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WORKING DRAFT 9.15.92—Performance Evaluation of DM and DFM Filter Respirators

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Table N—Summary of Evaluation of Professional Practices Used During the 1970, and 1980s for Face-Seal Evaluations and APF Determinations.

Process Element	Comments on 1970's Laboratory Evaluations and APFs	Comments on 1980's Workplace Evaluations and APFs
1—Select respirators to be tested.	Many if not most available models in each respirator class were tested. Hence the worst performers in each class generally were tested and considered when setting APFs.	Respirators tested were not necessarily the worst in each class, perhaps even the better ones were tested. Thus the worst in each class were not necessarily considered when setting APFs.
2—Select test environment.	Laboratory test chambers with subjects undergoing limited maneuvers to stress fit of respirators. Small-size test areosols used to measure mask performance.	Workplaces under optimal, ideal use conditions. Performance was measured during routine job activities. Contaminants occurring in workplaces were used to measure mask performance.
3—Select test environment.	Test panels were selected with intent of representing 95% of facial sizes in U.S. population.	Any available facial sizes were used. Smaller and larger facial sizes may not have been tested, which are the sizes most expected to show poor respirator performance due to face-seal leakage.
4—Perform fit-test screening (QLFT or QNFT) to eliminate those subjects unable to obtain an adequate fit.	Generally a QLFT-type irritant fume fit test was used for fullface masks only. No fit testing was used before halfmask performance testing.	Generally the saccharin QLFT was used. A few stuides used other QLFTs or QNFT.
5—Measure respirator leakages under test conditions.	These results were later shown in the 1980's to have no correlation with results measured in the workplace.	Two to three measurement biases were present in most studies. Thus the reported WPFs generally overestimated the actual WPFs and reported APFs.
6—Analyze leakage data and determine APFs for each respirator class.	After proper fit testing has been conducted by the employer, 100% of respirator wearers are required to achieve a class APF in the workplace. Class APF set at 5th percentile PF observed in panel subjects wearing worst respirator(s) in each class. It is expected that up to 10% of American workers cannot acheive the class APF with the worst respirator (i.e., up to 5% of test subjects not achieving APF plus 5% of U.S. facial sizes not represented on that panel) before proper fit testing is performed. However, proper fit testing has not been demonstrated to be capable of identifying 100% of those fits less than class APFs. Thus from less than 1% to substantially more than 10% of American workers will not achieve a computed APF while wearing air-purifying, laboratory-tested respirators under ideal conditions in the workplace.	After proper fit testing has been conducted by the employer, only 95% of respirator wearers are required to achieve a class APF in the workplace. APFs for measured respirators are set at 5th percentile WPF observed in test subjects after proper fit testing has been performed. Additionally, no consideration made for large uncertainty in 5th percentile WPF estimates due to statistical sampling error. Panels may represent substantially less than 95% of U.S. facial sizes. Thus from less than 1% to substantially more than 10% of American workers will not achieve a computed APF while wearing air-purifying, workplace-tested respirators under ideal conditions in the workplace.