In nursery N_URB2, LR showed the highest PMconcentrations for
the finer fractions (PM1 and PM2.5) during the occupancy period and
during the dawn and morning. Cooking activities are also one of the
major indoor sources of PM (Monn, 2001) and might explain the
higher concentrations observed as these activities started very early
in the morning (8 h) and ended late at the afternoon (19 h). In this
nursery it was also possible to observe that classroom C had the
maximum PM concentrations (peaks) in all fractions, but especially
higher for PMTotal, which can be attributed to three major synergetic
factors: i) a higher occupancy in this classroomwhen compared with
others in this nursery with similar areas (Table 1); ii) poor ventilation
(doors to outdoor were always closed and to the inner corridor were
almost always closed); and iii) normal activities characteristic of 4
years old children (occupants of this classroom). Also in classrooms C
and B in this nursery, itwas possible to observe the three peaks in the
concentrations on weekdays, also in the three main occupancy periods
(morning and afternoon before and after the break), and for the
same reasons than in N_URB1. On the other hand, classroomA (baby
nursery) showed a different pattern, with the highest concentrations
being registered between 13 and 15 h. Thiswas the period of sleeping
for the babies in the cribs room (next to and opened to classroom A)
and teachers took the chance to do some tidying. On weekends, PM
concentrations were lower and the profiles were similar and almost
constant for the two measured classrooms (A and C).