In order to evaluate the impact of windows with different structure characteristics on the building facade' s barrier property of PM2. 5 , a longitudinal monitor regarding PM2. 5 mass concentration and air particle size distribution was conducted in two offices located in Beijing, China. The two offices were equipped with windows with different structure characteristics, and both offices were monitored between July and October, 2014. In this paper, the characteristics of PM2. 5 infiltration of the two types of windows were compared and potential influential factors were identified,and the infiltration pressure △p was proposed and the relation among windows structure characteristics, wind speed and relative humidity was analyzed. The survey results showed that the proportion of outdoor air particles between 0. 7 ~1. 0μm was proportional to the outdoor PM2. 5 mass concentration, while the proportion of particles between 0. 3~0. 5μm was inversely proportional to the outdoor PM2. 5 mass concentration. The barrier property of both window types on particles smaller than 0. 7 μm was low. However, the windows with larger airtightness can show higher barrier property. From the study, the infiltration pressure△p and infiltration factor Fin showed to be affected by outdoor wind velocity and relative humidity. The △p and Fin of sampling site 1 were always lower than that of sampling site 2 .%为了把握不同结构型式建筑外窗对室外PM2.5阻隔特性及其影响规律,基于细颗粒物穿透机理与沉降特性,结合项目组2014年7月到2014年10月关于北京地区临街办公建筑室外及室内环境PM2.5质量浓度水平以及粒径分布特性的实时监测数据分析结果,重点比较分析了建筑外窗关闭且无室内源条件下,不同结构型式建筑外窗室外PM2.5渗透特性及其变化规律,并给出了建筑外窗缝隙通风条件下,缝隙渗透通风作用压力△p与建筑外窗缝隙结构特征、室外风速、室外空气相对湿度的关联式.研究结果表明：大气环境中粒径>1.0μm的颗粒物不到10%,且粒径<1.0μm的细颗粒物粒径分布随室外PM2.5质量浓度的增加呈向较大粒径0.7~1.0μm转化趋势,反之呈向较小粒径0.3~0.5μm转化趋势；2个不同结构特性建筑外窗对粒径<0.5μm细颗粒物的阻隔作用非常有限,对粒径>0.5μm,特别是0.7~1.0μm粒径细颗粒物的阻隔作用明显增加；建筑外窗渗透通风作用压力△p、渗透系数Fin与室外风速呈正相关性、与室外空气相对湿度呈负相关性；更高气密性等级建筑外窗对室外PM2.5侵入室内的阻隔性能始终优于低气密性等级建筑外窗.
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