Experimental investigation of the effect of surgical masks on outdoor thermal comfort in Xiamen, China.

The COVID-19 pandemic has significantly changed people's lifestyles, and wearing surgical masks in outdoor public spaces has become commonplace. However, few studies have explored the impact of wearing masks on outdoor thermal comfort in different seasons. From May 2021 to February 2022, a series of longitudinal experiments were conducted in Xiamen, China to examine the effect of wearing surgical masks on outdoor thermal comfort. Forty-two participants took part in the experiments with and without masks. During the experiments, the thermal perceptions of the subjects and environmental thermal parameters were collected. Differences in outdoor thermal comfort between subjects wearing masks and those not wearing masks were determined in summer, autumn, and winter. Results showed that 1) the subjects wearing masks had lower neutral temperatures, and this difference was particularly pronounced in summer and exacerbated by walking; 2) in warm environments, masks reduced thermal comfort, and discomfort associated with masks was worse when walking than when sitting; 3) wearing masks significantly worsened facial comfort and increased chest discomfort, as summer turned to winter, the impact of masks on facial comfort decreased; 4) radiation and air temperature were the environmental parameters with the greatest impact on outdoor thermal sensation. Subjects who wore masks preferred lower temperatures, radiation, and humidity, and higher wind speeds.