Quantitative fit-testing of N95 respirators: part II--results, effect of filter penetration, fit-test, and pass/fail criteria on respirator performance.
Coffey-CC; Zhuang-Z; Campbell-DL; Myers-WR
J Int Soc Respir Prot 1998 Jan; 16(1-4):25-36
This is the second of two articles dealing with quantitative fit-testing of N95 respirators (one of the new classes of particulate respirators) certified by the National Institute for Occupational Safety and Health in the United States. This portion of the study had three purposes to: 1) quantitatively fit-test twenty-one N95 respirators to evaluate the laboratory performance of these N95 respirators; 2) determine if their laboratory performance could be improved when the first donning was used as a surrogate fit-test to screen out poor fitting respirators; and 3) investigate the effect of face-seal leakage, pass/fail criteria, and the use of subsequent donnings as the surrogate fit-test on respirator performance. Each respirator was tested on a panel of 25 subjects with varying face sizes. Four total penetration tests were conducted for each subject/respirator combination resulting in a total of 100 measurements for each respirator. The 95th percentile for total penetrations of all the respirators combined was 33% which is more than three times the maximum allowable value of 10%. Further investigation revealed that the total inward leakage was mainly attributable to face-seal leakage, not filter penetration. When the first donning was used as a surrogate fit-test to separate the subjects into two groups (one passing the fit-test and one failing the fit-test), significant differences in the total penetration and face-seal leakage were found between the groups (p-value=0.0003). The results show that the level of protection provided by the N95 respirators is greatly enhanced when fit testing is performed to screen out poor fits. This study also demonstrated that the pass/fail criterion of 1% is necessary to insure that the respirator will reduce the in-facepiece concentration of workplace contaminants to 10% or less of the ambient concentration. In addition, it was found that the total penetration of face-seal leakage did not differ among the four different donnings. The subjects in this study were able to obtain consistent fits each time the respirator was donned. Thus, fit-testing protocols for N95 respirators may not have to include different donnings.
Respirators; Respiratory-equipment; Respiratory-protection; Performance-capability; Leak-prevention
Journal of the International Society for Respiratory Protection