Characteristics of Indoor Environmental Conditions and Air Quality in Selected Schools in Northern Gyeonggi Province, South Korea: Comparisons by Space Type and School Level

Background: Indoor environmental conditions and air quality in schools can vary by classroom type and school level, but comparative assessments remain limited.Objectives: This study evaluated indoor environmental conditions and air quality in selected schools in northern Gyeonggi Province, South Korea, focusing on differences by classroom type and school level.Methods: A cross-sectional survey was conducted at 26 schools (15 elementary, six middle, and five high schools) from March 23 to April 9, 2026.Physical environmental parameters, particulate matter (PM 10 and PM 2.5 ), carbon dioxide (CO 2 ), total airborne bacteria (TBC), formaldehyde (HCHO), and volatile organic compounds (VOCs) were measured.Classroom-type and school-level differences were assessed using the Wilcoxon signed-rank and Kruskal-Wallis tests, respectively.Results: Significant differences between general and special-purpose classrooms were observed for noise, PM 10 , and HCHO (p<0.05).Illuminance also differed significantly between classroom types, although the differences in mean values were less than 1%, indicating limited practical magnitude.Mean HCHO concentrations were 7.36 µg/m 3 in general classrooms and 13.58 µg/m 3 in special-purpose classrooms, representing a 1.85-fold difference.The mean TVOC concentration was 130.82 µg/m 3 in the surveyed special-purpose classrooms.School-level differences were significant only for illuminance in special-purpose classrooms (p<0.05).Conclusions: Significant classroom-type differences were observed for selected indoor environmental and air quality parameters, whereas school-level differences were limited.These findings suggest that indoor environmental assessments of schools should consider classroom type and pollutant concentration distributions in addition to compliance with guideline values.