PM concentrations were often found high in the studied classrooms,
mainly in the finer fractions (PM1 and PM2.5), and often
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.