Horizontal illuminance in the office A recorded from 9 a.m. to
8 p.m. was over 500 lx. Horizontal illuminance in the office B was
lower than the illuminance levels in other investigated offices. An
illuminance of 500 lx was exceeded only 3 h from 3 p.m. to 5 p.m.
in the office B. Horizontal illuminance in the office C fluctuated
from 453 lx at 9 a.m. to 488 lx at 12 p.m. On the other hand, the
illuminance in the office D showed the regular patterns, i.e. an
illuminance of 464 lx reached at 9 a.m. and remained almost constant
until 6 p.m. This corresponds to the normal working hours of
administrative staff in the office D.