TY - JOUR
AU - Sharan,, Jitendra
AB - Abstract Filtering facepiece respirators (FFRs) are made for one-time use. A massive shortage of FFRs is widespread during pandemic events and has forced many healthcare organizations to decontaminate them and re-use for a limited time. Many decontamination methods have been proposed for the decontamination of FFRs. This review highlights various aspects of decontamination methods available in the literature. Among various methods available, vaporized hydrogen peroxide, ultraviolet irradiation, and dry heat seem to be the most promising decontaminants for FFRs. On the other hand, microwave, bleach, ethylene oxide, alcohol, hydrogen peroxide liquid, sanitizing wipes, and soap and water are not recommended methods for FFR decontamination. decontamination, disinfection, FFR, filtering facepiece respirator, N95 respirator, re-use, respirator, sterilization Introduction The demand for filtering facepiece respirators (FFRs) has been very high during the ongoing COVID-19 pandemic (CDC, 2020a). The Centers for Disease Control and Prevention (CDC) and National Institute for Occupational Safety and Health (NIOSH) do not recommend the re-use of FFRs as a standard measure (CDC, 2020a,b). However, their re-use is considered as a crisis capacity strategy during a massive shortage to ensure continued supply (CDC, 2020b). The protocols for the use and re-use of FFRs are recommended by the CDC, NIOSH, and Occupational Safety and Health Administration (OSHA) (CDC, 2020a). During the ongoing COVID-19 pandemic, CDC has recommended extended use of FFRs up to 8 h and limited re-use up to five times under acceptable circumstances (CDC, 2020a). Many healthcare organizations have begun re-using FFRs. At present, there are no guidelines and recommended methods from the FFRs manufacturer regarding the decontamination of the same except 3M company (3M Company, 2020). Also, to the best of our knowledge, to date, only two reports exist supporting the effectiveness of a few decontamination methods specifically against the SARS-CoV-2 virus on FFRs (Fischer et al., 2020; Ibáñez-Cervantes et al., 2020). This review is intended to highlight the various aspects of currently available decontamination strategies for the re-use of FFRs during the ongoing COVID-19 pandemic. Methods Various strategies for the decontamination of FFRs were assessed in the present review. The following were important aspects of a successful decontamination process: The decontamination method must reduce the pathogen burden. The filtration efficiency of the FFR must remain intact. The fit factor of the FFR must be maintained. The decontamination process must not leave any hazardous chemical residue. The method should be feasible and easy to carry out. The method should decontaminate the FFRs in bulk. The process must be fast and with less contact time. The potentially relevant studies in the English language identified through a literature search of electronic databases such as PubMed, NCBI, and Google Scholar till 20 July 2020. The terms used for the electronic search were: ‘Decontamination’ OR ‘Sterilization’ OR ‘Disinfection’ OR ‘Re-use’ OR ‘Respirator’ OR ‘Filtering Facepiece Respirator’ OR ‘FFR’ OR ‘N95 respirator’ OR ‘N95 FFR’ OR ‘Respiratory Protection Equipment’. The abstract and title of the articles were retrieved from the electronic databases by one of the authors (A.K.J.). Studies included any of the search terms were initially selected, and duplicates were removed. This was followed by the screening of the title, followed by the abstracts. Articles that fall within the scope of the present study were retrieved in full text and included in the review. Along with this, the latest reports, updates, and technical bulletins from major health policy regulatory authorities such as NIOSH, CDC, WHO, and FFR manufacturers were also given considerations in the present review. Results All peer-reviewed and latest publications and guidelines from major health policy regulatory authorities were given priority in the present review. We identified 13 different processes for the decontamination of FFRs and the details are mentioned in Table 1. Table 1. Summary of various decontamination methods on performance of respirators and their antimicrobial efficacy. Decontamination method . Reference . Decontamination protocol . FFR series/ model . Effects on FFR performance . Effect on antimicrobial efficacy . Remarks . . . . . Filtration . Fit . Other . Microbe . Efficacy . . VHP Viscusi et al. (2007) STERRAD NX plasma sterilizer, 59% H2O2, 28 min cycle. STERRAD 100S plasma sterilizer, 58% H2O2, 28 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of nosebands Not tested Not tested FFRs containing cellulose material can absorb H2O2 and may compromise the decontamination. There was no hazardous residues remained on the FFRs. Viscusi et al. (2009) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of metallic nosebands Not tested Not tested FFRs containing cellulose can absorb H2O2 and cause the decontamination cycle to abort due to low H2O2 vapor concentration. Residual vapor off-gassing from the FFR materials are unlikely as the vapors decompose into water vapor and oxygen. Salter et al. (2010) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle at 45–55°C. N95 Not tested Not tested No gas residue found but approx. 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residual oxidants remained on the FFRs, but did not pose health hazard. Bergman et al. (2010) STERRAD 100S plasma sterilizer, 59% H2O2, 55 min cycle at 45–50°C (total three cycles). N95 Filtration efficiency decreased (mean penetration >5%) No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of decontamination were most likely to experience the large degradation of filtration performance. Those FFRs most exposed to processing conditions degraded maximum. FFR stacking order inside the sterilization processing pouches had a significant role in the degradation. Bergman et al. (2010) ClarusR HVP generator, 30% H2O2 at 8 g m−3 room concentration, 15 min dwell and 125 min cycle (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of H2O2 vapor decontamination (not plasma) did not experience large degradation of filtration performance. Battelle report (2016) Bioquell Clarus C HPV generator, 30% H2O2, 10 min conditioning phase, 20 min gassing phase at 2 g min−1, 150-min dwell phase at 0.5 g min−1, and 300 min of aeration. 3M 1860 No effect on filter performance up to 50 treatments No effect on fit up to 20 treatments Degradation of FFR straps after 30 treatments Geobacillus stearothermophilus spores >99.999% The measured H2O2 concentration ‘off-gassing’ from the FFR was below the permissible exposure limit of 1 ppm when the first measurement was done at 210 min. Kenney et al. (2020) Bioquell BQ-50 generator, 10 min conditioning phase, 30–40 min gassing phase at 16 g min−1, 25 min dwell phase and 150 min aeration. 3M 1860 Not tested Not tested After five cycles, the respirators appeared similar to new with no deformity T1, T7, and phi-6 bacteriophages >99.999% VHP was highly effective in killing various bacteriophages that were more resistance than SARS-CoVs. Fischer et al. (2020) Panasonic MCO- 19AIC-PT (PHC Corp., http://www.phchd.com) incubator with VHP generator, ≈1000 ppm H2O2 for 10 min. 3M 9211 No effect on filter performance No effect on fit up to three cycles Not tested SARS-CoV-2 virus <99.9% reduction of viral load VHP yielded extremely rapid inactivation of viruses. Cramer et al. (2020) SteraMist Binary Ionization Technology (BIT), 7.8% aqueous H2O2 aerosol, 0.05–3 µm droplets, 90 ml min−1 for 15 min, 17.7 ml m−3 concentration. 3M 1980, KC/ Holyard 46767, Gerson 2130, 3M 8210 and 3M 9210/37021 No effect on filter performance No effect on fit up to five cycles Not tested Geobacillus stearothermophilus spores At least 99.9999999% reduction of spores Filtration efficiency of FFRs was maintained up to 10 days following one to five cycles of ionized H2O2 decontamination. Jatta et al. (2020) VHP in V-PRO maX low temperature sterilization system, 59% H2O2, 28 min cycle (total 5–10 cycles). 3M 8211 and 3M 9210 No effect on filter performance No effect on fit No effect on odor, face irritation and straps of FFRs Not tested Not tested Higher concentration of H2O2 may be used for better virucidal efficacy. FFRs processed for 15 cycles were reported to be tighter and uncomfortable on the face. Ibáñez- Cervantes et al. (2020) STERRAD 100NX sterilization system, 59% H2O2, 47 min exposure to H2O2 plasma. 3M 8210 Not tested Not tested Not mentioned SARS-CoV-2 virus, Acinetobacter baumannii, and Staphylococcus aureus No detection of any virus and 100% bacterial death Hydrogen peroxide plasma can completely eliminate the pathogens from FFRs. EO Viscusi et al. (2007) 3M Steri-Vac 4XL EO sterilizer at 55°C and 883 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested Darkening of straps Not tested Not tested 3M Steri-Vac 5XL had slightly less degrading effect on filters than 3M Steri-Vac 4XL EO sterilizer. Viscusi et al. (2009) 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested No effect on physical appearance Not tested Not tested Residual EO on FFRs is not believed to be a concern as decontamination process includes a 4 h of aeration to remove residual EO. Salter et al. (2010) Amsco Eagle 3017 EO sterilizer at 54°C and 736.4 mg l−1 100% EO gas, 3 h EO exposure and 12 h aeration. N95 Not tested Not tested Diacetone alcohol and ethylene glycol monoacetate toxins were found on the FFRs Not tested Not tested No residual EO was detected on FFRs. Bergman et al. (2010) Amsco Eagle 3017 EO sterilizer at 55°C and 736.4 mg l−1 100% EO gas, 1 h EO exposure and 12 h aeration (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested UVGI Viscusi et al. (2007) Sterilgard III laminar flow cabinet, 40 W, 254 nm, 0.24 mW cm−2 for 30 and 480 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested It was important to control the duration of UV exposure and irradiation of 2 h could be appropriate for N95 FFRs. Viscusi et al. (2009) Sterilgard III laminar flow cabinet, 40 W UV-C, 0.18–0.20 mW cm−2, 176–181 mJ cm−2 for 15 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested No known health risks to the user were observed. Bergman et al. (2010) XX-40S model, 40 W UV-C, 254 nm, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested Bergman et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect was observed on four consecutive donning. Salter et al. (2010) UV-B, 302 nm, 4.0 mW cm−2 or UV-C, 254 nm, 3.4 mW cm−2 (~2.7 × 105 J m−2) for 1 h. N95 Not tested Not tested No effect on physical appearance Not tested Not tested No residual chemicals observed on FFRs after UV irradiation. Fisher and Shaffer (2011) 40 W UV-C, 254 nm, 38–4707 J m−2 IFM specific. 