Particle blow-off: a source of error in blunt dust samplers

From blunt sampler theory it is possible to predict over-sampling for simple single-orifice, axisymmetric “total dust” samplers (such as the Casella type T13032) arising from particle blow-off from external surfaces. Wind tunnel experiments confirmed the predicted broad trends, revealing the errors in question to be as large as 50% for the sampling of dry dusts under some conditions of practical relevance. The results suggest that the laboratory evaluation of dust samplers in general ought to be carried out using test aerosols whose physical characteristics approximate as closely as possible those expected in practice.