2024 Yes Indoor Air Quality at an Urban Primary School in Madrid (Spain): Influence of Surrounding Environment and Occupancy https://doi.org/10.3390/ijerph21101263 Alonso-Blanco, Elisabeth Europe Observational Experimental Students Elementary (K-5) Particulate Matter (PM) Black carbon Indoor air quality indoor/outdoor ratio primary school Black carbon ultrafine particle number concentration particulate matter Indoor and outdoor air quality measurements at a Madrid primary school assessed particulate matter, ultrafine particles, and black carbon. Traffic and indoor activity influenced IAQ, supporting targeted strategies to protect children’s health. 2024