Field Tests of Indoor Air Cleaners for Removal of PM2.5 and PM10 in Elementary School Classrooms in Seoul, Korea

Control of fine particles in childcare centers, elementary schools, elderly care facilities and other locations where vulnerable people spend most of their time is essential. This study investigated PM 2.5 and PM 10 concentrations in two classrooms equipped with one and two air cleaners, respectively, compared with concentrations outdoors and in a classroom with no air cleaner. Eight models of air cleaners with clean air delivery rates ranging from 9.9 to 21.3 m 3 min –1 were tested in the classrooms of two elementary schools in Seoul. Average PM 2.5 and PM 10 levels were 7.3 ± 0.7 and 45.5 ± 4.1 µ g m –3 in classrooms equipped with one air cleaner and 4.2 ± 0.6 and 24.6 ± 2.5 µ g m –3 in classrooms with two air cleaners, whereas they were 22.1 ± 2.6 and 109.1 ± 9.6 µ g m –3 in classrooms with no air cleaner and 36.9 ± 5.1 and 74.1 ± 10.6 µ g m –3 outdoors, respectively. The PM 2.5 level in classrooms was effectively reduced by one or two air cleaners because PM 2.5 infiltrated mainly from outdoors; meanwhile, PM 10 could not be reduced as PM 10 originated mainly from indoors from student activities. Air cleaners were more effective at removing PM 2.5 and PM 10 in classrooms with high airtightness than in classrooms with low airtightness. The average CO 2 concentration in classrooms was approximately 1500–2000 ppm during class hours and depended on the number of students per classroom; this level was approximately 1.5–2 times higher than the standard, regardless of the use of air cleaners.