Environmental storage conditions influencing the filtration behavior of electret filters with repeated use

Abstract

Worldwide attention has been paid to effective protection strategies against the COVID-19 pandemic. Filtering masks are generally kept for a certain period of shelf-life before being used, and frequently, they are used repeatedly with recurrent storages. This study investigates the effect of storage temperature and humidity on the structural characteristics and charges of an electret filter, associating with the filtration performance in terms of efficiency and pressure drop based on a practical use-storage scenario. For the repeated use conditions with recurrent storage, humid storage conditions significantly deteriorated the filtration efficiency as hygroscopic particles quickly wetted the surface and masked the surface charges. The high temperature rapidly deteriorated the filter charges and caused a lowered electrostatic filtration efficiency. In a heated condition, the web became fluffier, yet it did not directly affect the pressure drop or mechanical filtration efficiency. The approach of this study is progressive in that rigorous analysis was performed on examining the particle morphology and internal structure of filter media with varied storage conditions to link with the filtration performance and the effective lifetime. This study intends to provide a scientific reference guiding a desirable storage condition and replacement cycle of filtering masks considering the actual use habits and storage environment.

Nanoweb for Nanobugs: Nanofiber Filter Media for Face Masks

“…For infectious diseases, the primary challenge is capturing the submicrometer-sized pathogens or “nanobugs”. While N95 respirators in particular exhibit greater than 95% filtration efficiency (FE) of 0.3 μm particles owing to their electret charge, this electret charge accumulation on the microfiber surface is only semidurable and can dissipate with storage time, repeat use, high humidity, − heat, , and disinfectant solvent. − Nanofibers have theoretically and experimentally been shown to collect greater than 95% of submicrometer particles with mechanical capture mechanisms alone (interception, inertial impaction, diffusion, and gravitational settling), allowing for storage-stable, reusable, and highly breathable core filter layers. , …”