3M 1860, 3M 1870, 3M 8210, and Kimberly- Clark PFR95-174 Not tested Not tested Not tested MS2 coliphage 99.9% reduction of MS2 coliphase at minimum IMF dose of 1000 J m−2 Minimum IFM dose of 1000 J m−2 was required for 99.9% reduction in viable MS2. Model-specific exposure time was needed to achieve minimum IFM dose which ranged from 2 to 266 min. Viscusi et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor Not tested Not tested No meaningful effect on fit, odor and difficulty in multiple donning was observed. Heimbuch et al. (2011) 40 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 18 kJ m−2 for 15 min. N95 Not tested No effect on fit No sign of physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 influenza virus A dose of 1.8 J cm−2 was sufficient to reduce the virus by factor of 99.99%, however sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Labgard class II, type A2 laminar flow cabinet, 15 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 1.8 J cm−2 for 15 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load UV-C irradiation for 15 min resulted destruction of viruses infectivity but their genetic signature remained. Lindsley et al. (2015) 15 W UV-C, 254 nm, dose 0, 120, 240, 470, or 950 J cm−2 on each side of FFR. 3M 1868, 3M 9210, Gerson 1730, and Kimberly-Clark 46727 Particle penetration increased up to 1.25% at higher dose with little effect on the flow resistance No effect on fit At 950 J cm−2, visible breaks or tears were observed with substantial reduction of strength, however, the dose had minimal effect on the straps Not tested Not tested The upper limit of UVGI exposure during repeated disinfection cycles would be set by the physical degradation of FFR material and not by loss filtration capacity. UVGI could be used for the disinfection of FFRs, but the number of disinfection cycles should depend on the respirator model and the UVGI dose. Mills et al. (2018) UV-C, 254 nm, 0.39 W cm−2, 1 J cm−2 for 1 min. 3M 1860, 3M 1870, 3MVFlex1805, AlphaProtech 695, Gerson 1730, Kimberly- Clark PFR, Moldex 1512, Moldex 1712, Moldex EZ-22, Precept 65-3395, Prestige Ameritech RP88020, Sperian HC-NB095, Sperian HC-NB295F, U.S. Safety AD2N95A and U.S. Safety AD4N95 Not tested Not tested Not tested H1N1 influenza ≥99.9% reduction in influenza viability on facepieces from 12 of 15 FFR models and straps from 7 of 15 FFR models UVGI could be effective for FFR decontamination, however careful consideration is required for FFR model, material type and design. Lin et al. (2018) 6 W UV-A 365 nm, 31.2 mW cm−2 for 1, 2, 5, 10, and 20 min. 6 W UV-C 254 nm, 18.9 mW cm−2 for 1, 2, 5, 10, and 20 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores No bacterial colony after 5 min of UV-C and 20% bacterial colony found after 20 min of UV-A treatment Heimbuch and Harnish (2020) UV-C, 1 J cm−2. 3M 1870 Not tested Not tested Not tested Influenza A (H1N1), Avian influenza A (H5N1), Influenza A (H7N9) A/ Anhui/1/2013, Influenza A (H7N9) A/ Shanghai/1/2013, MERS-CoV, and SARS-CoV 99.9% for all tested viruses Fischer et al. (2020) UV light (260–285 nm). N95 Not tested No effect on fit up to three cycles Not tested SARS-CoV-2 virus Not mentioned Virus inactivation by UV irradiation is a slow process, thus the decontamination process should be long enough to ensure sufficient reduction in virus concentration. Autoclave Viscusi et al. (2007) At 121°C, 15 Psi for 15 and 30 min and air drying for 72 h. N95 and P100 Increased filter penetration Badly affected FFRs were deformed, shrunken, stiff, mottled and softer Not tested Not tested Temperature above 80°C likely to affect the performance of the filter media of FFRs. Lin et al. (2018) At 121°C, 103 kPa for 15 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Autoclave had better biocidal efficacy than ethanol and UV-A. Grinshpun et al. (2020) At 250°F, 15 psi for 30 min and drying cycle of 30 min. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested Partial detachment and deformation of nose foam, partial disintegration of sealing material around nose clip and loss of strap elasticity Not tested Not tested The impact of autoclaving on the integrity of 3M 8210 was more compare to 3M 1870 FFRs. MGS Bergman et al. (2010) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam nose cushion and slight melting of head straps Not tested Not tested Possible sparking was caused by the metallic nosebands. However, no sparking was observed where water basins were placed in the microwave with the FFRs. Bergman et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min /cycle (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Slight separation of the inner foam nose cushion Not tested Not tested Multiple cycles of microwave treatment was not to cause a more pronounced separation of inner foam nose cushion compared with single treatment. Fisher and Shaffer (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 up to three cycles of steam exposure (total 90 s). 3M 1860, 3M 1870, 3M 8120, Cardinal Health, Moldex 2200, and Kimberly- Clark PFR95 No effect on filter performance Not tested Water absorption was model specific (FFRs with hydrophilic materials absorbed more water) MS2 bacteriophage 99.99% effective for inactivating MS2 bacteriophages on FFRs FFRs need extended drying period before re-use. Viscusi et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested No sparking or melting of any components of FFR occurred from microwaving. Heimbuch et al. (2011) Microwave oven, 1250 W irradiation at full power for 2 min. N95 Not tested No effect on fit Slight separation of the foam nose cushion H1N1 influenza virus >99.99% reduction of viable H1N1 virus Sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Microwave oven (Panasonic Corp., Secaucus, NJ, USA), 1250 W, 2450 MHz for 2 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Metal nosebands can generate combustion H5N1 virus >99.99% reduction of viral load MGS for 2 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Pascoe et al. (2020) Industrial-grade 2.45 GHz, 1800 W microwave oven (NE- 1853, Panasonic) for 90 s. Kimberly-Clark N95 FFR No effect on filter performance Not tested Arching of metal nose clip and loss of clip adhesion Staphylococcus aureus >99.9999% reduction Addition of lemon- scented essential oil to the MGS process had no negative impact on filtration function. Thus, it can be added to MGS decontamination process to impact a fresh fragrance on to the FFRs if desired. Zulauf et al. (2020) Microwave oven, 1100 W, 3 min cycle−1. 3M 1860 No effect on filter performance No effect on fit No effect on odor and integrity of strap, foam fittings and nose piece MS2 bacteriophage >99.999 and 90–99.9% reduction on FFR segment and elastic straps, respectively The functionality of the FFRs maintained up to 20 decontamination cycles and there was no water retention by the FFRs following decontamination. MHI Bergman et al. (2010) At 60°C and 80% relative humidity for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam cushion and slight melting of head straps Not tested Not tested Bergman et al. (2011) At 60°C and 80% relative humidity for 15 min (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect on four consecutive donning. Viscusi et al. (2011) At 60°C and 80% relative humidity for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested Straps loosening occurred after repeated donning. Heimbuch et al. (2011) At 65°C for 30 min. N95 Not tested No effect on fit No obvious sign of any physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 virus MHI is the time- intensive method and may be useful for the FFRs in small organizations. Lore et al. (2012) At 65°C and 100% relative humidity for 20 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load MHI for 20 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Dry heat Viscusi et al. (2007) Fisher Isotemp 500 series (Fisher Scientific, Pittsburgh, PA, USA) at 80 and 160°C for 60 min. N95 and P100 Increased filter penetration Badly affected Melting of the FFRs at 160°C after 22 min Not tested Not tested The maximum operating temperature should be 90–100°C. Viscusi et al. (2007) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 26 mW cm−3 for 2 and 4 min. N95 and P100 Filter penetration in N95 FFRs increased slightly by 2 min, whereas increased significantly by 4 min of microwave irradiation Not tested Melting of the aluminum nose piece Not tested Not tested Melting of N95 filter media observed following 4 min of microwave irradiation, thus the temperature should not be above 80°C. Viscusi et al. (2009) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. N95 and P100 No effect on filter performance Not tested Chances of FFR melting Not tested Not tested No known health risks to the users were observed. Lin et al. (2018) Traditional electric rice cooker (TERC) at 149–164°C for 3 min without water. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Dry heat is non corrosive and TERC was found to exhibit a biocidal efficacy that reaches effective sterilization in 3 min. Yim et al. (2020) Thermostat- controlled heating oven (ThermoFisher) at 70°C for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Significant decrease of dipole change density of filters following each heat treatment cycle Not tested Not tested Increase temperature altered the state of trapping/ detrapping of electrons and charge dissipation in the electrets filters leading to increased filter penetration. Pascoe et al. (2020) Laboratory MINI116 incubator (Genlab ltd.) at 70°C for 90 min. Kimberly-Clark N95 FFR No effect on filter performance Not tested Not tested Staphylococcus aureus >99.99% reduction Dry heat at 70°C was a relatively slow method and took 90 min to decrease 99.99% bacteria, and filtration efficiency maintained after three decontamination cycles. Fischer et al. (2020) At 70°C for 30 min. N95 Not tested No effect on fit up to 1–2 cycles Not tested SARS-CoV-2 virus <99.9% reduction Virus inactivation by dry heat is a slow process, the decontamination process should be long enough to ensure that sufficient reduction in virus concentration has been achieved. Bleach Viscusi et al. (2007) 0.525 and 5.25% bleach for 30 min. N95 and P100 Slight increase in the filter penetration Not tested Tarnishing of aluminum nosebands Stiffening of filter media and elastic straps with 5.25% bleach Not tested Not tested Further study using diluted bleach concentration is warranted. Viscusi et al. (2009) 0.6% bleach for 30 min. N95 and P100 No effect on filter performance Not tested Tarnishing of the metal nosebands and discoloration of inner nose cushion Not tested Not tested Irritation to eyes, skin, and respiratory tract, and bleach odor are the known health effects. Salter et al. (2010) 0.6% sodium hypochlorite for 30 min. N95 Not tested Not tested Chlorine residues on FFRs were very less, there was skin irritation and chlorine odor Not tested Not tested Residual chlorine might cause skin irritation. Bergman et al. (2010) 0.6% bleach for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Tarnishing of the metallic nosebands, oxidization of staples and discoloration