Effects of the Corona Pandemic on Indoor Fine Dust in Urban Schools

Corona pandemic restricted industrial activity of the country, influenced social activities of people, and changed students' school programs. PM10 and PM2.5 measured in National Air Quality Monitoring Systems were reduced from 36.1 μg/m 3 to 34.5 μg/m 3 , and from 20.3 μg/m 3 to 18.5 μg/m 3 , respectively. In particular, obvious decrease of indoor PM2.5 with high dependency on outdoor air quality was estimated. As a result of precise field tests in 179 classrooms of 53 schools, indoor PM2.5 showed a low average, 23 μg/m 3 , and PM10 also was lower 33 μg/m 3 than before and after the pandemic (51 μg/m 3 and 59 μg/m 3 respectively). Due to a variety of class work, limited attendance, air purifier operation and frequent window opening, it was not easy to drive a consistent impact of the Corona pandemic at the indoor PM level. Consequently, the indoor and outdoor airborne fine dust concentrations became more similar than normal conditions, and indoor emission amount of PM10 in particular decreased.