Decontamination of SARS-CoV-2 and Other RNA Viruses from N95 Level Meltblown Polypropylene Fabric Using Heat under Different Humidities

Abstract

In March of 2020, the World Health Organization declared a pandemic of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The pandemic led to a shortage of N95-grade filtering facepiece respirators (FFRs), especially surgical-grade N95 FFRs for protection of healthcare professionals against airborne transmission of SARS-CoV-2. We and others have previously reported promising decontamination methods that may be applied to the recycling and reuse of FFRs. In this study we tested disinfection of three viruses, including SARS-CoV-2, dried on a piece of meltblown fabric, the principal component responsible for filtering of fine particles in N95-level FFRs, under a range of temperatures (60–95 °C) at ambient or 100% relative humidity (RH) in conjunction with filtration efficiency testing. We found that heat treatments of 75 °C for 30 min or 85 °C for 20 min at 100% RH resulted in efficient decontamination from the fabric of SARS-CoV-2, human coronavirus NL63 (HCoV-NL63), and another enveloped RNA virus, chikungunya virus vaccine strain 181/25 (CHIKV-181/25), without lowering the meltblown fabric’s filtration efficiency.

Disinfection Treatments of Disposable Respirators Influencing the Bactericidal/Bacteria Removal Efficiency, Filtration Performance, and Structural Integrity

“…About 5-log 10 fold reduction of SARS-CoV-2 under 95 • C for 5 min treatment [7] No drop in particle filtration efficiency under 100 • C, 50 min treatment Above 4-log 10 attenuation in Tulane virus, rotavirus, adenovirus [8] Small decrease in particle filtration efficiency under 100 • C for 15 min (about 1.5%)…”

“…Complete bactericidal efficiency of S. aureus [20] Microwaving No particle filtration efficiency drop for 2 min exposure NA [10] No particle filtration efficiency drop for 2.5 min exposure >4-log 10 reduction of E. coli for 2.5 min exposure with 500 W power [18] UV irradiation NA Complete bactericidal efficiency to B. subtilis spores [12] No particle filtration efficiency drop NA [7,10,12,17] Complete bactericidal efficiency of S. subtilis and E. coli [18] Small decrease in particle filtration efficiency (up to 1.25%) NA [16] Chlorinated disinfectant No drop in particle filtration efficiency after using hypochlorite wipe About 1-log 10 attenuation in S. aureus after using hypochlorite wipe [13] Decrease in particle filtration with increased pressure drop (up to 18.3%) NA [11] No effect on aerosol penetration efficiency NA [10,14] Ethanol Drastic decrease in filtration efficiency (up to 18%)…”

“…Complete suppression of bacterial growth after 5 min immersion [22] NA [7,19] Complete bactericidal efficiency of S. subtilis and E. coli [18] Isopropanol Decrease in particle filtration efficiency (over 5%) NA [11,17] Significant drop in oily aerosol filtration efficiency after 2 min immersion (up to around 40%) NA [9] Detergent -laundering Significant drop in particle filtration efficiency after soap solution soaking for 2 min (up to around 39%) NA [15] The particle filtration of an electret media is attributed to the mechanical capture and the electrostatic attraction of particles [31,32]. Many previous studies associated the deteriorated performance of disinfection-treated respirators with the loss of electrostatic charges [7,9,11,15,[17][18][19]22,25], yet the direct evidence of charge deterioration was often missing. Additionally, it has hardly been examined for the effect of treatment on the structural integrity of the filter media, which may affect the resistance of respirators.…”

“…As a contingency strategy for the capacity crisis of disposable respirators, the Centers for Disease Control and Prevention and the National Institute of Occupational Safety and Health announced the guidelines of potential disinfection methods for the reuse of disposable respirators, which include the application of ultraviolet (UV) germicidal irradiation, vaporous hydrogen peroxide (VHP), and moist heat [ 5 ]. Table 1 shows the summary of previous studies on respirator disinfection methods [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. As for the bactericidal efficiency, autoclaving, UV irradiation, and chemical solvent treatments using bleach, ethanol, and VHP showed up to a 99% reduction of tested bacteria or virus [ 21 , 25 , 26 , 27 , 28 , 29 , 30 ].…”

“…The particle filtration of an electret media is attributed to the mechanical capture and the electrostatic attraction of particles [ 31 , 32 ]. Many previous studies associated the deteriorated performance of disinfection-treated respirators with the loss of electrostatic charges [ 7 , 9 , 11 , 15 , 17 , 18 , 19 , 22 , 25 ], yet the direct evidence of charge deterioration was often missing. Additionally, it has hardly been examined for the effect of treatment on the structural integrity of the filter media, which may affect the resistance of respirators.…”