of inner nose pads Not tested Not tested Not suitable for polypropylene filters. Following air-drying between exposure cycles, all FFRs were dry to the touch and had a characteristic of bleach odor. Lin et al. (2018) 0.4 ml of 0.54, 2.7, and 5.4% bleach for 10 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Sodium hypochlorite (5.4%) even with 10-fold dilution (0.54%) had 100% biocidal effect. Liquid hydrogen peroxide Viscusi et al. (2007) 3 and 6% H2O2 for 30 min. N95 and P100 No effect on filter performance Not tested Fading of label ink on the fabric with 6% H2O2 Not tested Not tested Bergman et al. (2010) 6% H2O2 solution for 30 min (total three cycles). N95 No effect on filter performance Not tested Oxidation of staples on FFRs Not tested Not tested Salter et al. (2010) 3% H2O2 for 30 min. N95 Not tested Not tested Approximately 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residue of oxidants retained by the FFRs but did not pose any health hazard Alcohol Viscusi et al. (2007) 70% isopropyl alcohol for 1 s and 1 min. N95 and P100 Filtration efficiency decreased Not tested Fading of strap ink Not tested Not tested Isopropyl alcohol change the density and/or spatial distribution of the electrets charges in the surface of the polymer fibers. Lin et al. (2018) 95, 80, 70, and 50% ethanol and dried for 10 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores The lowest (68 ± 3%) and highest (89 ± 6%) relative survival was with 80 and 50% ethanol, respectively 50% and 80% ethanol had maximum biocidal efficacy, whereas 95 and 70% ethanol had similar biocidal efficacy. Rapid evaporation of ethanol was responsible for less sporicidal activity. Grinshpun et al. (2020) 70% ethanol for 2 h. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested No physical damage Not tested Not tested The impact of ethanol on the integrity of 3M 8210 was more compared with 3M 1870 N95 FFRs. Fischer et al. (2020) 70% ethanol. N95 Not mentioned Not mentioned Not mentioned SARS-CoV-2 virus Not mentioned Hypochlorite solution wipe Heimbuch et al. (2014) Hype-Wipes (Current Technologies, Inc., Crawfordsville, IN, USA) containing 0.9% hypochlorite. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Selective topical application of a more diluted hypochlorite solution in a wipe form can greatly eliminate the oxidative damage of metal nose piece and might serve as 1-step remedy. Benzalkonium chloride wipe Heimbuch et al. (2014) 504/07065 Respirator Cleaning Wipes (3M Company, St. Paul, MN, USA) containing benzalkonium chloride. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Filtration efficiency remained intact up to two to three decontamination cycle. Dimethyl dioxirane (DMDO) Salter et al. (2010) Each FFR was submerged in 200 ml of DMDO (10% Oxone, 10% acetone, and 5% sodium bicarbonate) for 30 min and then 18 h off-gassing in a clinical fume hood. N95 Not tested Not tested Accumulation of visible white residues of DMDO that were assigned as Oxone Not tested Not tested DMDO was not suitable for the decontamination of FFRs. Soap and water Viscusi et al. (2007) Ivory bar soap, 1 g l−1 for 2 and 20 min. N95 and P100 Filtration efficiency decreased Not tested No visible changes in any FFR Not tested Not tested All decontamination methods involving soap like washing machine and dishwasher may have similar effect. Decontamination method . Reference . Decontamination protocol . FFR series/ model . Effects on FFR performance . Effect on antimicrobial efficacy . Remarks . . . . . Filtration . Fit . Other . Microbe . Efficacy . . VHP Viscusi et al. (2007) STERRAD NX plasma sterilizer, 59% H2O2, 28 min cycle. STERRAD 100S plasma sterilizer, 58% H2O2, 28 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of nosebands Not tested Not tested FFRs containing cellulose material can absorb H2O2 and may compromise the decontamination. There was no hazardous residues remained on the FFRs. Viscusi et al. (2009) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of metallic nosebands Not tested Not tested FFRs containing cellulose can absorb H2O2 and cause the decontamination cycle to abort due to low H2O2 vapor concentration. Residual vapor off-gassing from the FFR materials are unlikely as the vapors decompose into water vapor and oxygen. Salter et al. (2010) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle at 45–55°C. N95 Not tested Not tested No gas residue found but approx. 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residual oxidants remained on the FFRs, but did not pose health hazard. Bergman et al. (2010) STERRAD 100S plasma sterilizer, 59% H2O2, 55 min cycle at 45–50°C (total three cycles). N95 Filtration efficiency decreased (mean penetration >5%) No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of decontamination were most likely to experience the large degradation of filtration performance. Those FFRs most exposed to processing conditions degraded maximum. FFR stacking order inside the sterilization processing pouches had a significant role in the degradation. Bergman et al. (2010) ClarusR HVP generator, 30% H2O2 at 8 g m−3 room concentration, 15 min dwell and 125 min cycle (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of H2O2 vapor decontamination (not plasma) did not experience large degradation of filtration performance. Battelle report (2016) Bioquell Clarus C HPV generator, 30% H2O2, 10 min conditioning phase, 20 min gassing phase at 2 g min−1, 150-min dwell phase at 0.5 g min−1, and 300 min of aeration. 3M 1860 No effect on filter performance up to 50 treatments No effect on fit up to 20 treatments Degradation of FFR straps after 30 treatments Geobacillus stearothermophilus spores >99.999% The measured H2O2 concentration ‘off-gassing’ from the FFR was below the permissible exposure limit of 1 ppm when the first measurement was done at 210 min. Kenney et al. (2020) Bioquell BQ-50 generator, 10 min conditioning phase, 30–40 min gassing phase at 16 g min−1, 25 min dwell phase and 150 min aeration. 3M 1860 Not tested Not tested After five cycles, the respirators appeared similar to new with no deformity T1, T7, and phi-6 bacteriophages >99.999% VHP was highly effective in killing various bacteriophages that were more resistance than SARS-CoVs. Fischer et al. (2020) Panasonic MCO- 19AIC-PT (PHC Corp., http://www.phchd.com) incubator with VHP generator, ≈1000 ppm H2O2 for 10 min. 3M 9211 No effect on filter performance No effect on fit up to three cycles Not tested SARS-CoV-2 virus <99.9% reduction of viral load VHP yielded extremely rapid inactivation of viruses. Cramer et al. (2020) SteraMist Binary Ionization Technology (BIT), 7.8% aqueous H2O2 aerosol, 0.05–3 µm droplets, 90 ml min−1 for 15 min, 17.7 ml m−3 concentration. 3M 1980, KC/ Holyard 46767, Gerson 2130, 3M 8210 and 3M 9210/37021 No effect on filter performance No effect on fit up to five cycles Not tested Geobacillus stearothermophilus spores At least 99.9999999% reduction of spores Filtration efficiency of FFRs was maintained up to 10 days following one to five cycles of ionized H2O2 decontamination. Jatta et al. (2020) VHP in V-PRO maX low temperature sterilization system, 59% H2O2, 28 min cycle (total 5–10 cycles). 3M 8211 and 3M 9210 No effect on filter performance No effect on fit No effect on odor, face irritation and straps of FFRs Not tested Not tested Higher concentration of H2O2 may be used for better virucidal efficacy. FFRs processed for 15 cycles were reported to be tighter and uncomfortable on the face. Ibáñez- Cervantes et al. (2020) STERRAD 100NX sterilization system, 59% H2O2, 47 min exposure to H2O2 plasma. 3M 8210 Not tested Not tested Not mentioned SARS-CoV-2 virus, Acinetobacter baumannii, and Staphylococcus aureus No detection of any virus and 100% bacterial death Hydrogen peroxide plasma can completely eliminate the pathogens from FFRs. EO Viscusi et al. (2007) 3M Steri-Vac 4XL EO sterilizer at 55°C and 883 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested Darkening of straps Not tested Not tested 3M Steri-Vac 5XL had slightly less degrading effect on filters than 3M Steri-Vac 4XL EO sterilizer. Viscusi et al. (2009) 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested No effect on physical appearance Not tested Not tested Residual EO on FFRs is not believed to be a concern as decontamination process includes a 4 h of aeration to remove residual EO. Salter et al. (2010) Amsco Eagle 3017 EO sterilizer at 54°C and 736.4 mg l−1 100% EO gas, 3 h EO exposure and 12 h aeration. N95 Not tested Not tested Diacetone alcohol and ethylene glycol monoacetate toxins were found on the FFRs Not tested Not tested No residual EO was detected on FFRs. Bergman et al. (2010) Amsco Eagle 3017 EO sterilizer at 55°C and 736.4 mg l−1 100% EO gas, 1 h EO exposure and 12 h aeration (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested UVGI Viscusi et al. (2007) Sterilgard III laminar flow cabinet, 40 W, 254 nm, 0.24 mW cm−2 for 30 and 480 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested It was important to control the duration of UV exposure and irradiation of 2 h could be appropriate for N95 FFRs. Viscusi et al. (2009) Sterilgard III laminar flow cabinet, 40 W UV-C, 0.18–0.20 mW cm−2, 176–181 mJ cm−2 for 15 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested No known health risks to the user were observed. Bergman et al. (2010) XX-40S model, 40 W UV-C, 254 nm, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested Bergman et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect was observed on four consecutive donning. Salter et al. (2010) UV-B, 302 nm, 4.0 mW cm−2 or UV-C, 254 nm, 3.4 mW cm−2 (~2.7 × 105 J m−2) for 1 h. N95 Not tested Not tested No effect on physical appearance Not tested Not tested No residual chemicals observed on FFRs after UV irradiation. Fisher and Shaffer (2011) 40 W UV-C, 254 nm, 38–4707 J m−2 IFM specific. 