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A DUST-SETTLING CHAMBER FOR SAMPLING-INSTRUMENT COMPARISON STUDIES
Citation:
O'Shaughnessy, P., E. Svendsen, P. S. Thorne, AND S. Reynolds. A DUST-SETTLING CHAMBER FOR SAMPLING-INSTRUMENT COMPARISON STUDIES. Presented at American Industrial Hygiene Assoc, San Diego, CA, June 1-6, 2001.
Description:
Introduction: Few methods exist that can evenly and reproducibly deposit dusts onto surfaces for surface-sampling methodological studies. A dust-deposition chamber was designed for that purpose.
Methods: A 1-m3 Rochester-type chamber was modified to produce high airborne dust concentrations (>25 mg/ m3) at a low flow rate (20 lpm) to facilitate settling onto test surfaces. To test the apparatus, sieved house-dust, recovered by a vacuum sampler from homes, was deposited onto carpet samples placed in the bottom of the chamber. A Wright Dust Feed aerosol generator was used to inject the dust directly into the top end of the chamber, through a screen-separated plenum, and into the main volume of the chamber. The use of a diffuser and large box fan placed in the plenum ensured adequate mixing of the aerosol and an even distribution of the aerosol entering the main chamber volume. Carpet samples were placed on a 0.9-m diameter turntable at the bottom of the chamber and rotated at 0.67 rpm to minimize the effect of spatial differences in dust concentration.
Results: Due to the low flow rate and large cross-sectional area of the chamber, a very low downward air-velocity of 80 mm/min was maintained. The low velocity maximized settling time and minimized turbulence in the chamber. To test surface loading variability, 47-mm filters were placed in a radial pattern on the turntable. Differences in mass collected on each filter resulted in a low CV of 0.183. A carpet dust loading of 13.6 g/m2, sufficient for sampling studies, was obtained within 2 hours.
Conclusion: A chamber/aerosolization system was developed that provided evenly-distributed dust over carpet samples within a relatively short time period. This method has the potential for many applications in surface-dust collection research.
Supported by NIEHS P30 ES05605-11. This abstract does not necessarily represent EPA policy.