Challenges in Predicting the Filtration Performance of a Novel Sewn Mask: Scale-up from Filter Holder to Mannequin Measurements

Challenges in Predicting the Filtration Performance of a Novel Sewn Mask: Scale-up from Filter Holder to Mannequin Measurements

Abstract Novel designs and materials for filtering face-piece respirators (FFRs) have been disseminated in response to shortages during the COVID-19 pandemic. Since filtration efficiency depends on particle diameter and air face velocity, the relevance of material filtration or prototype fit data de...

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Bibliographic Details
Main Authors: Audrey J. Dang, Benjamin M. Kumfer, J. Tyler Bertroche, Jane Olson Glidden, Christopher R. Oxford, Udayabhanu Jammalamadaka, Mary Ruppert-Stroescu, Alexander R. Scott, Jason A. Morris, Connie Gan, Jesse Hu, Bradley King, David I. A. Dhanraj, Shruti Choudhary, Pratim Biswas, Richard L. Axelbaum, Kathleen W. Meacham, Brent J. Williams
Format: Article
Language:English
Published: Springer 2021-04-01
Series:Aerosol and Air Quality Research
Subjects:
Respirator
Filtration
Face velocity
COVID-19
Mask
Online Access:https://doi.org/10.4209/aaqr.200629
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Summary:Abstract Novel designs and materials for filtering face-piece respirators (FFRs) have been disseminated in response to shortages during the COVID-19 pandemic. Since filtration efficiency depends on particle diameter and air face velocity, the relevance of material filtration or prototype fit data depends on test conditions. We investigate whether characterizing a material in a filter holder at a range of face velocities enabled precise prediction of the filtration performance of a novel sewn mask design. While larger particles (> 500 nm) are more relevant for inhalation exposure to respiratory emissions, we compare this mask and a N95 FFR (as a control) with smaller particles more similar to those in the N95 test method. Sewn from sterilization wrap, our mask (sealed to a mannequin head with silicone) filters 85 ± 1% of 136 nm particles (NaCl, 85 L min−1) and passes quantitative fit tests for 4 of 6 volunteers, representing intermediate protection between a surgical mask and N95 FFR. Filter holder material measurements overpredict the sewn mask’s filtration efficiency by 8.2% (95% CI 7.4–9.1%) (136 or 200 nm). While testing flat material in a filter holder enables comparison between materials, filtration performance does not precisely scale-up from filter holder to mannequin tests. Testing full prototypes at relevant conditions is crucial if an improvised design is intended as a substitute for a commercial surgical mask or FFR.
ISSN:1680-8584
2071-1409

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