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.
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.
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.
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.
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.
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.
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.
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.
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.
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.