Vehicle unloading in semi-open industrial buildings frequently release fugitive pollutants, creating significant environmental exposure risks. Current studies have mainly focused on pollutant containment by local exhaust ventilation, while a comprehensive multi-parameter assessment for air curtain performance in semi-open industrial buildings remain undeveloped. This study aims to systematically investigate and optimize the controlling performance of an air curtain for this issue using computational fluid dynamics (CFD) and response surface methodology (RSM). To validate CFD results, simulated results are compared with wind tunnel experimental results. Meanwhile, 51 test cases are conducted to comprehensively explore the interplay among the bottom opening ratio, natural wind direction, and air curtain’s key parameters (jet velocity, angle, and installation type). Results reveal that bottom opening ratio significantly affects pollutant escape, revealing the 30% ratio representing the worst-case scenario. The control efficiency is also sensitive to different natural wind directions. Furthermore, a predictive model with errors under 5% is proposed by RSM, achieving an R² value of 0.96. This model successfully predicts control efficiency for various parameter combinations and provides the optimal operational parameters for three installation types of the air curtain, predicting a peak control efficiency of 98.33% with a top installation at a dimensionless jet velocity of 3.50 and a jet angle of 4.03°. This work provides a theoretical reference for the practical design and operation of air curtains.

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.

During the pandemic, face masks are one of the most significant self-protection necessities, but they also cause heat stress. By using the ERA5 (ECMWF Reanalysis 5th Generation) database and the local weather bureau data, the effect of mask wearing on outdoor thermal sensation has been investigated by a survey conducted in the hot summer and cold winter region of eastern China in the summer of 2020. Results show that wearing a face mask for a longer period result in a higher level of discomfort, and the primary source of discomfort is hot and stuffy feelings. The effect of relative humidity is crucial for mask wearers in warm-biased thermal environments, as mean thermal sensation vote (TSV) peaks when environmental relative humidity reaches the range of 70% to 80% and decreases after this range due to the evaporation within the microclimate created by a face mask. Meanwhile, prolonged mask wearing increases participants' hot feelings, especially in warm environments. Specifically, participants wearing face masks for less than 30 min feel hot at a physiological equivalent temperature (PET) value of 34.4 ℃, but those who wear them for over 60 min express hot feelings even at a PET value of 24.7 ℃. The participants who wear a face mask while walking slowly outdoors have similar thermal sensations to those who do not wear a mask, but are in a higher activity level. The findings demonstrate that mask wearing has a crucial impact on outdoor thermal comfort assessment in a warm-biased outdoor thermal environment.