Influencing assessment of mask wearing on thermal comfort and pleasure during outdoor walking in hot summer region

Face masks are normally used by ones who work /walk outdoors to protect them away from air pollutants, for instance, traffic police, but the impact on the outdoor thermal perception is rarely reported in high-density cities during extreme hot summer. This study aims to explore the effect of face mask wearing on subjects' thermal perceptions with walking in Shanghai during summer. 796 valid questionnaires with environmental measurement and physiological parameter are collected respectively under the condition of with and without wearing surgical face masks. Results point out that subjects show higher thermal sensation, exertion, and lower thermal comfort as well as pleasure when they put on face masks, and a negative effect exists on the recovery of subjects' physiological parameters and perceptions after walking. Subjects wearing face masks are more prone to thermal stress, as they feel hot at the physiological equivalent temperature (PET) value of 52.4 °C in no masking condition, but 48.6 °C in masking condition. Meanwhile, subjects respond less thermal comfort in hot outsides with face masks even in slow walking. The research finally proposes an assessing range of thermal perceptions with activities for PET to better understand outdoor thermal comfort in mask wearing conditions during hot summer. •Wearing face masks influences the exertion, thermal comfort, and pleasure.•Recovery process of perceptions after walking is negatively impacted with wearing masks.•Thermal stress is more significant when face masks are worn even walking slowly.•Range of thermal perceptions with mask wearing for PET is given during walking.