RESPIRABLE DUST SAMPLERS FOR USE IN MINING
The most common type of sampler used in the mining industry is the gravimetric sampler, which
is designated by the Federal Coal Mine Health and Safety Act of 1969 for use in compliance dust
sampling (Figure 2-1).
Figure 2-1. Gravimetric sampling pump, cyclone and filter cassette.
This sampler consists of a constant-flow sampling pump, a size-selective
cyclone, and a filter cartridge. In metal/nonmetal mining operations, the pump should be
operated at 1.7 lpm. The 10-mm Dorr-Oliver cyclone separates the oversize dust from the
respirable fraction (usually considered to have an aerodynamic diameter of 10 microns or less).
The oversize dust is deposited into the grit pot at the bottom of the cyclone, while the respirable
fraction is deposited onto a 37-mm-diameter polyvinyl chloride (PVC) filter. Care must be taken
after a sample is collected to ensure that the cyclone assembly stays in an upright position.
Otherwise, the oversize dust particles that are in the grit pot can be deposited onto the filter and
invalidate the sample. The filter collects the respirable dust and is weighed to determine the mass
of dust that has been collected during sampling. The mass of dust and the volume of sampled air
are used to calculate the average concentration of respirable dust in mg/m3
.