Exploring the effects of mask wearing on outdoor thermal comfort at different walking speeds—A thermal manikin-based experiment

Face masks’ wearing for a long duration brings thermal discomfort, especially in hot climate cities. The face masks’ thermal insulation and its effect on outdoor thermal comfort have been rarely investigated. In this study, five types of face masks and their thermal insulations have been tested by using a thermal manikin in the climate chamber. Experimental results are assessed by using physiological equivalent temperature (PET) and standard effective temperature (SET*) for thermal comfort with masks at three walking speeds both in summer and winter. Slight differences in thermal insulation are observed among the different masks, the values of PET and SET* rise with increasing mask thermal insulation, and they are generally higher in summer than in winter. Moreover, the variation of SET* is more obvious than PET with same masks at different walking speeds. And the differences of SET* with and without masks appear to rise significantly for fast walking. Results further indicate that the individuals’ physical discomfort caused by wearing masks cannot simply be assumed as an additional effect of the clothing thermal insulation. The findings enrich the clothing thermal insulation database, explore the differences in thermal indices if the face mask is used, and provide advice on heat mitigation with masks outdoors.