In nursery N_URB1, classroom C had the highest PM concentrations
which could have been the result of the cumulative effect
of three major conditions: i) poor ventilation (there were no open
direct access to the outdoor and the door to the inner corridor was
almost always closed); ii) high occupancy, with a total of 25 persons,
despites being the room with the higher volume; and iii)
intense activity, characteristic of 5 years old children. Additionally,
it was possible to notice three peaks in the PM profiles for all the
studied classrooms, which represented the three main occupancy
periods (morning and afternoon before and after the break). In
nursery N_URB1, classroom B revealed the lower PM