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
concentrations during occupancy, most probably due to the lower
occupancy on this classroom (only 7 people) when comparing to
the others. The lower concentrations observed in the LR on this
nursery were possibly due to its size and the existence of a small
hall that creates a discontinuity between the kitchen and the lunch
room, which possibly diminishes kitchen PM penetration into the
lunch room. On weekends the concentrations were lower than on
weekdays, and the behaviour for the different rooms was similar,
with the exception of classroom C where they were higher on the
first hours of the day. As this was clearly the room with the highest
concentrations during weekdays, thiswas the result of the decrease
of PM concentrations in the beginning of the weekend (Saturday
dawn) e settlement phenomenon.