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. 2021 May 19;16(5):e0251872.
doi: 10.1371/journal.pone.0251872. eCollection 2021.

"Don, doff, discard" to "don, doff, decontaminate"-FFR and mask integrity and inactivation of a SARS-CoV-2 surrogate and a norovirus following multiple vaporised hydrogen peroxide-, ultraviolet germicidal irradiation-, and dry heat decontaminations

Louisa F Ludwig-Begall  1 , Constance Wielick  1 , Olivier Jolois  2 , Lorène Dams  1 , Ravo M Razafimahefa  1 , Hans Nauwynck  3 , Pierre-Francois Demeuldre  4 , Aurore Napp  4 , Jan Laperre  2 , Etienne Thiry  1 , Eric Haubruge  5
Affiliations

"Don, doff, discard" to "don, doff, decontaminate"-FFR and mask integrity and inactivation of a SARS-CoV-2 surrogate and a norovirus following multiple vaporised hydrogen peroxide-, ultraviolet germicidal irradiation-, and dry heat decontaminations

Louisa F Ludwig-Begall et al. PLoS One. .

Abstract

Background: As the SARS-CoV-2 pandemic accelerates, the supply of personal protective equipment remains under strain. To combat shortages, re-use of surgical masks and filtering facepiece respirators has been recommended. Prior decontamination is paramount to the re-use of these typically single-use only items and, without compromising their integrity, must guarantee inactivation of SARS-CoV-2 and other contaminating pathogens.

Aim: We provide information on the effect of time-dependent passive decontamination (infectivity loss over time during room temperature storage in a breathable bag) and evaluate inactivation of a SARS-CoV-2 surrogate and a non-enveloped model virus as well as mask and respirator integrity following active multiple-cycle vaporised hydrogen peroxide (VHP), ultraviolet germicidal irradiation (UVGI), and dry heat (DH) decontamination.

Methods: Masks and respirators, inoculated with infectious porcine respiratory coronavirus or murine norovirus, were submitted to passive decontamination or single or multiple active decontamination cycles; viruses were recovered from sample materials and viral titres were measured via TCID50 assay. In parallel, filtration efficiency tests and breathability tests were performed according to EN standard 14683 and NIOSH regulations.

