Page:NIOSH DM DFM respirator evaluation draft.pdf/69

8—Review and evaluation of reports, research findings, and recommendations concerning the nature of leakage through DM and DFM filters certified by NIOSH under 30 CFR Part 11.

  As part of its efforts to prepare APFS values for this evaluation, NIOSH conducted a thorough review of relevant material pertaining to the issue of possible contaminant leakage through DM and DFM filters. The Institute's review included research data, findings, and recommendations that have been reported in the professional literature over the last two decades and in nonconfidential research reports and committee recommendations. The NIOSH conclusions stated in this section are based on the best available evidence from the last two decades regarding the efficacy of DM and DFM filters.
  Over the last twenty years, numerous reports have appeared in the professional literature on the subject of leakage through NIOSH-certified DM and DFM filters. Substantial filter leakage has been reported to occur for contaminant sizes that typically range from about 0.05 to 0.40 micrometers (μm) count median diameter (CMD). Filter leakage of particles with aerodynamic mean sizes up to 2.5 μm has been reported through one type of NIOSH-certified DM filtering-facepiece mask.
  In 1971, Mitchell et al. published the results of using a 0.05 μm CMD (geometric standard deviation (GSD) of 2.22) NaCl aerosol to test several DM and DFM filters that were approved at that time by the U.S. Bureau of Mines. 153 For three models of DM filters tested at 42.5 L/min/filter, they reported filter leakages of 3.8%, 40.0%, and 44.0%.154 For three models of DFM filters also tested at 42.5 L/min/filter, they reported filter leakages of 6.5%, 12.5%, and 24.5%.155 In 1972, Ferber et al. reported the use of a 0.15 μm CMD (GSD of 1.9) NaCl aero- sol to test 13 DM and 6 DFM filters that were commercially available and approved by the U.S. Bureau of Mines. 156 For the 13 DM filters tested at 42.5 L/min/filter, they reported filter leakages of 31%, 27%, 24%, 18%, 13%, 12%, 11%, and the rest 15 Mitchell, R.N., D. A. Bevis, and E. C. Hyatt: Comparison of Respirator Filter Penetration by Dioctyl Phthalate and Sodium Chloride, Am. Ind. Hyg. Assoc. J., 32:357-364 (1971). 154Tbid., Table III, p. 362. 155Ibid., Table II, p. 361. 150 Ferber, B. I., F. J. Brenenborg, and A. Rhode: Penetration of Sodium Chloride Aerosol through Respirator Filters, Am. Ind. Hyg. Assoc. J., 33(12):791-796 (1972).