Characterization of the fiber diameter distributions of synthetic mineral fiber products and their dusts.

Procedures to measure the fiber diameter distributions of bulk synthetic mineral fiber products in order to characterize product differences and the diameters of airborne fibers emitted from them have been investigated. Bulk fibers were prepared for size measurement by two methods--one that gently teased fibers apart and another that lightly ground them in a liquid slurry. Bulk products exhibited different contents of respirable fibers, but these were significantly greater when products were prepared by grinding rather than teasing. This was established to result from preferential breakdown of finer fibers into shorter lengths with the former method. Airborne fibers emitted during work operations with products had diameter distributions similar to those of ground fibers, indicating that similar breakdown of finer fibers into shorter lengths occurs for dusts emitted during such operations.