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

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 air face velocity, relevance of material or prototype fit data test conditions. We investigate whether characterizing a filter holder at range velocities enabled precise prediction performance novel sewn mask design. While larger particles (> 500 nm) are more relevant inhalation exposure respiratory emissions, we compare this N95 FFR (as control) with smaller similar those method. Sewn from sterilization wrap, our (sealed mannequin head silicone) filters 85 ± 1% 136 nm (NaCl, L min–1) passes quantitative tests 4 6 volunteers, representing intermediate protection between surgical FFR. Filter measurements overpredict mask’s by 8.2% (95% CI 7.4–9.1%) (136 200 nm). testing flat enables comparison materials, does not precisely scale-up tests. Testing full prototypes conditions is crucial if an improvised design intended as substitute commercial