3M 1860, 3M 1870, 3M 8210, and Kimberly- Clark PFR95-174 Not tested Not tested Not tested MS2 coliphage 99.9% reduction of MS2 coliphase at minimum IMF dose of 1000 J m−2 Minimum IFM dose of 1000 J m−2 was required for 99.9% reduction in viable MS2. Model-specific exposure time was needed to achieve minimum IFM dose which ranged from 2 to 266 min. Viscusi et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor Not tested Not tested No meaningful effect on fit, odor and difficulty in multiple donning was observed. Heimbuch et al. (2011) 40 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 18 kJ m−2 for 15 min. N95 Not tested No effect on fit No sign of physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 influenza virus A dose of 1.8 J cm−2 was sufficient to reduce the virus by factor of 99.99%, however sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Labgard class II, type A2 laminar flow cabinet, 15 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 1.8 J cm−2 for 15 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load UV-C irradiation for 15 min resulted destruction of viruses infectivity but their genetic signature remained. Lindsley et al. (2015) 15 W UV-C, 254 nm, dose 0, 120, 240, 470, or 950 J cm−2 on each side of FFR. 3M 1868, 3M 9210, Gerson 1730, and Kimberly-Clark 46727 Particle penetration increased up to 1.25% at higher dose with little effect on the flow resistance No effect on fit At 950 J cm−2, visible breaks or tears were observed with substantial reduction of strength, however, the dose had minimal effect on the straps Not tested Not tested The upper limit of UVGI exposure during repeated disinfection cycles would be set by the physical degradation of FFR material and not by loss filtration capacity. UVGI could be used for the disinfection of FFRs, but the number of disinfection cycles should depend on the respirator model and the UVGI dose. Mills et al. (2018) UV-C, 254 nm, 0.39 W cm−2, 1 J cm−2 for 1 min. 3M 1860, 3M 1870, 3MVFlex1805, AlphaProtech 695, Gerson 1730, Kimberly- Clark PFR, Moldex 1512, Moldex 1712, Moldex EZ-22, Precept 65-3395, Prestige Ameritech RP88020, Sperian HC-NB095, Sperian HC-NB295F, U.S. Safety AD2N95A and U.S. Safety AD4N95 Not tested Not tested Not tested H1N1 influenza ≥99.9% reduction in influenza viability on facepieces from 12 of 15 FFR models and straps from 7 of 15 FFR models UVGI could be effective for FFR decontamination, however careful consideration is required for FFR model, material type and design. Lin et al. (2018) 6 W UV-A 365 nm, 31.2 mW cm−2 for 1, 2, 5, 10, and 20 min. 6 W UV-C 254 nm, 18.9 mW cm−2 for 1, 2, 5, 10, and 20 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores No bacterial colony after 5 min of UV-C and 20% bacterial colony found after 20 min of UV-A treatment Heimbuch and Harnish (2020) UV-C, 1 J cm−2. 3M 1870 Not tested Not tested Not tested Influenza A (H1N1), Avian influenza A (H5N1), Influenza A (H7N9) A/ Anhui/1/2013, Influenza A (H7N9) A/ Shanghai/1/2013, MERS-CoV, and SARS-CoV 99.9% for all tested viruses Fischer et al. (2020) UV light (260–285 nm). N95 Not tested No effect on fit up to three cycles Not tested SARS-CoV-2 virus Not mentioned Virus inactivation by UV irradiation is a slow process, thus the decontamination process should be long enough to ensure sufficient reduction in virus concentration. Autoclave Viscusi et al. (2007) At 121°C, 15 Psi for 15 and 30 min and air drying for 72 h. N95 and P100 Increased filter penetration Badly affected FFRs were deformed, shrunken, stiff, mottled and softer Not tested Not tested Temperature above 80°C likely to affect the performance of the filter media of FFRs. Lin et al. (2018) At 121°C, 103 kPa for 15 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Autoclave had better biocidal efficacy than ethanol and UV-A. Grinshpun et al. (2020) At 250°F, 15 psi for 30 min and drying cycle of 30 min. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested Partial detachment and deformation of nose foam, partial disintegration of sealing material around nose clip and loss of strap elasticity Not tested Not tested The impact of autoclaving on the integrity of 3M 8210 was more compare to 3M 1870 FFRs. MGS Bergman et al. (2010) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam nose cushion and slight melting of head straps Not tested Not tested Possible sparking was caused by the metallic nosebands. However, no sparking was observed where water basins were placed in the microwave with the FFRs. Bergman et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min /cycle (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Slight separation of the inner foam nose cushion Not tested Not tested Multiple cycles of microwave treatment was not to cause a more pronounced separation of inner foam nose cushion compared with single treatment. Fisher and Shaffer (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 up to three cycles of steam exposure (total 90 s). 3M 1860, 3M 1870, 3M 8120, Cardinal Health, Moldex 2200, and Kimberly- Clark PFR95 No effect on filter performance Not tested Water absorption was model specific (FFRs with hydrophilic materials absorbed more water) MS2 bacteriophage 99.99% effective for inactivating MS2 bacteriophages on FFRs FFRs need extended drying period before re-use. Viscusi et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested No sparking or melting of any components of FFR occurred from microwaving. Heimbuch et al. (2011) Microwave oven, 1250 W irradiation at full power for 2 min. N95 Not tested No effect on fit Slight separation of the foam nose cushion H1N1 influenza virus >99.99% reduction of viable H1N1 virus Sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Microwave oven (Panasonic Corp., Secaucus, NJ, USA), 1250 W, 2450 MHz for 2 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Metal nosebands can generate combustion H5N1 virus >99.99% reduction of viral load MGS for 2 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Pascoe et al. (2020) Industrial-grade 2.45 GHz, 1800 W microwave oven (NE- 1853, Panasonic) for 90 s. Kimberly-Clark N95 FFR No effect on filter performance Not tested Arching of metal nose clip and loss of clip adhesion Staphylococcus aureus >99.9999% reduction Addition of lemon- scented essential oil to the MGS process had no negative impact on filtration function. Thus, it can be added to MGS decontamination process to impact a fresh fragrance on to the FFRs if desired. Zulauf et al. (2020) Microwave oven, 1100 W, 3 min cycle−1. 3M 1860 No effect on filter performance No effect on fit No effect on odor and integrity of strap, foam fittings and nose piece MS2 bacteriophage >99.999 and 90–99.9% reduction on FFR segment and elastic straps, respectively The functionality of the FFRs maintained up to 20 decontamination cycles and there was no water retention by the FFRs following decontamination. MHI Bergman et al. (2010) At 60°C and 80% relative humidity for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam cushion and slight melting of head straps Not tested Not tested Bergman et al. (2011) At 60°C and 80% relative humidity for 15 min (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect on four consecutive donning. Viscusi et al. (2011) At 60°C and 80% relative humidity for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested Straps loosening occurred after repeated donning. Heimbuch et al. (2011) At 65°C for 30 min. N95 Not tested No effect on fit No obvious sign of any physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 virus MHI is the time- intensive method and may be useful for the FFRs in small organizations. Lore et al. (2012) At 65°C and 100% relative humidity for 20 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load MHI for 20 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Dry heat Viscusi et al. (2007) Fisher Isotemp 500 series (Fisher Scientific, Pittsburgh, PA, USA) at 80 and 160°C for 60 min. N95 and P100 Increased filter penetration Badly affected Melting of the FFRs at 160°C after 22 min Not tested Not tested The maximum operating temperature should be 90–100°C. Viscusi et al. (2007) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 26 mW cm−3 for 2 and 4 min. N95 and P100 Filter penetration in N95 FFRs increased slightly by 2 min, whereas increased significantly by 4 min of microwave irradiation Not tested Melting of the aluminum nose piece Not tested Not tested Melting of N95 filter media observed following 4 min of microwave irradiation, thus the temperature should not be above 80°C. Viscusi et al. (2009) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. N95 and P100 No effect on filter performance Not tested Chances of FFR melting Not tested Not tested No known health risks to the users were observed. Lin et al. (2018) Traditional electric rice cooker (TERC) at 149–164°C for 3 min without water. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Dry heat is non corrosive and TERC was found to exhibit a biocidal efficacy that reaches effective sterilization in 3 min. Yim et al. (2020) Thermostat- controlled heating oven (ThermoFisher) at 70°C for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Significant decrease of dipole change density of filters following each heat treatment cycle Not tested Not tested Increase temperature altered the state of trapping/ detrapping of electrons and charge dissipation in the electrets filters leading to increased filter penetration. Pascoe et al. (2020) Laboratory MINI116 incubator (Genlab ltd.) at 70°C for 90 min. Kimberly-Clark N95 FFR No effect on filter performance Not tested Not tested Staphylococcus aureus >99.99% reduction Dry heat at 70°C was a relatively slow method and took 90 min to decrease 99.99% bacteria, and filtration efficiency maintained after three decontamination cycles. Fischer et al. (2020) At 70°C for 30 min. N95 Not tested No effect on fit up to 1–2 cycles Not tested SARS-CoV-2 virus <99.9% reduction Virus inactivation by dry heat is a slow process, the decontamination process should be long enough to ensure that sufficient reduction in virus concentration has been achieved. Bleach Viscusi et al. (2007) 0.525 and 5.25% bleach for 30 min. N95 and P100 Slight increase in the filter penetration Not tested Tarnishing of aluminum nosebands Stiffening of filter media and elastic straps with 5.25% bleach Not tested Not tested Further study using diluted bleach concentration is warranted. Viscusi et al. (2009) 0.6% bleach for 30 min. N95 and P100 No effect on filter performance Not tested Tarnishing of the metal nosebands and discoloration of inner nose cushion Not tested Not tested Irritation to eyes, skin, and respiratory tract, and bleach odor are the known health effects. Salter et al. (2010) 0.6% sodium hypochlorite for 30 min. N95 Not tested Not tested Chlorine residues on FFRs were very less, there was skin irritation and chlorine odor Not tested Not tested Residual chlorine might cause skin irritation. Bergman et al. (2010) 0.6% bleach for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Tarnishing of the metallic nosebands, oxidization of staples and discoloration of inner nose pads Not tested Not tested Not suitable for polypropylene filters. Following air-drying between exposure cycles, all FFRs were dry to the touch and had a characteristic of bleach odor. Lin et al. (2018) 0.4 ml of 0.54, 2.7, and 5.4% bleach for 10 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Sodium hypochlorite (5.4%) even with 10-fold dilution (0.54%) had 100% biocidal effect. Liquid hydrogen peroxide Viscusi et al. (2007) 3 and 6% H2O2 for 30 min. N95 and P100 No effect on filter performance Not tested Fading of label ink on the fabric with 6% H2O2 Not tested Not tested Bergman et al. (2010) 6% H2O2 solution for 30 min (total three cycles). N95 No effect on filter performance Not tested Oxidation of staples on FFRs Not tested Not tested Salter et al. (2010) 3% H2O2 for 30 min. N95 Not tested Not tested Approximately 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residue of oxidants retained by the FFRs but did not pose any health hazard Alcohol Viscusi et al. (2007) 70% isopropyl alcohol for 1 s and 1 min. N95 and P100 Filtration efficiency decreased Not tested Fading of strap ink Not tested Not tested Isopropyl alcohol change the density and/or spatial distribution of the electrets charges in the surface of the polymer fibers. Lin et al. (2018) 95, 80, 70, and 50% ethanol and dried for 10 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores The lowest (68 ± 3%) and highest (89 ± 6%) relative survival was with 80 and 50% ethanol, respectively 50% and 80% ethanol had maximum biocidal efficacy, whereas 95 and 70% ethanol had similar biocidal efficacy. Rapid evaporation of ethanol was responsible for less sporicidal activity. Grinshpun et al. (2020) 70% ethanol for 2 h. