The definitive version of this article appears in Journal of Occupational and Environmental Hygiene Volume 7, Issue 11, 2010, Pages 622 – 627. DOI: 10.1080/15459624.2010.513910 Published by Taylor & Francis.


The objective of this study was to compare size-selective workplace protection factors (WPFs) of an N95 elastomeric respirator (ER) and an N95 filtering facepiece respirator (FFR) in agricultural environments. Twenty-five healthy farm workers ranging in age from 20 to 30 years voluntarily participated in the study. Altogether eight farms were included representing three different types: two horse farms, three pig barns, and three grain handling sites. Subjects wore the ER and FFR while performing their daily activities, such as spreading hay, feeding livestock, and shoveling. Aerosol concentrations in an optical particle size range of 0.7–10 µm were determined simultaneously inside and outside of the respirator during the first and last 15 minutes of a 60-minute experiment. For every subject, size-selective WPFs were calculated in one-minute intervals and averaged over 30 minutes. For the ER, geometric mean WPFs were 172, 321, 1013, 2097 and 2784 for particles of 0.7–1.0, 1.0–2.0, 2.0–3.0, 3.0–5.0, and 5.0–10.0 µm, respectively. Corresponding values for the FFR were 69, 127, 324, 893, and 1994. The 5th percentiles for the ER and FFR were higher than the Assigned Protection Factor of 10 and varied from 28 to 250 and from 16 to 225, respectively. The results show that the N95 ER and FFR tested in the study provided expected level of protection for workers on agricultural farms against particles ranging from 0.7 to 10 µm. The WPFs for the ER were higher than those for the FFR in all size ranges, and the WPFs for both respirators increased with increasing particle size.


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