A method for assessing the performance of nanofiber films coated on window screens in reducing residential exposures to PM2.5 of outdoor origin in Beijing.

Recently, many nanofiber films have been developed for air filtration applications. These films exhibit high PM2.5 (particles with aerodynamic diameters less than 2.5 μm) removal efficiency and relatively low air resistance. Thus, coating window screens with nanofiber films may be able to mitigate residential exposure to PM2.5 of outdoor origin. This study developed a method for assessing the performance of nanofiber window screens in reducing residential exposure to PM2.5 of outdoor origin in Beijing. The results show that the use of selected nanofiber window screens all the time throughout the year can reduce the mean value of the annual average indoor PM2.5 of outdoor origin by 64%-66% for Beijing residences. However, the mean value of annual harmonic average air exchange rate when the windows are open was also reduced from 2.34 h-1 to 0.27-0.35 h-1 , which is far below the national standard. If the nanofiber window screens were used only when the outdoor PM2.5 pollution was severe, the screens had less of an impact on residential natural ventilation, but the national standard still could not be met. Hence, more efforts are needed to further reduce the air resistance of nanofiber window screens in order to ensure proper residential ventilation.