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested No physical damage Not tested Not tested The impact of ethanol on the integrity of 3M 8210 was more compared with 3M 1870 N95 FFRs. Fischer et al. (2020) 70% ethanol. N95 Not mentioned Not mentioned Not mentioned SARS-CoV-2 virus Not mentioned Hypochlorite solution wipe Heimbuch et al. (2014) Hype-Wipes (Current Technologies, Inc., Crawfordsville, IN, USA) containing 0.9% hypochlorite. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Selective topical application of a more diluted hypochlorite solution in a wipe form can greatly eliminate the oxidative damage of metal nose piece and might serve as 1-step remedy. Benzalkonium chloride wipe Heimbuch et al. (2014) 504/07065 Respirator Cleaning Wipes (3M Company, St. Paul, MN, USA) containing benzalkonium chloride. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Filtration efficiency remained intact up to two to three decontamination cycle. Dimethyl dioxirane (DMDO) Salter et al. (2010) Each FFR was submerged in 200 ml of DMDO (10% Oxone, 10% acetone, and 5% sodium bicarbonate) for 30 min and then 18 h off-gassing in a clinical fume hood. N95 Not tested Not tested Accumulation of visible white residues of DMDO that were assigned as Oxone Not tested Not tested DMDO was not suitable for the decontamination of FFRs. Soap and water Viscusi et al. (2007) Ivory bar soap, 1 g l−1 for 2 and 20 min. N95 and P100 Filtration efficiency decreased Not tested No visible changes in any FFR Not tested Not tested All decontamination methods involving soap like washing machine and dishwasher may have similar effect. Open in new tab Table 1. Summary of various decontamination methods on performance of respirators and their antimicrobial efficacy. Decontamination method . Reference . Decontamination protocol . FFR series/ model . Effects on FFR performance . Effect on antimicrobial efficacy . Remarks . . . . . Filtration . Fit . Other . Microbe . Efficacy . . VHP Viscusi et al. (2007) STERRAD NX plasma sterilizer, 59% H2O2, 28 min cycle. STERRAD 100S plasma sterilizer, 58% H2O2, 28 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of nosebands Not tested Not tested FFRs containing cellulose material can absorb H2O2 and may compromise the decontamination. There was no hazardous residues remained on the FFRs. Viscusi et al. (2009) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of metallic nosebands Not tested Not tested FFRs containing cellulose can absorb H2O2 and cause the decontamination cycle to abort due to low H2O2 vapor concentration. Residual vapor off-gassing from the FFR materials are unlikely as the vapors decompose into water vapor and oxygen. Salter et al. (2010) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle at 45–55°C. N95 Not tested Not tested No gas residue found but approx. 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residual oxidants remained on the FFRs, but did not pose health hazard. Bergman et al. (2010) STERRAD 100S plasma sterilizer, 59% H2O2, 55 min cycle at 45–50°C (total three cycles). N95 Filtration efficiency decreased (mean penetration >5%) No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of decontamination were most likely to experience the large degradation of filtration performance. Those FFRs most exposed to processing conditions degraded maximum. FFR stacking order inside the sterilization processing pouches had a significant role in the degradation. Bergman et al. (2010) ClarusR HVP generator, 30% H2O2 at 8 g m−3 room concentration, 15 min dwell and 125 min cycle (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of H2O2 vapor decontamination (not plasma) did not experience large degradation of filtration performance. Battelle report (2016) Bioquell Clarus C HPV generator, 30% H2O2, 10 min conditioning phase, 20 min gassing phase at 2 g min−1, 150-min dwell phase at 0.5 g min−1, and 300 min of aeration. 3M 1860 No effect on filter performance up to 50 treatments No effect on fit up to 20 treatments Degradation of FFR straps after 30 treatments Geobacillus stearothermophilus spores >99.999% The measured H2O2 concentration ‘off-gassing’ from the FFR was below the permissible exposure limit of 1 ppm when the first measurement was done at 210 min. Kenney et al. (2020) Bioquell BQ-50 generator, 10 min conditioning phase, 30–40 min gassing phase at 16 g min−1, 25 min dwell phase and 150 min aeration. 3M 1860 Not tested Not tested After five cycles, the respirators appeared similar to new with no deformity T1, T7, and phi-6 bacteriophages >99.999% VHP was highly effective in killing various bacteriophages that were more resistance than SARS-CoVs. Fischer et al. (2020) Panasonic MCO- 19AIC-PT (PHC Corp., http://www.phchd.com) incubator with VHP generator, ≈1000 ppm H2O2 for 10 min. 3M 9211 No effect on filter performance No effect on fit up to three cycles Not tested SARS-CoV-2 virus <99.9% reduction of viral load VHP yielded extremely rapid inactivation of viruses. Cramer et al. (2020) SteraMist Binary Ionization Technology (BIT), 7.8% aqueous H2O2 aerosol, 0.05–3 µm droplets, 90 ml min−1 for 15 min, 17.7 ml m−3 concentration. 3M 1980, KC/ Holyard 46767, Gerson 2130, 3M 8210 and 3M 9210/37021 No effect on filter performance No effect on fit up to five cycles Not tested Geobacillus stearothermophilus spores At least 99.9999999% reduction of spores Filtration efficiency of FFRs was maintained up to 10 days following one to five cycles of ionized H2O2 decontamination. Jatta et al. (2020) VHP in V-PRO maX low temperature sterilization system, 59% H2O2, 28 min cycle (total 5–10 cycles). 3M 8211 and 3M 9210 No effect on filter performance No effect on fit No effect on odor, face irritation and straps of FFRs Not tested Not tested Higher concentration of H2O2 may be used for better virucidal efficacy. FFRs processed for 15 cycles were reported to be tighter and uncomfortable on the face. Ibáñez- Cervantes et al. (2020) STERRAD 100NX sterilization system, 59% H2O2, 47 min exposure to H2O2 plasma. 3M 8210 Not tested Not tested Not mentioned SARS-CoV-2 virus, Acinetobacter baumannii, and Staphylococcus aureus No detection of any virus and 100% bacterial death Hydrogen peroxide plasma can completely eliminate the pathogens from FFRs. EO Viscusi et al. (2007) 3M Steri-Vac 4XL EO sterilizer at 55°C and 883 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested Darkening of straps Not tested Not tested 3M Steri-Vac 5XL had slightly less degrading effect on filters than 3M Steri-Vac 4XL EO sterilizer. Viscusi et al. (2009) 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested No effect on physical appearance Not tested Not tested Residual EO on FFRs is not believed to be a concern as decontamination process includes a 4 h of aeration to remove residual EO. Salter et al. (2010) Amsco Eagle 3017 EO sterilizer at 54°C and 736.4 mg l−1 100% EO gas, 3 h EO exposure and 12 h aeration. N95 Not tested Not tested Diacetone alcohol and ethylene glycol monoacetate toxins were found on the FFRs Not tested Not tested No residual EO was detected on FFRs. Bergman et al. (2010) Amsco Eagle 3017 EO sterilizer at 55°C and 736.4 mg l−1 100% EO gas, 1 h EO exposure and 12 h aeration (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested UVGI Viscusi et al. (2007) Sterilgard III laminar flow cabinet, 40 W, 254 nm, 0.24 mW cm−2 for 30 and 480 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested It was important to control the duration of UV exposure and irradiation of 2 h could be appropriate for N95 FFRs. Viscusi et al. (2009) Sterilgard III laminar flow cabinet, 40 W UV-C, 0.18–0.20 mW cm−2, 176–181 mJ cm−2 for 15 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested No known health risks to the user were observed. Bergman et al. (2010) XX-40S model, 40 W UV-C, 254 nm, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested Bergman et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect was observed on four consecutive donning. Salter et al. (2010) UV-B, 302 nm, 4.0 mW cm−2 or UV-C, 254 nm, 3.4 mW cm−2 (~2.7 × 105 J m−2) for 1 h. N95 Not tested Not tested No effect on physical appearance Not tested Not tested No residual chemicals observed on FFRs after UV irradiation. Fisher and Shaffer (2011) 40 W UV-C, 254 nm, 38–4707 J m−2 IFM specific. 3M 1860, 3M 1870, 3M 8210, and Kimberly- Clark PFR95-174 Not tested Not tested Not tested MS2 coliphage 99.9% reduction of MS2 coliphase at minimum IMF dose of 1000 J m−2 Minimum IFM dose of 1000 J m−2 was required for 99.9% reduction in viable MS2. Model-specific exposure time was needed to achieve minimum IFM dose which ranged from 2 to 266 min. Viscusi et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor Not tested Not tested No meaningful effect on fit, odor and difficulty in multiple donning was observed. Heimbuch et al. (2011) 40 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 18 kJ m−2 for 15 min. N95 Not tested No effect on fit No sign of physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 influenza virus A dose of 1.8 J cm−2 was sufficient to reduce the virus by factor of 99.99%, however sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Labgard class II, type A2 laminar flow cabinet, 15 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 1.8 J cm−2 for 15 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load UV-C irradiation for 15 min resulted destruction of viruses infectivity but their genetic signature remained. Lindsley et al. (2015) 15 W UV-C, 254 nm, dose 0, 120, 240, 470, or 950 J cm−2 on each side of FFR. 3M 1868, 3M 9210, Gerson 1730, and Kimberly-Clark 46727 Particle penetration increased up to 1.25% at higher dose with little effect on the flow resistance No effect on fit At 950 J cm−2, visible breaks or tears were observed with substantial reduction of strength, however, the dose had minimal effect on the straps Not tested Not tested The upper limit of UVGI exposure during repeated disinfection cycles would be set by the physical degradation of FFR material and not by loss filtration capacity. UVGI could be used for the disinfection of FFRs, but the number of disinfection cycles should depend on the respirator model and the UVGI dose. Mills et al. (2018) UV-C, 254 nm, 0.39 W cm−2, 1 J cm−2 for 1 min. 3M 1860, 3M 1870, 3MVFlex1805, AlphaProtech 695, Gerson 1730, Kimberly- Clark PFR, Moldex 1512, Moldex 1712, Moldex EZ-22, Precept 65-3395, Prestige Ameritech RP88020, Sperian HC-NB095, Sperian HC-NB295F, U.S. Safety AD2N95A and U.S. Safety AD4N95 Not tested Not tested Not tested H1N1 influenza ≥99.9% reduction in influenza viability on facepieces from 12 of 15 FFR models and straps from 7 of 15 FFR models UVGI could be effective for FFR decontamination, however careful consideration is required for FFR model, material type and design. Lin et al. (2018) 6 W UV-A 365 nm, 31.2 mW cm−2 for 1, 2, 5, 10, and 20 min. 6 W UV-C 254 nm, 18.9 mW cm−2 for 1, 2, 5, 10, and 20 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores No bacterial colony after 5 min of UV-C and 20% bacterial colony found after 20 min of UV-A treatment Heimbuch and Harnish (2020) UV-C, 1 J cm−2. 