Abstract—This study investigates the relationship between indoor and outdoor (Particulate Matter 10) PM10 concentrations in two schools in Barreiro, Portugal: Primary School No. 5 and D. Luís Mendonça Furtado Basic School. The primary objective is to assess the influence of both external and internal sources on Indoor Air Quality (IAQ) in school environments. Monitoring campaigns were conducted across various indoor spaces, including classrooms, the gymnasium, and the canteen, with results compared to outdoor PM10 levels. At Primary School No. 5, indoor PM10 concentrations were consistently higher than outdoor values measured on Avenida do Bocage, with an average Indoor/Outdoor (I/O) ratio of 2.2, highlighting the strong impact of indoor activities on particulate matter levels. Similarly, at D. Luís Mendonça Furtado Basic School, PM10 and PM2.5 concentrations increased significantly during school hours, peaking at an I/O ratio of 3.04 on school days. Conversely, during evenings and weekends, when the spaces were unoccupied, particle concentrations dropped substantially, reaching an I/O ratio of 0.70. These findings underscore the critical role of indoor activities in elevating PM10 levels and emphasize the urgent need for effective ventilation and pollution control strategies in schools to safeguard the health of students and staff.

Keywords—Indoor Air Quality (IAQ), PM concentrations, School air pollution

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Cite: João Garcia and Rita Cerdeira, "Assessing Indoor and Outdoor PM10 Levels in School: Insights from a Case Study," International Journal of Environmental Science and Development vol. 16, no. 3, pp. 226-233, 2025.

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