However, the
results of statistical comparison indicated that there were no significant
differences between the exposure levels to total respirable
quartz dust (p = 0.144 > 0.05), which suggested that the use of Dust-
Bubble could not significantly reduce the quartz exposure level of
workers when drilling concrete. Moreover, both the GM of quartz
concentration values of two groups (0.07 mg/m3 and 0.04 mg/m3
respectively) were over or close to the exposure limit, which suggested
the concrete drilling process can generate high level of
quartz dust and DustBubble is inadequate to protect workers. Other
dust control measures (e.g. wet methods, and LEV) should be taken
to reduce the quartz exposure level to below the limit. The workers
should also wear appropriate respirators.
The workers using DustBubble were also interviewed to collect
their feedbacks on the use of DustBubbles. They suggested that
the use of DustBubble could reduce the dust generated for there
was less settled dust or visible dust during the drilling with
DustBubble (as shown in Fig. 6). However, it was commented that
it is not so convenient to use DustBubble for there are several steps
to prepare before the drilling. It was also claimed by the workers
that it would take far much more time (normally two or three times
longer than the normal duration) to finish drilling a hole, which may
stop the contractors from using DustBubble. Sometimes, the
DustBubble could not stick to the slab firmly during the drilling
and dust was leaked out in that case.