3M 1870 Not tested Not tested Not tested Influenza A (H1N1), Avian influenza A (H5N1), Influenza A (H7N9) A/ Anhui/1/2013, Influenza A (H7N9) A/ Shanghai/1/2013, MERS-CoV, and SARS-CoV 99.9% for all tested viruses Fischer et al. (2020) UV light (260–285 nm). N95 Not tested No effect on fit up to three cycles Not tested SARS-CoV-2 virus Not mentioned Virus inactivation by UV irradiation is a slow process, thus the decontamination process should be long enough to ensure sufficient reduction in virus concentration. Autoclave Viscusi et al. (2007) At 121°C, 15 Psi for 15 and 30 min and air drying for 72 h. N95 and P100 Increased filter penetration Badly affected FFRs were deformed, shrunken, stiff, mottled and softer Not tested Not tested Temperature above 80°C likely to affect the performance of the filter media of FFRs. Lin et al. (2018) At 121°C, 103 kPa for 15 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Autoclave had better biocidal efficacy than ethanol and UV-A. Grinshpun et al. (2020) At 250°F, 15 psi for 30 min and drying cycle of 30 min. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested Partial detachment and deformation of nose foam, partial disintegration of sealing material around nose clip and loss of strap elasticity Not tested Not tested The impact of autoclaving on the integrity of 3M 8210 was more compare to 3M 1870 FFRs. MGS Bergman et al. (2010) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam nose cushion and slight melting of head straps Not tested Not tested Possible sparking was caused by the metallic nosebands. However, no sparking was observed where water basins were placed in the microwave with the FFRs. Bergman et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min /cycle (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Slight separation of the inner foam nose cushion Not tested Not tested Multiple cycles of microwave treatment was not to cause a more pronounced separation of inner foam nose cushion compared with single treatment. Fisher and Shaffer (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 up to three cycles of steam exposure (total 90 s). 3M 1860, 3M 1870, 3M 8120, Cardinal Health, Moldex 2200, and Kimberly- Clark PFR95 No effect on filter performance Not tested Water absorption was model specific (FFRs with hydrophilic materials absorbed more water) MS2 bacteriophage 99.99% effective for inactivating MS2 bacteriophages on FFRs FFRs need extended drying period before re-use. Viscusi et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested No sparking or melting of any components of FFR occurred from microwaving. Heimbuch et al. (2011) Microwave oven, 1250 W irradiation at full power for 2 min. N95 Not tested No effect on fit Slight separation of the foam nose cushion H1N1 influenza virus >99.99% reduction of viable H1N1 virus Sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Microwave oven (Panasonic Corp., Secaucus, NJ, USA), 1250 W, 2450 MHz for 2 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Metal nosebands can generate combustion H5N1 virus >99.99% reduction of viral load MGS for 2 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Pascoe et al. (2020) Industrial-grade 2.45 GHz, 1800 W microwave oven (NE- 1853, Panasonic) for 90 s. Kimberly-Clark N95 FFR No effect on filter performance Not tested Arching of metal nose clip and loss of clip adhesion Staphylococcus aureus >99.9999% reduction Addition of lemon- scented essential oil to the MGS process had no negative impact on filtration function. Thus, it can be added to MGS decontamination process to impact a fresh fragrance on to the FFRs if desired. Zulauf et al. (2020) Microwave oven, 1100 W, 3 min cycle−1. 3M 1860 No effect on filter performance No effect on fit No effect on odor and integrity of strap, foam fittings and nose piece MS2 bacteriophage >99.999 and 90–99.9% reduction on FFR segment and elastic straps, respectively The functionality of the FFRs maintained up to 20 decontamination cycles and there was no water retention by the FFRs following decontamination. MHI Bergman et al. (2010) At 60°C and 80% relative humidity for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam cushion and slight melting of head straps Not tested Not tested Bergman et al. (2011) At 60°C and 80% relative humidity for 15 min (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect on four consecutive donning. Viscusi et al. (2011) At 60°C and 80% relative humidity for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested Straps loosening occurred after repeated donning. Heimbuch et al. (2011) At 65°C for 30 min. N95 Not tested No effect on fit No obvious sign of any physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 virus MHI is the time- intensive method and may be useful for the FFRs in small organizations. Lore et al. (2012) At 65°C and 100% relative humidity for 20 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load MHI for 20 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Dry heat Viscusi et al. (2007) Fisher Isotemp 500 series (Fisher Scientific, Pittsburgh, PA, USA) at 80 and 160°C for 60 min. N95 and P100 Increased filter penetration Badly affected Melting of the FFRs at 160°C after 22 min Not tested Not tested The maximum operating temperature should be 90–100°C. Viscusi et al. (2007) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 26 mW cm−3 for 2 and 4 min. N95 and P100 Filter penetration in N95 FFRs increased slightly by 2 min, whereas increased significantly by 4 min of microwave irradiation Not tested Melting of the aluminum nose piece Not tested Not tested Melting of N95 filter media observed following 4 min of microwave irradiation, thus the temperature should not be above 80°C. Viscusi et al. (2009) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. N95 and P100 No effect on filter performance Not tested Chances of FFR melting Not tested Not tested No known health risks to the users were observed. Lin et al. (2018) Traditional electric rice cooker (TERC) at 149–164°C for 3 min without water. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Dry heat is non corrosive and TERC was found to exhibit a biocidal efficacy that reaches effective sterilization in 3 min. Yim et al. (2020) Thermostat- controlled heating oven (ThermoFisher) at 70°C for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Significant decrease of dipole change density of filters following each heat treatment cycle Not tested Not tested Increase temperature altered the state of trapping/ detrapping of electrons and charge dissipation in the electrets filters leading to increased filter penetration. Pascoe et al. (2020) Laboratory MINI116 incubator (Genlab ltd.) at 70°C for 90 min. Kimberly-Clark N95 FFR No effect on filter performance Not tested Not tested Staphylococcus aureus >99.99% reduction Dry heat at 70°C was a relatively slow method and took 90 min to decrease 99.99% bacteria, and filtration efficiency maintained after three decontamination cycles. Fischer et al. (2020) At 70°C for 30 min. N95 Not tested No effect on fit up to 1–2 cycles Not tested SARS-CoV-2 virus <99.9% reduction Virus inactivation by dry heat is a slow process, the decontamination process should be long enough to ensure that sufficient reduction in virus concentration has been achieved. Bleach Viscusi et al. (2007) 0.525 and 5.25% bleach for 30 min. N95 and P100 Slight increase in the filter penetration Not tested Tarnishing of aluminum nosebands Stiffening of filter media and elastic straps with 5.25% bleach Not tested Not tested Further study using diluted bleach concentration is warranted. Viscusi et al. (2009) 0.6% bleach for 30 min. N95 and P100 No effect on filter performance Not tested Tarnishing of the metal nosebands and discoloration of inner nose cushion Not tested Not tested Irritation to eyes, skin, and respiratory tract, and bleach odor are the known health effects. Salter et al. (2010) 0.6% sodium hypochlorite for 30 min. N95 Not tested Not tested Chlorine residues on FFRs were very less, there was skin irritation and chlorine odor Not tested Not tested Residual chlorine might cause skin irritation. Bergman et al. (2010) 0.6% bleach for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Tarnishing of the metallic nosebands, oxidization of staples and discoloration of inner nose pads Not tested Not tested Not suitable for polypropylene filters. Following air-drying between exposure cycles, all FFRs were dry to the touch and had a characteristic of bleach odor. Lin et al. (2018) 0.4 ml of 0.54, 2.7, and 5.4% bleach for 10 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Sodium hypochlorite (5.4%) even with 10-fold dilution (0.54%) had 100% biocidal effect. Liquid hydrogen peroxide Viscusi et al. (2007) 3 and 6% H2O2 for 30 min. N95 and P100 No effect on filter performance Not tested Fading of label ink on the fabric with 6% H2O2 Not tested Not tested Bergman et al. (2010) 6% H2O2 solution for 30 min (total three cycles). N95 No effect on filter performance Not tested Oxidation of staples on FFRs Not tested Not tested Salter et al. (2010) 3% H2O2 for 30 min. N95 Not tested Not tested Approximately 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residue of oxidants retained by the FFRs but did not pose any health hazard Alcohol Viscusi et al. (2007) 70% isopropyl alcohol for 1 s and 1 min. N95 and P100 Filtration efficiency decreased Not tested Fading of strap ink Not tested Not tested Isopropyl alcohol change the density and/or spatial distribution of the electrets charges in the surface of the polymer fibers. Lin et al. (2018) 95, 80, 70, and 50% ethanol and dried for 10 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores The lowest (68 ± 3%) and highest (89 ± 6%) relative survival was with 80 and 50% ethanol, respectively 50% and 80% ethanol had maximum biocidal efficacy, whereas 95 and 70% ethanol had similar biocidal efficacy. Rapid evaporation of ethanol was responsible for less sporicidal activity. Grinshpun et al. (2020) 70% ethanol for 2 h. