The brush/bowl method successfully collected dry dust samples
from the roof in all of the mines. It was able to easily and safely
capture dust in high-roof mines and from the roof areas above
conveyor belts. The brush/pan method still worked well when
collecting rib samples. When mesh was installed on the ribs, the
PVC scoop provided an alternative method to collect dust from the
rib surface behind the mesh as well as the dust deposited on the
mesh. The brush/pan method was the easiest to use when collecting
dust samples from the floor but a light hand is required to
obtain only the top 3 mm of dust. It was easier to collect the top
3 mm of floor dust with the cheese planer. However, larger bits of
coal or rock can interfere with the dust collection. The plug sampler
worked well to take samples of less than 1 mm. However, in order
to obtain sufficient dust for analysis, several “plugs” were needed
and the sampling became much more time consuming. As with the
cheese planer, larger chips of coal or rock interfered with the
sample collection and plug compaction.
Results of this study support the conclusions reached in previous
studies by Owings et al. (1940), Saltsman and Grumer (1975),
Nagy (1981), and Sapko et al. (1987) that indicate that the roof
and rib dust samples should be kept separate from floor dust
samples and considered individually for analyses. A correlation
appears between the floor dust samples collected at varying depths
which indicates some mixing may have occurred from mining activities.
The practice of combining a sample depth of 2.5 cm from
the floor overwhelms the roof and rib portions of the overall
perimeter band sample. The presented data support the MSHA
procedure change to allow the combined roof and rib sample be
collected separately from the new 3-mm deep floor sample for a
more representative sample. However, it is advisable that the roof
and rib dust always be kept separate from the floor sample for
analysis