Page:NIOSH DM DFM respirator evaluation draft.pdf/62

This page needs to be proofread.
54
Performance Evaluation of DM and DFM Filter Respirators—WORKING DRAFT 9.15.92

possbility of nonsampling errors and biases must be explored. First, NIOSH noted that the computed failure rates were observed in WPF Studies representing optimal wearing conditions in which the lowest possible failure-rate results should have been obtained. These optimal conditions include fit testing of all test subjects with OSHA-approved fit tests.
  Second, none of the nine studies used a NIOSH-type deep probe to measure the in-mask concentrations. Failure to use this type of probe can erroneously overestimate all WPFs by up to 100% due to measurement bias.[1][2]
  Third, eight of the nine studies[3] did not correct the observed WPF measurements for lung retention of inhaled aerosols. Failure to perform this correction can erroneously overestimate all WPFs by 10% to 30% due to measurement bias.[4][5][6][7]

Fourth, none of the eight studies!“ investigating WPF's in workplaces with aero- sol contaminants corrected the observed WPF measurements for filter-holder wall deposition. In the Pallay et al. study, it was reported that this deposition averaged 18% for the ambient-air samples (outside a respirator) and 61% for the in-face sam- ples (inside a respirator).’“5 This magnitude of difference in the proportion of con- taminant lost to the filter-holder wall can erroneously overestimate all WPFs by a substantial amount due to measurement bias. Results reported by Pallay et al. indi- *






“


‘Studies numbers 2 through 6 in Table O of this evaluation. “Pallay, B.: Workplace Protection Factor Study of Half-Facepiece Particulate Air Purifying Respirators

at Two Lead-Acid Battery Manufacturing Facilities, Paper presented at the 1991 American Industrial

Hygiene Conference, Salt Lake City, Utah (May 22, 1991).

  1. ↑ Myers, W.R., J. Allender, R. Plummer, and T. Stobbe: Parameters that Bias the Measurement of Airborne Concentration Within a Respirator, Am. Ind. Hyg. Assoc. J. 47(2):106-114 (1986).
  2. ↑ Myers, W.R., J.R. Allender, W. Iskander and C. Stanley: Causes of In-Facepiece Sampling Bias—I. Half-Facepiece Respirators, Ann. Occ. Hyg. 32(3):345-359 (1988).
  3. ↑ Studies numbers 2 through 8 in Table O of this evaluation.
  4. ↑ Holton, P. M. and K. Willeke: The Effect of Aerceol Size Distribution and Measurement Method on Respirator Fit, Am. Ind. Hyg. Assoc. J. 48(10):885-860 (1987), Figure 1, p. 856.
  5. ↑ Hounam, R. F., D. J. Morgan, D. T. O'Conner, and R. J. Sherwood: The Evaluation of Protection Afforded by Respirators, Ann Occup, Hyg. 7:353-363 (1964), pp. 361-362.
  6. ↑ Galvin, K., S. Selvin, and R. C, Spear: Variability in Protection Afforded by Half-Mask Respirators Against Styrene Exposure in the Field, Am. Ind. Hyg. Assoc. J. 51:625-639 (1990), p. 628.
  7. ↑ Pallay, B.: Workplace Protection Factor Study of Half-Facepiece Particulate Air Purifying Respirators at Two Lead-Acid Battery Manufacturing Facilities, paper presented at the 1991 American Industrial Hygiene Conference, Salt Lake City, Utah (May 22, 1981).
This article is issued from Wikisource. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.