Table 1 Typology of classrooms in which the measurements were performed; all classrooms could be aired by windows/garden doors that could be opened manually by pupils and/or teachers (MW ¼ classrooms with manually operable windows only, AW ¼ classrooms with automatically operable windows w/o exhaust fan, AW/EF ¼ classrooms with automatically operable windows with exhaust fan, MV ¼ classrooms with mechanical ventilation system).