2017 No https://www.sciencedirect.com/science/article/abs/pii/S0048969717305533?via%3Dihub Stabile Europe Experimental Elementary (K-5) Ventilation rates Temperature Humidity Particulate Matter (PM) School Exposure Particles Airing strategy Carbon dioxide (CO2) Ultrafine particles Ventilation Results revealed that the airing strategy differently affect several pollutants detected indoors depending on their size, origin and dynamics. Longer airing periods may result in reduced indoor CO2 concentrations and, similarly, other gaseous indoor-generated pollutants. Simultaneously, high ultrafine particle (and other vehicular-related pollutants) levels in indoors were measured due to infiltration from outdoors. Finally, a negligible effect of the manual airing on PM levels in classrooms was detected.