Study On The PM2.5 Penetration Through Exterior Windows Under Different Conditions And Control Methods

In recent years, hazy weather has occurred frequently in most parts of China which leads to a severe particulate matter pollution. The fine particulate matter (PM2.5) has significant effects on human health. PM2.5 penetration through building envelope is a main approach that ambient PM2.5 enters into indoor environment, and the exterior window is the primary path of PM2.5 penetration in current buildings. The penetration factor is used to assess the penetrability of particulate matter, and it is also a parameter that has a significant impact on particulate matter penetration through building envelope into indoor environment. Various conditions including meteorological conditions, particulate matter diameters, air change rate and the conditions of cracks have great influence on PM2.5 penetration, hence it brings some uncertain effects for indoor PM2.5 control and design. For this reason, this study focus on the regular pattern of PM2.5 penetration through exterior windows and the different characteristics of the penetration factor under different conditions.The behavior of opening windows under the effect of haze weather is investigated by means of questionnaire. It is found through investigation that people have formed a habit of opening windows for natural ventilation. However, this behavior is affected to different degree by hazy weather. Despite people's attitude towards PM2.5 and ambient air quality has the feature of "knowing more while being less concerned", more than 50% of all. respondents will close their windows to barrier penetration of ambient PM2.5 into indoor environment in hazy weather. There is a significant correlation between indoor and outdoor PM2.5 concentrations, and windows with higher air tightness have a stronger PM2.5 barrier ability, which means that windows with higher air tightness can withstand more severe PM2.5 pollution in the condition of same indoor PM2.5 concentration. The concentration that PM2.5 penetrate through exterior windows into indoor environment has close relationship with air infiltration of exterior windows. So based on the conditions of exterior window interstice, window air tightness and air infiltration mechanism as well as combining with the interstice-method theory, the calculation method of air infiltration under different conditions is put forward, and then the concentration model of PM2.5 penetration through exterior window (PM2.5-PC-model) is established.The PM2.5 concentration and the particulate matter diameter distribution of indoor and outdoor environment were measured for a long-term monitoring in Beijing. The results of statistic analysis show that the relative humidity and wind speed influence the particle size distribution as well as the relationship of indoor and outdoor PM2.5 concentrations. According to the results, a PM2.5 penetration performance test platform is established. The study method of PM2.5 penetration through window based on window air tightness is provided and the experiments of PM2.5 penetration through windows are carried out by using of synthetic test dust. The experiments indicate that penetration factors fluctuate within a certain range when the indoor and outdoor conditions keep stability. Overall, the penetration factors of diameter less than 1?m are bigger and the penetration factors of diameter larger than 1?m are relatively smaller; at window with higher air tightness, the penetration factors are smaller. For mass concentrations, under all pressure differences, most of the mean penetration factors of PM0.5 are bigger than 0.90, the mean penetration factors of PM1.0 and PM2.5 are respectively distributed in the ranges of 0.77-0.95 and 0.62-0.85.It is found that the variation characteristics of penetration factor are as follow:with an increase of pressure differences, penetration factors of PM2.5 increase in the condition of window air tightness at level 4, change slightly in the condition of window air tightness at level 5 and level 6, and firstly increase and then decrease. According to the variation characteristics of PM2.5 penetration factor, PM2.5 penetration factor models of different window air tightness levels (PM2.5-PF-model) are established and optimized.The PM2.5 pollution status of typical cities in China are analyzed, and based on the concept of guarantee rate, a determination method of PM2.5 outdoor design concentration is put forward. Combining with PM2.5-PC-model and PM2.5-PF-model, the calculation method of PM2.5 exterior window penetration load is obtained. Furthermore, some passive control measures are carried out, including reasonably improving window air tightness, ensuring the product quality and the installation quality of sealing strips of exterior windows, enhancing the sealing of reserved holes in building walls and maintaining periodically.The results of this study can not only provide a theoretical foundation for indoor PM2.5 concentration prediction and exposure research, but also a control design method and control strategies for indoor PM2.5 pollution, which have theoretical and practical value.