Since exhaust 2 was closer to the contaminant sources, it could
extract more contaminants such as a local exhaust hood, which was
very beneficial. This would also require the exhaust be very close to
the contaminant sources. When the spill was at location 3 which
was a bit further away from the exhausts, the two exhausts had no
impact on the contaminant concentration in the laboratory, as
illustrated in Fig. 7(c).