Abstract: This paper presents the results of measurements the suspended particles of the PM10 and PM2.5 fractions in two high schools in Bor (School of Mechanical and Electrical Engineering - MS and Grammar School - GM). The measurements were conducted in two heating seasons for a duration of seven days (five weekdays, and two weekend days). Periods during the weekdays when there were classes and weekend days when there were no classes at school were analyzed separately. The measurement results show that the average concentrations of suspended particles PM10 during the class period were 1.7 (GM) and 2.4 (MS) times higher than in the period without classes. The average concentrations of suspended particles PM2.5 in both schools during the class period were 1.5 times higher than in the period without classes. In MS the average PM10 and PM2.5 concentrations during classes were above daily limit values for 3 of 5 working days. In contrast, there was no exceeding of the average daily limit values for concentrations of suspended particles during classes in GM. The results of measurements indicate that more attention should be paid to the way classrooms are cleaned to reduce the possibility of particles resuspension due to the movement of pupils during the teaching period. Tasić, Viša Kamenović, Vladan Urošević, Tamara Radović, Bojan Apostolovski-Trujić, Tatjana Damjanović, Zvonko https://unilib.phaidrabg.rs/o:5929 doi:10.5937/mmeb2302047T cobiss:136801289 ISSN: 2406-1395 info:eu-repo/semantics/article Suspended particles concentrations in the secondary schools in Bor (Serbia) in heating season 2023 Keywords: classroom, real-time monitoring, particulate matter, air pollution. eng http://creativecommons.org/licenses/by/4.0/legalcode Mining and Metallurgy Engineering Bor number: 2 startpage: 47 endpage: 54 application/pdf 1499272 bytes