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested No physical damage Not tested Not tested The impact of ethanol on the integrity of 3M 8210 was more compared with 3M 1870 N95 FFRs. Fischer et al. (2020) 70% ethanol. N95 Not mentioned Not mentioned Not mentioned SARS-CoV-2 virus Not mentioned Hypochlorite solution wipe Heimbuch et al. (2014) Hype-Wipes (Current Technologies, Inc., Crawfordsville, IN, USA) containing 0.9% hypochlorite. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Selective topical application of a more diluted hypochlorite solution in a wipe form can greatly eliminate the oxidative damage of metal nose piece and might serve as 1-step remedy. Benzalkonium chloride wipe Heimbuch et al. (2014) 504/07065 Respirator Cleaning Wipes (3M Company, St. Paul, MN, USA) containing benzalkonium chloride. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Filtration efficiency remained intact up to two to three decontamination cycle. Dimethyl dioxirane (DMDO) Salter et al. (2010) Each FFR was submerged in 200 ml of DMDO (10% Oxone, 10% acetone, and 5% sodium bicarbonate) for 30 min and then 18 h off-gassing in a clinical fume hood. N95 Not tested Not tested Accumulation of visible white residues of DMDO that were assigned as Oxone Not tested Not tested DMDO was not suitable for the decontamination of FFRs. Soap and water Viscusi et al. (2007) Ivory bar soap, 1 g l−1 for 2 and 20 min. N95 and P100 Filtration efficiency decreased Not tested No visible changes in any FFR Not tested Not tested All decontamination methods involving soap like washing machine and dishwasher may have similar effect. Decontamination method . Reference . Decontamination protocol . FFR series/ model . Effects on FFR performance . Effect on antimicrobial efficacy . Remarks . . . . . Filtration . Fit . Other . Microbe . Efficacy . . VHP Viscusi et al. (2007) STERRAD NX plasma sterilizer, 59% H2O2, 28 min cycle. STERRAD 100S plasma sterilizer, 58% H2O2, 28 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of nosebands Not tested Not tested FFRs containing cellulose material can absorb H2O2 and may compromise the decontamination. There was no hazardous residues remained on the FFRs. Viscusi et al. (2009) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle. N95 and P100 No effect on filter performance Not tested Tarnishing of metallic nosebands Not tested Not tested FFRs containing cellulose can absorb H2O2 and cause the decontamination cycle to abort due to low H2O2 vapor concentration. Residual vapor off-gassing from the FFR materials are unlikely as the vapors decompose into water vapor and oxygen. Salter et al. (2010) STERRAD 100S plasma sterilizer, 58% H2O2, 55 min cycle at 45–55°C. N95 Not tested Not tested No gas residue found but approx. 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residual oxidants remained on the FFRs, but did not pose health hazard. Bergman et al. (2010) STERRAD 100S plasma sterilizer, 59% H2O2, 55 min cycle at 45–50°C (total three cycles). N95 Filtration efficiency decreased (mean penetration >5%) No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of decontamination were most likely to experience the large degradation of filtration performance. Those FFRs most exposed to processing conditions degraded maximum. FFR stacking order inside the sterilization processing pouches had a significant role in the degradation. Bergman et al. (2010) ClarusR HVP generator, 30% H2O2 at 8 g m−3 room concentration, 15 min dwell and 125 min cycle (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested FFRs that received three cycles of H2O2 vapor decontamination (not plasma) did not experience large degradation of filtration performance. Battelle report (2016) Bioquell Clarus C HPV generator, 30% H2O2, 10 min conditioning phase, 20 min gassing phase at 2 g min−1, 150-min dwell phase at 0.5 g min−1, and 300 min of aeration. 3M 1860 No effect on filter performance up to 50 treatments No effect on fit up to 20 treatments Degradation of FFR straps after 30 treatments Geobacillus stearothermophilus spores >99.999% The measured H2O2 concentration ‘off-gassing’ from the FFR was below the permissible exposure limit of 1 ppm when the first measurement was done at 210 min. Kenney et al. (2020) Bioquell BQ-50 generator, 10 min conditioning phase, 30–40 min gassing phase at 16 g min−1, 25 min dwell phase and 150 min aeration. 3M 1860 Not tested Not tested After five cycles, the respirators appeared similar to new with no deformity T1, T7, and phi-6 bacteriophages >99.999% VHP was highly effective in killing various bacteriophages that were more resistance than SARS-CoVs. Fischer et al. (2020) Panasonic MCO- 19AIC-PT (PHC Corp., http://www.phchd.com) incubator with VHP generator, ≈1000 ppm H2O2 for 10 min. 3M 9211 No effect on filter performance No effect on fit up to three cycles Not tested SARS-CoV-2 virus <99.9% reduction of viral load VHP yielded extremely rapid inactivation of viruses. Cramer et al. (2020) SteraMist Binary Ionization Technology (BIT), 7.8% aqueous H2O2 aerosol, 0.05–3 µm droplets, 90 ml min−1 for 15 min, 17.7 ml m−3 concentration. 3M 1980, KC/ Holyard 46767, Gerson 2130, 3M 8210 and 3M 9210/37021 No effect on filter performance No effect on fit up to five cycles Not tested Geobacillus stearothermophilus spores At least 99.9999999% reduction of spores Filtration efficiency of FFRs was maintained up to 10 days following one to five cycles of ionized H2O2 decontamination. Jatta et al. (2020) VHP in V-PRO maX low temperature sterilization system, 59% H2O2, 28 min cycle (total 5–10 cycles). 3M 8211 and 3M 9210 No effect on filter performance No effect on fit No effect on odor, face irritation and straps of FFRs Not tested Not tested Higher concentration of H2O2 may be used for better virucidal efficacy. FFRs processed for 15 cycles were reported to be tighter and uncomfortable on the face. Ibáñez- Cervantes et al. (2020) STERRAD 100NX sterilization system, 59% H2O2, 47 min exposure to H2O2 plasma. 3M 8210 Not tested Not tested Not mentioned SARS-CoV-2 virus, Acinetobacter baumannii, and Staphylococcus aureus No detection of any virus and 100% bacterial death Hydrogen peroxide plasma can completely eliminate the pathogens from FFRs. EO Viscusi et al. (2007) 3M Steri-Vac 4XL EO sterilizer at 55°C and 883 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested Darkening of straps Not tested Not tested 3M Steri-Vac 5XL had slightly less degrading effect on filters than 3M Steri-Vac 4XL EO sterilizer. Viscusi et al. (2009) 3M Steri-Vac 5XL EO sterilizer at 55°C and 725 mg l−1 100% EO gas, 1 h EO exposure and 4 h aeration. N95 and P100 No effect on filter performance Not tested No effect on physical appearance Not tested Not tested Residual EO on FFRs is not believed to be a concern as decontamination process includes a 4 h of aeration to remove residual EO. Salter et al. (2010) Amsco Eagle 3017 EO sterilizer at 54°C and 736.4 mg l−1 100% EO gas, 3 h EO exposure and 12 h aeration. N95 Not tested Not tested Diacetone alcohol and ethylene glycol monoacetate toxins were found on the FFRs Not tested Not tested No residual EO was detected on FFRs. Bergman et al. (2010) Amsco Eagle 3017 EO sterilizer at 55°C and 736.4 mg l−1 100% EO gas, 1 h EO exposure and 12 h aeration (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical changes Not tested Not tested UVGI Viscusi et al. (2007) Sterilgard III laminar flow cabinet, 40 W, 254 nm, 0.24 mW cm−2 for 30 and 480 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested It was important to control the duration of UV exposure and irradiation of 2 h could be appropriate for N95 FFRs. Viscusi et al. (2009) Sterilgard III laminar flow cabinet, 40 W UV-C, 0.18–0.20 mW cm−2, 176–181 mJ cm−2 for 15 min. N95 and P100 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested No known health risks to the user were observed. Bergman et al. (2010) XX-40S model, 40 W UV-C, 254 nm, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit No effect on physical appearance Not tested Not tested Bergman et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 15 min cycle−1 (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect was observed on four consecutive donning. Salter et al. (2010) UV-B, 302 nm, 4.0 mW cm−2 or UV-C, 254 nm, 3.4 mW cm−2 (~2.7 × 105 J m−2) for 1 h. N95 Not tested Not tested No effect on physical appearance Not tested Not tested No residual chemicals observed on FFRs after UV irradiation. Fisher and Shaffer (2011) 40 W UV-C, 254 nm, 38–4707 J m−2 IFM specific. 3M 1860, 3M 1870, 3M 8210, and Kimberly- Clark PFR95-174 Not tested Not tested Not tested MS2 coliphage 99.9% reduction of MS2 coliphase at minimum IMF dose of 1000 J m−2 Minimum IFM dose of 1000 J m−2 was required for 99.9% reduction in viable MS2. Model-specific exposure time was needed to achieve minimum IFM dose which ranged from 2 to 266 min. Viscusi et al. (2011) Sterilgard III laminar flow cabinet, 40 W UV-C, 1.8 mW cm−2 for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor Not tested Not tested No meaningful effect on fit, odor and difficulty in multiple donning was observed. Heimbuch et al. (2011) 40 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 18 kJ m−2 for 15 min. N95 Not tested No effect on fit No sign of physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 influenza virus A dose of 1.8 J cm−2 was sufficient to reduce the virus by factor of 99.99%, however sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Labgard class II, type A2 laminar flow cabinet, 15 W UV-C, 254 nm, 1.6–2.2 mW cm−2, 1.8 J cm−2 for 15 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load UV-C irradiation for 15 min resulted destruction of viruses infectivity but their genetic signature remained. Lindsley et al. (2015) 15 W UV-C, 254 nm, dose 0, 120, 240, 470, or 950 J cm−2 on each side of FFR. 3M 1868, 3M 9210, Gerson 1730, and Kimberly-Clark 46727 Particle penetration increased up to 1.25% at higher dose with little effect on the flow resistance No effect on fit At 950 J cm−2, visible breaks or tears were observed with substantial reduction of strength, however, the dose had minimal effect on the straps Not tested Not tested The upper limit of UVGI exposure during repeated disinfection cycles would be set by the physical degradation of FFR material and not by loss filtration capacity. UVGI could be used for the disinfection of FFRs, but the number of disinfection cycles should depend on the respirator model and the UVGI dose. Mills et al. (2018) UV-C, 254 nm, 0.39 W cm−2, 1 J cm−2 for 1 min. 3M 1860, 3M 1870, 3MVFlex1805, AlphaProtech 695, Gerson 1730, Kimberly- Clark PFR, Moldex 1512, Moldex 1712, Moldex EZ-22, Precept 65-3395, Prestige Ameritech RP88020, Sperian HC-NB095, Sperian HC-NB295F, U.S. Safety AD2N95A and U.S. Safety AD4N95 Not tested Not tested Not tested H1N1 influenza ≥99.9% reduction in influenza viability on facepieces from 12 of 15 FFR models and straps from 7 of 15 FFR models UVGI could be effective for FFR decontamination, however careful consideration is required for FFR model, material type and design. Lin et al. (2018) 6 W UV-A 365 nm, 31.2 mW cm−2 for 1, 2, 5, 10, and 20 min. 6 W UV-C 254 nm, 18.9 mW cm−2 for 1, 2, 5, 10, and 20 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores No bacterial colony after 5 min of UV-C and 20% bacterial colony found after 20 min of UV-A treatment Heimbuch and Harnish (2020) UV-C, 1 J cm−2. 