Annals of Occupational Hygiene Advance Access originally published online on October 14, 2006
Annals of Occupational Hygiene 2007 51(2):143-151; doi:10.1093/annhyg/mel073
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Published by Oxford University Press
Physical Collection Efficiency of Filter Materials for Bacteria and Viruses
1 Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health 4676 Columbia Parkway, MS R-11, Cincinnati, OH, 45226, USA
2 Department of Environmental Health, University of Cincinnati PO Box 670056, Cincinnati, OH 45267, USA
*Author to whom correspondence should be addressed. Tel: +1-513-841-4323; fax: +1-513-458-7147; e-mail: NBurton{at}cdc.gov
The purpose of this study was to determine the physical collection efficiency of commercially available filters for collecting airborne bacteria, viruses, and other particles in the 10–900 nm (nanometer) size range. Laboratory experiments with various polytetrafluoroethylene (PTFE), polycarbonate (PC) and gelatin filters in conjunction with ButtonTM Inhalable samplers and three-piece cassettes were undertaken. Both biological and non-biological test aerosols were used: Bacillus atrophaeus, MS2, polystyrene latex (PSL), and sodium chloride (NaCl). The B.atrophaeus endospores had an aerodynamic diameter of 900 nm, whereas MS2 virion particles ranged from 10 to 80 nm. Monodisperse 350 nm PSL particles were used as this size was believed to have the lowest filtration efficiency. NaCl solution (1% weight by volume) was used to create a polydisperse aerosol in the 10–600 nm range. The physical collection efficiency was determined by measuring particle concentrations size-selectively upstream and downstream of the filters. The PTFE and gelatin filters showed excellent collection efficiency (>93%) for all of the test particles. The PC filters showed lower collection efficiency for small particles especially <100 nm. Among the tested filters, the lowest collection efficiencies, 49 and 22%, were observed for 1 and 3-µm pore size PC filters at the particle sizes of 47 and 63 nm, respectively. The results indicate that the effect of filter material is more significant for the size range of single virions than for bacteria. The effect of filter loading was examined by exposing filters to mixtures of PSL particles, which aimed at mimicking typical indoor dust levels and size distributions. A 4-h loading did not cause significant change in the physical collection efficiency of the tested filters.
Keywords: bacteriophages • collection efficiency • endospores • gelatin • polycarbonate • polytetrafluoroethylene
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