Transmission of aerosols through pristine and reprocessed N95 respirators

Abstract

During the Covid-19 pandemic, pristine and reprocessed N95 respirators are crucial equipment towards limiting nosocomial infections. The NIOSH test certifying the N95 rating, however, poorly simulates aerosols in healthcare settings, limiting our understanding of the exposure risk for healthcare workers wearing these masks, especially reprocessed ones. We used experimental conditions that simulated the sizes, densities and airflow properties of infectious aerosols in healthcare settings. We analyzed the penetration and leakage of aerosols through pristine and reprocessed N95 respirators. Seven reprocessing methods were investigated. Our findings suggest that pristine and properly reprocessed N95 respirators effectively limit exposure to infectious aerosols, but that care must be taken to avoid the elucidated degradation mechanisms and limit noncompliant wear.

A systematic review of mask disinfection and reuse for SARS-CoV-2 (through July 10, 2020)

“…Given the wide differences in test conditions, results are summarized by disinfection agent for N95s only, for agents with >5 samples or those agents identified in the disinfection efficacy section as achieving >3 log reduction of SARS-CoV-2, including ethanol, hydrogen peroxide, peracetic acid, PX-UV, UVGI, autoclaving, and heat. Autoclaving (n=14) 14,30,34,42,45,55,57,59 and ethanol disinfection (n=14) 15-17, 29, 42, 45, 53, led to failures within two disinfection cycles in 12 and 13 tests, respectively. This indicates these methods cannot be utilized for N95 reuse.…”

“…Hydrogen peroxide disinfection (n=20) 15,19,27,29,30,36,45,51,57,[59][60][61]68 , dry heat (n=19) 12, 16, 19, 21, 29, 33-35, 42, 45, 49, 50, 52, 54 , UVGI (n=13) 15,16,29,35,42,45,46,52,[59][60][61][62] , and ethylene oxide (n=5) 19,[59][60][61] all had promising results.…”

Decontamination and Reuse of N95 Filtering Facepiece Respirators: Where Do We Stand?

“…Other studies, some with limited numbers and varied fit tests, noted preserved fit after dry heat at 70°C × 30 minutes, 70°C × 60 minutes, 65 75°C × 30 minutes., and a dry rice cooker 149–164 °C × 3 minutes. 70 Chen et al 71 found well-preserved fit and filtration up to 3 cycles of both dry heat at 75°C × 60 minutes and 100°C × 30 minutes at 75%RH. Fischer et al 52 found some fit failures after the third 70°C heat cycle.…”

“… 53 , 78 Another recent report of the effects on 0.3 μm particle penetration of 7 FFR decontamination methods found very little change after 10 VHP cycles but damage after the third HPGP cycle, using 3 N95 models. 71 Pressure gradient data suggest that all methods damaged filter function by weakening the electret. 71 Filter damage following plasma and ionized methods may be related to higher HP concentrations.…”

“… 71 Pressure gradient data suggest that all methods damaged filter function by weakening the electret. 71 Filter damage following plasma and ionized methods may be related to higher HP concentrations. Cramer et al 83 reported on a low concentration i-HP technique (TOMI, Beverly Hills, CA) that is compatible with cellulose-containing PPE.…”