Page:NIOSH DM DFM respirator evaluation draft.pdf/71

for various respirator classes, the first Hyatt et al. guide contained a column for "filter efficiency, %" with values for both NaCl and DOP. The reported filter efficiencies against NaCl were 75% to 90% (25% to 10% filter leakage) for four DM-filter classes: single use, 1/4 or 1/2; dust filters on 1/4 and 1/2 facepieces, and dust filters on powered 1/2 facepieces.^[1] Additionally, the reported filter efficiencies against NaCl were 95% to 99% (5% to 1% filter leakage) for three DFM-filter classes: fume filters on 1/4 and 1/2 facepieces and fume filters on powered 1/2 facepieces. 167 The second LASL selection guide reported by Hyatt et al. (their Table XVII) had the filter-efficiency values removed and only "selection guide multiples of TWA for 8 hr. day" were reported. 168 Their second Table XVII contained a footnote 2 stating: Contaminants include gases, vapors, dusts, fumes, and mists. Each type of specific contaminant would have to be considered as to the size if it is a dust, fume, or mist, and the sorbent if a gas or vapor. Example, sulfuric acid mist criteria-concentrated sulfuric acid mist gives off SO,, which is very fine and requires a high efficiency filter. It is known that dust filters are satisfac tory for dilute sulfuric acid mist. 169 Hyatt et al. also stated regarding their second Table XVII: Table XVI differs from Table XVII in several ways, a major one being the different protection factors (PF's) for various types of devices.... The selection guide of 10X time-weighted average (TWA) for both dust and fume respirators is based on new quantitative man tests on dust respi- rator facepieces equipped with high efficiency filters. This permits the measurement of facepiece leakage only, on both quarter and half facepieces. The data indicated that both types will pass the criteria for a protection factor of 10, based on facepiece leakage only. 170 In 1975, the Executive Director of the Industrial Safety Equipment Association, Inc. (ISEA), sent comments from the Respirator Group of the ISEA. The ISEA “rep- resents virtually all the manufacturers of respirators."1" The ISEA provided their analysis of respirator filter and face-seal performance data obtained at the Los

187Tbid., Table XVI, p. 40. 1Tbid., Table XVII, pp. 41-42. 18Tbid., p. 41. 170 Tbid., p. 36. 171Wilcher, F. E.: Letter to J. Donald Millar of NIOSH from F. E. Wilcher, President, ISEA, Arlington,

Virginia (September 23, 1986).