Abstract
There are several logical objectives for dust samples used in biomedical research. Obviously, the dusts used should closely resemble natural mine dusts with respect to particle size distribution, particle shape, and composition. These characteristics must be consistent from sample to sample. Usually the relative freshness of the dust is also of primary concern. A generalized procedure for producing dust by single- or multiple-stage grinding and classification has been developed. Three laboratory-scale grinding devices—a Bleuler rotary mill (ring and puck grinder), a Retsch high speed planetary mill, and a Sweco vibratory mill—have been tested. The results have been evaluated in terms of the product size distribution, particle shape, and contamination introduced in the grinding process. All three devices have been found to be capable of producing appropriate size distributions at acceptable contamination levels. Multistage grinding with intermediate classification steps generally provides angular particles of similar shape to those found in natural dusts. Several alternatives for producing fresh dust for immediate use in biomedical experimentation, including the use of storage systems to maintain freshness, are evaluated. Evaluation of one common procedure—regrinding of previously prepared dust—reveals that this approach can lead to significant alteration of coal structures and reagglomeration of fine, respirable-size particles.