Physiological and subjective responses across mask-wearing in a summer air-conditioned environment

This study investigated the thermal comfort effects of surgical and N95 masks in a summer air-conditioned environment (23.0–28.0°C) using a three-stage experimental design with 24 sedentary subjects. Physiological and subjective responses were measured during adaptation (Stage I), mask-wearing (Stage II) and post-removal (Stage III). Results showed that mask-wearing could significantly increase facial skin temperature in Stage II, leading to warm and humid discomfort, whereas facial thermal conditions recovered rapidly after mask removal and in slightly warm environments (28.0°C), comfort levels exceeded those in the adaptation stage, indicating thermal adaptation. Core temperature and heart rate remained stable throughout, confirming that mask-related discomfort was primarily localized. Compared with surgical masks, N95 masks consistently resulted in lower thermal acceptability, with differences of up to 9.0%. Thermal analysis revealed that the overall neutral temperature increased from Stage I to Stage III, while the preferred temperature remained consistently lower than the neutral temperature. During mask-wearing, the acceptable facial temperature range shifted towards cooler conditions and expanded after mask removal, indicating enhanced thermal tolerance. Based on these findings, a facial thermal comfort prediction model was developed using nasal and chin skin temperatures, providing quantitative support for thermal comfort management and mask selection in summer air-conditioned environments.