Ventilation strategies of school classrooms against cross-infection of COVID-19: A review

Under current pandemic of COVID-19, children are still spending long hours in school classrooms every day. A literature study is therefore conducted to investigate the current ventilation strategies used in schools and assess their performance of controlling contagious respiratory diseases in the indoor environment, and also to seek for future solutions. Research papers, reports and standards relevant to school ventilation, airborne transmission and complementary air distribution methods are reviewed. It is concluded that schools usually have natural ventilation (NV) or mechanical ventilation (MV), however the overall indoor air quality is not ideal. Both NV and MV can reduce the airborne transmission of respiratory droplets efficiently when designed, operated, and maintained properly, yet schools are in shortage of informative standards and guidance. Personalized ventilation (PV) has a promising potential in protecting occupants from local indoor air contaminants, yet further studies are needed before PV can be applied to children in classrooms.