The airflow visualization with fog showed that the
cooled ceiling area above axis 3 forced the rising room Ž .
air to recirculate to the occupied zone by convective heat
exchange at the ceiling’s surface. This was causing more
uniform air temperatures on the one hand and higher
contaminant removal efficiencies at axis 3 on the other
hand compare Fig. 8 . The cooled part of the ceiling Ž .
Ž . cooling area 2 appeared to be not as permeable for the
rising room air as the passive part. As a result, the biggest
part of the exhaust air passed the uncooled ceiling area to
leave the test chamber Fig. 10 .