and most times aboveMean I/O ratios

and most times above


Mean I/O ratios were always above 1 and most times above 2 showing that
indoor sources (re-suspension phenomena due to children’s activities, cleaning and cooking) were
clearly the main contributors to indoor PM concentrations when compared with the outdoor influence.
Though, poor ventilation to outdoors in classrooms affected indoor air quality by increasing the PM
accumulation. So, enhancing air renovation rate and performing cleaning activities after the occupancy
period could be good practices to reduce PM indoor air concentrations in nurseries and, consequently, to
improve children’s health and welfare.