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Correlation of Respirator Fit Measured on Human Subjects and a Static Advanced Headform

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OSTP Journal Article

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National Personal Protective Technology Laboratory Pittsburgh

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This study assessed the correlation of N95 filtering facepiece respirator FFR fit between a Static Advanced Headform StAH and 10 human test subjects. Quantitative fit evaluations were performed on test subjects who made three visits to the laboratory. On each visit, one fit evaluation was performed on eight different FFRs of various modelsize variations. Additionally, subject breathing patterns were recorded. Each fit evaluation comprised three two-minute exercises Normal Breathing, Deep Breathing, and again Normal Breathing. The overall test fit factors FF for human tests were recorded. The same respirator samples were later mounted on the StAH and the overall test manikin fit factors MFF were assessed utilizing the recorded human breathing patterns. Linear regression was performed on the mean log10-transformed FF and MFF values to assess the relationship between the values obtained from humans and the StAH. This is the first study to report a positive correlation of respirator fit between a headform and test subjects. The linear regression by respirator resulted in R2 0.95, indicating a strong linear correlation between FF and MFF. For all respirators the geometric mean GM FF values were consistently higher than those of the GM MFF. For 50 of respirators, GM FF and GM MFF values were significantly different between humans and the StAH. For data grouped by subjectrespirator combinations, the linear regression resulted in R2 0.49. A weaker correlation R2 0.11 was found using only data paired by subjectrespirator combination where both the test subject and StAH had passed a real-time leak check before performing the fit evaluation. For six respirators, the difference in passing rates between the StAH and humans was 20, while two respirators showed a difference of 29 and 43. For data by test subject, GM FF and GM MFF values were significantly different for 40 of the subjects.

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