Results and discussion: Infectious porcine respiratory coronavirus and murine norovirus remained detectable on masks and respirators up to five and seven days of passive decontamination. Single and multiple cycles of VHP-, UVGI-, and DH were shown to not adversely affect bacterial filtration efficiency of masks. Single- and multiple UVGI did not adversely affect respirator filtration efficiency, while VHP and DH induced a decrease in filtration efficiency after one or three decontamination cycles. Multiple cycles of VHP-, UVGI-, and DH slightly decreased airflow resistance of masks but did not adversely affect respirator breathability. VHP and UVGI efficiently inactivated both viruses after five, DH after three, decontamination cycles, permitting demonstration of a loss of infectivity by more than three orders of magnitude. This multi-disciplinal approach provides important information on how often a given PPE item may be safely reused.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Experimental set-up of filtering facepiece respirator (FFR) and surgical mask (SM) decontamination assays.
(A) Natural virus degradation over time. (B) Integrity testing after multiple-cycle vaporised hydrogen peroxide (VHP), ultraviolet germicidal irradiation (UVGI), and dry heat (DH) decontamination. (C) Multiple-cycle decontamination of porcine respiratory coronavirus (PRCV)- and murine norovirus (MuNoV)- inoculated SMs/FFRs.
Fig 2
Fig 2. Recovery of porcine respiratory coronavirus (PRCV) after elution from filtering facepiece respirators (FFRs) and surgical masks (SMs) kept at room temperature (20°C) over time.
PRCV infectivity was analysed in swine testicular cells. The cell culture limit of detection (LOD) was 0.80 log10 TCID50/mL (6.31×100 TCID50/mL).
Fig 3
Fig 3. Recovery of murine norovirus (MuNoV) after elution from filtering facepiece respirators (FFRs) and surgical masks (SMs) kept at room temperature (20°C) over time.
MuNoV infectivity was analysed in RAW264.7 cells. The cell culture limit of detection (LOD) was 0.80 log10 TCID50/mL (6.31×100 TCID50/mL).
Fig 4
Fig 4. Filtering facepiece respirator (FFR) NaCl filtration efficiency- and surgical mask (SM) bacterial filtration efficiency (BFE) testing after single-cycle or multiple-cycle decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Horizontal dashed lines represent the NaCl filtration efficiency requirement of ≥95% according to NIOSH 42 CFR Part 84. Untreated FFRs (n = 3) surpassed the minimum NaCl filtration efficiency, achieving 97.01% (±0.56) as a baseline before treatment. Horizontal dotted lines represent the bacterial filtration efficiency (3 μm droplet size) requirement of ≥98% according to EN 14683 for Type II and ASTM F2100 for Level 2 SMs. Untreated SMs (n = 3) surpassed the minimum BFE, achieving 99.50% (±0.08) as a baseline before treatment.
Fig 5
Fig 5. Surgical mask (SM) breathability testing after single-cycle or multiple-cycle decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Horizontal dotted lines represent the maximum allowed differential pressure in following standards: <40 Pa/cm2 according to EN 14683:2019 Annex C for Type I and II masks and < 60 Pa/cm2 for Type IIR. Untreated SMs (n = 5) achieved 52.08 (±0.99) Pa/cm2 differential pressure as a baseline before treatment.
Fig 6
Fig 6. Filtering facepiece respirator (FFR) breathability testing after single-cycle or multiple-cycle decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Exhalation (A) and inhalation (B) breathing resistances after decontamination. Horizontal dashed (above) and dotted (below) lines represent the following breathing resistance standards: Exhalation: ≤25 mmH2O and Inhalation: ≤35 mmH2O for FFRs according to NIOSH 42 CFR Part 84. Untreated FFRs (n = 5) achieved inhalation and exhalation resistance of 12.43 (±0.69) mmH2O and 11.9 (±0.86) mmH2O, respectively.
Fig 7
Fig 7. Porcine coronavirus (PRCV) inactivation following multiple cycle surgical mask (SM) decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Titrations were performed after two or five (three in the case of DH) decontamination treatments on PRCV-inoculated SM coupons and straps. PRCV infectivity was analysed in swine testicular cells. The cell culture limit of detection (LOD) was 0.80 log10 TCID50/mL (6.31×100 TCID50/mL) for all analyses except those concerning VHP-treated SM straps (1.80 log10 TCID50/mL (6.31×101 TCID50/mL)). Per decontamination method, nine PRCV-inoculated, decontaminated coupons (n = 9) and three inoculated, decontaminated straps (n = 3) were analysed in parallel to inoculated, untreated, positive control (c+) coupons (n = 9) and straps (n = 3). Mean log10 TCID50/mL and standard errors of the means are represented. P-values were computed by using a two-sided independent sample t-test, where ****P<0.0001, ***P<0.001, **P<0.01, *P<0.05, and ns is P≥0.05.
Fig 8
Fig 8. Porcine coronavirus (PRCV) inactivation following multiple cycle filtering facepiece respirator (FFR) decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Titrations were performed after two or five (three in the case of DH) decontamination treatments on PRCV-inoculated FFR coupons and straps. PRCV infectivity was analysed in swine testicular cells. The cell culture limit of detection (LOD) was 0.80 log10 TCID50/mL (6.31×100 TCID50/mL) for all analyses except those concerning VHP-treated FFR straps (1.80 log10 TCID50/mL (6.31×101 TCID50/mL)). Per decontamination method, nine PRCV-inoculated, decontaminated coupons (n = 9) and three inoculated, decontaminated straps (n = 3) were analysed in parallel to inoculated, untreated, positive control (c+) coupons (n = 9) and straps (n = 3). Mean log10 TCID50/mL and standard errors of the means are represented. P-values were computed by using a two-sided independent sample t-test, where ****P<0.0001, ***P<0.001, **P<0.01, *P<0.05, and ns is P≥0.05.
Fig 9
Fig 9. Murine norovirus (MuNoV) inactivation following multiple cycle surgical mask (SM) decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Titrations were performed after two or five (three in the case of DH) decontamination treatments on MuNoV-inoculated SM coupons and straps. MuNoV infectivity was analysed in RAW264.7 cells. The cell culture limit of detection (LOD) was 0.80 log10 TCID50/mL (6.31×100 TCID50/mL) for all analyses except those concerning VHP-treated SM straps (1.80 log10 TCID50/mL (6.31×101 TCID50/mL)). Per decontamination method, nine PRCV-inoculated, decontaminated coupons (n = 9) and three inoculated, decontaminated straps (n = 3) were analysed in parallel to inoculated, untreated, positive control (c+) coupons (n = 9) and straps (n = 3). Mean log10 TCID50/mL and standard errors of the means are represented. P-values were computed by using a two-sided independent sample t-test, where ****P<0.0001, ***P<0.001, **P<0.01, *P<0.05, and ns is P≥0.05.
Fig 10
Fig 10. Murine norovirus (MuNoV) inactivation following multiple cycle filtering facepiece respirator (FFR) decontamination using dry heat (DH), vaporised hydrogen peroxide (VHP), and ultraviolet germicidal irradiation (UVGI).
Titrations were performed after two or five (three in the case of DH) decontamination treatments on MuNoV- inoculated FFR coupons and straps. MuNoV infectivity was analysed in RAW264.7 cells. The cell culture limit of detection (LOD) was 0.80 log10 TCID50/mL (6.31×100 TCID50/mL) for all analyses except those concerning VHP- and UVGI-treated FFR straps (1.80 log10 TCID50/mL (6.31×101 TCID50/mL)). Per decontamination method, nine PRCV-inoculated, decontaminated coupons (n = 9) and three inoculated, decontaminated straps (n = 3) were analysed in parallel to inoculated, untreated, positive control (c+) coupons (n = 9) and straps (n = 3). Mean log10 TCID50/mL and standard errors of the means are represented. P-values were computed by using a two-sided independent sample t-test, where ****P<0.0001, ***P<0.001, **P<0.01, *P<0.05, and ns is P≥0.05.
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This work was supported by a grant from the Walloon Region, Belgium (Project 2010053 -2020- “MASK - Decontamination and reuse of surgical masks and filtering facepiece respirators”) and the ULiège Fonds Spéciaux pour la Recherche 2020. The sponsors did not play a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.