Development and evaluation of an inhalable bioaerosol manifold sampler

This paper describes the development and evaluation of an inhalable bioaerosol manifold sampler for the collection of replicate samples over sequential sampling periods. Wind tunnel experiments at wind velocities less than or equal to 0.6 m/sec (less than or equal to similar to 120 ft/min) and at a sampling velocity of 0.6 m/sec yielded sampling efficiencies within 10% of the American Conference of Governmental Industrial Hygienists' inhalable curve up to particle diameters for about 18 mu m and efficiencies within 18% for diameters up to 26 mu m. At wind velocities greater than or equal to 0.6 m/sec, a sampling velocity of 0.8 m/sec yielded efficiencies that were within 15% of the inhalable curve up to diameters of about 22 mu m and within 20% for diameters up to 25 mu m. Microscopic counts of 15.6-mu m and 25.6-mu m monodisperse polystyrene beads aerosolized in the wind tunnel and collected with the manifold sampler yielded precise concentrations (pooled CV=9.0 and 5.3%, respectively) averaging 115% and 92%, respectively of measurements with the APS Model 3310 aerodynamic particle sizer. Field tests in a cotton dust environment demonstrated the ability to generate a time/concentration profile of fungal spores similar to that indicated for cotton dust levels determined with horizontal elutriators. Cotton dust was sampled efficiently while cotton fibers were excluded. Field tests on a dairy farm indicated no statistically significant bias (p=0.72) between spore concentrations determined with the manifold sampler and concentrations determined through a central test port.