian thermal comfort in shaded outdoor environments during summer.

The normalization of mask-wearing in the post-pandemic era has raised concerns regarding its potential thermal burden during outdoor physical activities, especially in hot and humid climates. This study examines the combined effects of face mask type (no mask, surgical mask, and KN95 mask) and walking duration on physiological responses and thermal comfort in shaded outdoor environments during summer. Field experiments were conducted in Guangzhou with 28 participants walking at three speeds (1.2, 1.4, and 1.6 m/s). Key physiological parameters (mean skin temperature, heart rate, tympanic temperature) and subjective thermal comfort votes (respiratory sensation, facial thermal sensation, and overall thermal sensation) were recorded. Findings revealed that mask-wearing had negligible effects on core physiological indicators due to compensatory thermoregulation but significantly elevated subjective discomfort, particularly with KN95 masks. A linear increase in thermal discomfort was observed with prolonged walking, reaching up to 1.3 units in thermal sensation votes after 30 min. A dynamic thermal comfort prediction model was developed by integrating static PET-based and walking-induced components, achieving high predictive accuracy (R² > 0.78). These results underscore the importance of incorporating mask effects and exposure duration into urban outdoor thermal planning and pedestrian design guidelines in hot-humid regions.