Study On The Thermal Comfort Of Pedestrians Wearing Masks In Semi-open Spaces In Guangzhou

Since the 2019 coronavirus disease(COVID-19)outbreak,wearing a mask has been advocated as an effective way to prevent the spread of coronaviruses.Although the outbreak has stabilized,the coronavirus has not been eradicated and people still need to wear masks indoors and outdoors for prevention.Nowadays,people are at a lower risk of infection and tend to be active outdoors.As a common outdoor activity,walking increases a person’s activity level,which leads to an increase in the body’s metabolic rate,and changes in metabolic rate can affect thermal sensation.Moreover,wearing a mask affects the exchange of heat and humidity between the body and the environment,which in turn affects the body’s thermal comfort.Wearing a mask can cause discomfort,leading people to wear it unscientifically and irregularly,which can seriously affect their healthy lives.There are few studies on the effects of wearing masks on human thermal comfort and thermal safety,so there is a need to investigate the effects of wearing masks on human thermal comfort during outdoor activities.From October to December 2020,the authors conducted a study on the measurement of environmental parameters and thermal comfort questionnaires in the outdoor area of Guangzhou University,collecting 1160 valid questionnaires;then from March to April 2022 and from June to July 2022,the author conducted simulated experiments in a semi-open space of a teaching building,recruiting 30 and 28 subjects respectively,each wearing different types of masks(no mask,medical mask and KN95 mask)and walking at three speeds at a constant speed,during which environmental parameters and human physiological parameters were measured in real time and subjective thermal evaluations of the subjects were collected,collecting a total of 7128 valid questionnaires.Firstly,this paper preliminarily examined the impact of mask-wearing on outdoor pedestrians’ thermal comfort and the adaptability of physiological equivalent temperature(PET)to pedestrians wearing masks in semi-open spaces.The results of the study indicate that wearing masks can improve the thermal sensation of the human body,especially the thermal sensation of the face.Pedestrians wearing masks require lower temperatures to feel comfortable and expect cooler environments.PET was utilized to predict the thermal sensation of masked pedestrians in semi-open spaces.Secondly,the researchers conducted a statistical analysis of the changes in subjects’ subjective sensory voting and physiological indicators and analyzed the effects of walking speed and different types of masks on human thermal sensation.The results suggest that wearing a mask can shift the thermal sensation vote of the subjects toward the hot end(TSV=1～3)and this effect is more pronounced for the thermal sensation of the face.Wearing masks in the spring can improve human thermal sensation more than in the summer,and the impact of wearing masks on facial thermal sensation is stronger than the overall thermal sensation.Compared to the non-mask group,the overall thermal sensation and heart rate of the mask group took longer to return to the sedentary state after walking.The maximum acceptable walking speed in a semi-open space was 1.63m/s in spring when wearing medical masks,1.38m/s in summer when wearing medical masks,and 1.09m/s when wearing KN95 masks.Lastly,the researchers calculated and corrected the neutral values of PET and the universal thermal climate index(UTCI)under different working conditions,and modified the thermal grade intervals of PET and UTCI by considering psychological and physiological influences comprehensively.At the same time,this study was compared and discussed with other outdoor thermal comfort studies.The results showed that in spring,PET underestimated the cold tolerance of pedestrians in semi-open spaces,while UTCI overestimated it;In summer,PET overestimates the thermal sensation of pedestrians in semi-open spaces,while wearing masks improves the thermal sensation,which is closer to the original PET scale.The original UTCI scale underestimates the thermal resistance of pedestrians in semi-open spaces.In conclusion,the study integrated the thermal environment,human psychological response and physiological response to analyse the effect of wearing a mask on pedestrian thermal comfort in semi-open spaces in the Guangzhou area.Ultimately,the study revealed the changing pattern of thermal comfort of pedestrians wearing different types of masks in semi-open spaces,clarifies the degree of influence of mask type on thermal sensation,and then modifies the PET and UTCI evaluation indicators so that they can more accurately evaluate the thermal comfort of pedestrians wearing masks outdoors.On the basis of comfort requirements,the study identified reference walking speeds,which provide a scientific basis for healthy walking with pedestrians wearing masks.