Simulated workplace performance of N95 respirators

During July 1995 the National Institute for Occupational Safety and Health (NIOSH) began to certify nine new classes of particulate respirators. To de termine the level of performance of these respirators, NIOSH researchers co nducted a study to (1) measure the simulated workplace performance of 21 N9 5 respirator models, (2) determine whether fit-testing affected the perform ance, and (3) investigate the effect of varying fit-test pass/fail criteria on respirator performance. The performance of each respirator model was me asured by conducting 100 total penetration tests. The performance of each r espirator model was then estimated by determining the 95th percentile of th e total penetration through the respirator (i.e., 95% of wearers of that re spirator can expect to have a total penetration value below the 95th percen tile penetration value). The 95th percentile of total penetrations for each respirator without fit-testing ranged from 6 to 88%. The 95th percentile o f total penetrations for all the respirators combined was 33%, which exceed s the amount of total penetration (10%) normally expected of a half-mask re spirator. When a surrogate fit test (1% criterion) was applied to the data, the 95th percentile of total penetrations for each respirator decreased to 1 to 16%. The 95th percentile of total penetrations for all the respirator s combined was only 4%. Therefore, fit-testing of N95 respirators is necess ary to ensure that the user receives the expected level of protection. The study also found that respirator performance was dependent on the value of the pass/fail criterion used in the surrogate fit-test.