Evaluation of the benefit of the user seal check on N95 filtering facepiece respirator fit

The objective of this study was to better understand the benefit of the user seal check step for respirator test subjects in the N95 filtering facepiece respirator donning process. To qualify for the study, subjects were required to pass a standard quantitative fit test on at least one of the three N95 filtering facepiece respirator models: 3M 1860 (cup), 3M 1870 (flat-fold), and Kimberly Clark PFR95-270 (duckbill). Eleven subjects were enrolled and performed a series of abbreviated, quantitative fit tests where they were randomly asked either to perform or not perform a user seal check with 20 different respirator samples of each model. The experimental design included 3 respirator models × 10 subjects × 2 treatment levels with 10 replications. Geometric mean (GM) fit factors and percentages of times a fit factor ≥ 100 was achieved for a donning were compared for each subject with and without the user seal check across all models and for each model. Higher GM fit factors and smaller geometric standard deviations across all models were achieved for 10 of the 11 subjects when performing a user seal check compared with not performing a user seal check. Geometric mean fit factors of 148, 184, and 156, compared with 126, 187, and 115, respectively, were obtained for the 3M 1860, 3M 1870, and Kimberly Clark PFR95-270 models when the user seal check was performed vs. not performed. Differences in the GM fit factors for the 3M 1860 and Kimberly Clark PFR95-270 models were statistically significant (p < 0.05) when performing a user seal check vs. not performing a user seal check. These data suggest that there may be some benefit to performing the user seal check for at least some models during the filtering facepiece respirator donning process for workers who have previously passed a fit test for those respirator models. Additional research is needed with larger groups of subjects and respirator models/types.