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Investigation of collection efficiencies and inhalation convention conformity of portable microbial samplers.

Yao-M; Mainelis-G
Proceedings of the AAAR 24th Annual Conference, October 17-21, 2005, Houston, Texas. Mount Laurel, NJ: American Association for Aerosol Research, 2005 Oct; :104
Accurate bioaerosol exposure estimates require advanced microbial samplers, especially those that follow convention for inhalable airborne particles. Currently, the use of portable microbial samplers is increasing. However, little information is available about the performance characteristics of such samplers, including their conformity to inhalable particle convention. The objective of this study was to investigate the physical collection efficiencies and conformity to inhalation convention of several portable microbial samplers including RCS HighFlow, BioCulture, Microflow, Microbiological Air Sampler (MAS) and SMA MicroPortable. All these samplers collect biological particles on agar media and their built-in sampling flow rates range from 30 to 141.5 L/min. The physical collection efficiencies of portable samplers were determined using Polystyrene Latex particles ranging from 0.5 to 5.22 um in aerodynamic size. Our investigation revealed that a classical collection efficiency testing approach, which compares particle concentrations upstream and downstream of a sampler, cannot directly be applied to these portable samplers because many of them feature air movers positioned next to the sampling media and act as particle collectors themselves. Therefore, we developed a new testing procedure which allows differentiating the collection efficiency between the collection media (agar) and the air movers, thus allowing estimation of effective collection efficiency, i.e., fraction of incoming particles deposited on collection medium. Experimental results have shown that all evaluated samplers collect approximately 5% of 0.5 um particles. The effective d50, or cut-off sizes, of the investigated samplers depended on the sampler model and ranged from 1.2 um for the RCS High Flow operating at 100 L/min to 2.8 um for the MAS sampler operating at 100 L/min; the effective cut-off sizes for other three samplers (SMA Microportable operating at 141.5 L/min, BioCulture operating at 120 L/min and Microflow operating at 120 L/ min) were above 5.2 um. The experimental cut-off sizes of the portable samplers agreed well with their theoretical estimates. Comparison of the samplers' collection characteristics with the sampling convention for total inhalable particles revealed that relative to the inhalation convention most of the investigated portable microbial samplers would under-sample particles between 0.5-5.2 um, a size range which encompasses most of the single bacterial and fungal particles. The obtained results indicate that application of the tested portable bioaerosol samplers for biological exposure assessment may result in underestimation of the airborne microorganism concentrations. As the continuation of this study, the biological performances of the portable bioaerosol samplers will be determined.
Bacteria; Samplers; Sampling-equipment; Sampling; Air-monitoring; Air-samplers; Air-sampling; Air-sampling-equipment; Health-hazards; Humans; Fungi; Particulate-dust; Particulates
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Proceedings of the AAAR 24th Annual Conference, October 17-21, 2005, Houston, Texas
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Rutgers, The State University of New Jersey, New Brunswick