INSTRUMENTATION OF RESPIRABLE DUST GENERATED IN WOOD PROCESSING AND ITS CLLECTION METHOD

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To investigate effects of sanding conditions on concentration of respirable wood dust and stock removal rate under belt sanding, the concentrations in wood under various conditions were measured using the respirable aerosol mass monitor, experimentally designed by the orthogonal array. We adopted grain size of coated abrasive, sanding condition, sanding time, sanding pressure and sanding direction as sanding conditions. Analysis of variance was used to examine the impacts in term of geometric mean, maximum and geometric standard deviations of measured concentrations, as well as stock removal rate. Stock removal rate was affected by grain size of coated abrasive, sanding pressure and sanding direction, but the respirable dust concentration was only influenced by sanding pressure, and linearly increased with increasing sanding pressure. Relationship between sanding pressure and geometric mean of respirable dust concentration could be expressed by the equation under the experimental conditions. On the other hand, the distribution of airborne dust in a woodworking chamber was measured. The shape of fine particles that fell onto a glass plate were also analyzed by an image analyzer, and the distribution of the diameter and other shape factors of the particles were estimated. The changes in the dust concentration in the diameter distribution with time were simulated by a numerical analysis which considered the drug due to friction between air and particles in free fall. The calculated density agreed favorably with the measured value. The effects of both the particle shape and the sanding conditions on the simulation were also clarified.