3M 1870 Not tested Not tested Not tested Influenza A (H1N1), Avian influenza A (H5N1), Influenza A (H7N9) A/ Anhui/1/2013, Influenza A (H7N9) A/ Shanghai/1/2013, MERS-CoV, and SARS-CoV 99.9% for all tested viruses Fischer et al. (2020) UV light (260–285 nm). N95 Not tested No effect on fit up to three cycles Not tested SARS-CoV-2 virus Not mentioned Virus inactivation by UV irradiation is a slow process, thus the decontamination process should be long enough to ensure sufficient reduction in virus concentration. Autoclave Viscusi et al. (2007) At 121°C, 15 Psi for 15 and 30 min and air drying for 72 h. N95 and P100 Increased filter penetration Badly affected FFRs were deformed, shrunken, stiff, mottled and softer Not tested Not tested Temperature above 80°C likely to affect the performance of the filter media of FFRs. Lin et al. (2018) At 121°C, 103 kPa for 15 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Autoclave had better biocidal efficacy than ethanol and UV-A. Grinshpun et al. (2020) At 250°F, 15 psi for 30 min and drying cycle of 30 min. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested Partial detachment and deformation of nose foam, partial disintegration of sealing material around nose clip and loss of strap elasticity Not tested Not tested The impact of autoclaving on the integrity of 3M 8210 was more compare to 3M 1870 FFRs. MGS Bergman et al. (2010) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min cycle−1 (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam nose cushion and slight melting of head straps Not tested Not tested Possible sparking was caused by the metallic nosebands. However, no sparking was observed where water basins were placed in the microwave with the FFRs. Bergman et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min /cycle (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Slight separation of the inner foam nose cushion Not tested Not tested Multiple cycles of microwave treatment was not to cause a more pronounced separation of inner foam nose cushion compared with single treatment. Fisher and Shaffer (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 up to three cycles of steam exposure (total 90 s). 3M 1860, 3M 1870, 3M 8120, Cardinal Health, Moldex 2200, and Kimberly- Clark PFR95 No effect on filter performance Not tested Water absorption was model specific (FFRs with hydrophilic materials absorbed more water) MS2 bacteriophage 99.99% effective for inactivating MS2 bacteriophages on FFRs FFRs need extended drying period before re-use. Viscusi et al. (2011) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested No sparking or melting of any components of FFR occurred from microwaving. Heimbuch et al. (2011) Microwave oven, 1250 W irradiation at full power for 2 min. N95 Not tested No effect on fit Slight separation of the foam nose cushion H1N1 influenza virus >99.99% reduction of viable H1N1 virus Sporadic viable viruses were detected after decontamination process. Lore et al. (2012) Microwave oven (Panasonic Corp., Secaucus, NJ, USA), 1250 W, 2450 MHz for 2 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Metal nosebands can generate combustion H5N1 virus >99.99% reduction of viral load MGS for 2 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Pascoe et al. (2020) Industrial-grade 2.45 GHz, 1800 W microwave oven (NE- 1853, Panasonic) for 90 s. Kimberly-Clark N95 FFR No effect on filter performance Not tested Arching of metal nose clip and loss of clip adhesion Staphylococcus aureus >99.9999% reduction Addition of lemon- scented essential oil to the MGS process had no negative impact on filtration function. Thus, it can be added to MGS decontamination process to impact a fresh fragrance on to the FFRs if desired. Zulauf et al. (2020) Microwave oven, 1100 W, 3 min cycle−1. 3M 1860 No effect on filter performance No effect on fit No effect on odor and integrity of strap, foam fittings and nose piece MS2 bacteriophage >99.999 and 90–99.9% reduction on FFR segment and elastic straps, respectively The functionality of the FFRs maintained up to 20 decontamination cycles and there was no water retention by the FFRs following decontamination. MHI Bergman et al. (2010) At 60°C and 80% relative humidity for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Partial separation of inner foam cushion and slight melting of head straps Not tested Not tested Bergman et al. (2011) At 60°C and 80% relative humidity for 15 min (total three cycles). 3M 1860, 3M 1870, and KC PFR95-270 Not tested No effect on fit Not mentioned Not tested Not tested No effect on four consecutive donning. Viscusi et al. (2011) At 60°C and 80% relative humidity for 30 min. 3M 1860, 3M 1870, 3M 8000, 3M 8210, KC PFR95, and Moldex 2200 No effect on filter performance No effect on fit No effect on odor or donning difficulty A slight separation of the inner foam nose cushion Not tested Not tested Straps loosening occurred after repeated donning. Heimbuch et al. (2011) At 65°C for 30 min. N95 Not tested No effect on fit No obvious sign of any physical deformation H1N1 influenza virus >99.99% reduction of viable H1N1 virus MHI is the time- intensive method and may be useful for the FFRs in small organizations. Lore et al. (2012) At 65°C and 100% relative humidity for 20 min. 3M 1860 and 3M 1870 No effect on filter performance Not tested Not tested H5N1 virus >99.99% median reduction of virus load MHI for 20 min resulted inactivation of viruses but their genetic material remained amplifiable following the decontamination treatment. Dry heat Viscusi et al. (2007) Fisher Isotemp 500 series (Fisher Scientific, Pittsburgh, PA, USA) at 80 and 160°C for 60 min. N95 and P100 Increased filter penetration Badly affected Melting of the FFRs at 160°C after 22 min Not tested Not tested The maximum operating temperature should be 90–100°C. Viscusi et al. (2007) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 26 mW cm−3 for 2 and 4 min. N95 and P100 Filter penetration in N95 FFRs increased slightly by 2 min, whereas increased significantly by 4 min of microwave irradiation Not tested Melting of the aluminum nose piece Not tested Not tested Melting of N95 filter media observed following 4 min of microwave irradiation, thus the temperature should not be above 80°C. Viscusi et al. (2009) Microwave oven (R-305KS, Sharp Electronics, Mahwah, NJ, USA), 2450 MHz, 1100 W, 750 W ft−3 for 2 min. N95 and P100 No effect on filter performance Not tested Chances of FFR melting Not tested Not tested No known health risks to the users were observed. Lin et al. (2018) Traditional electric rice cooker (TERC) at 149–164°C for 3 min without water. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Dry heat is non corrosive and TERC was found to exhibit a biocidal efficacy that reaches effective sterilization in 3 min. Yim et al. (2020) Thermostat- controlled heating oven (ThermoFisher) at 70°C for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Significant decrease of dipole change density of filters following each heat treatment cycle Not tested Not tested Increase temperature altered the state of trapping/ detrapping of electrons and charge dissipation in the electrets filters leading to increased filter penetration. Pascoe et al. (2020) Laboratory MINI116 incubator (Genlab ltd.) at 70°C for 90 min. Kimberly-Clark N95 FFR No effect on filter performance Not tested Not tested Staphylococcus aureus >99.99% reduction Dry heat at 70°C was a relatively slow method and took 90 min to decrease 99.99% bacteria, and filtration efficiency maintained after three decontamination cycles. Fischer et al. (2020) At 70°C for 30 min. N95 Not tested No effect on fit up to 1–2 cycles Not tested SARS-CoV-2 virus <99.9% reduction Virus inactivation by dry heat is a slow process, the decontamination process should be long enough to ensure that sufficient reduction in virus concentration has been achieved. Bleach Viscusi et al. (2007) 0.525 and 5.25% bleach for 30 min. N95 and P100 Slight increase in the filter penetration Not tested Tarnishing of aluminum nosebands Stiffening of filter media and elastic straps with 5.25% bleach Not tested Not tested Further study using diluted bleach concentration is warranted. Viscusi et al. (2009) 0.6% bleach for 30 min. N95 and P100 No effect on filter performance Not tested Tarnishing of the metal nosebands and discoloration of inner nose cushion Not tested Not tested Irritation to eyes, skin, and respiratory tract, and bleach odor are the known health effects. Salter et al. (2010) 0.6% sodium hypochlorite for 30 min. N95 Not tested Not tested Chlorine residues on FFRs were very less, there was skin irritation and chlorine odor Not tested Not tested Residual chlorine might cause skin irritation. Bergman et al. (2010) 0.6% bleach for 30 min (total three cycles). N95 No effect on filter performance No effect on fit Tarnishing of the metallic nosebands, oxidization of staples and discoloration of inner nose pads Not tested Not tested Not suitable for polypropylene filters. Following air-drying between exposure cycles, all FFRs were dry to the touch and had a characteristic of bleach odor. Lin et al. (2018) 0.4 ml of 0.54, 2.7, and 5.4% bleach for 10 min. 3M 8210 No effect on filter performance Not tested Not tested Bacillus subtilis spores 99–100% biocidal efficacy Sodium hypochlorite (5.4%) even with 10-fold dilution (0.54%) had 100% biocidal effect. Liquid hydrogen peroxide Viscusi et al. (2007) 3 and 6% H2O2 for 30 min. N95 and P100 No effect on filter performance Not tested Fading of label ink on the fabric with 6% H2O2 Not tested Not tested Bergman et al. (2010) 6% H2O2 solution for 30 min (total three cycles). N95 No effect on filter performance Not tested Oxidation of staples on FFRs Not tested Not tested Salter et al. (2010) 3% H2O2 for 30 min. N95 Not tested Not tested Approximately 1 mg of oxidant residue remained on the FFRs Not tested Not tested Residue of oxidants retained by the FFRs but did not pose any health hazard Alcohol Viscusi et al. (2007) 70% isopropyl alcohol for 1 s and 1 min. N95 and P100 Filtration efficiency decreased Not tested Fading of strap ink Not tested Not tested Isopropyl alcohol change the density and/or spatial distribution of the electrets charges in the surface of the polymer fibers. Lin et al. (2018) 95, 80, 70, and 50% ethanol and dried for 10 min. N95 No effect on filter performance Not tested Not tested Bacillus subtilis spores The lowest (68 ± 3%) and highest (89 ± 6%) relative survival was with 80 and 50% ethanol, respectively 50% and 80% ethanol had maximum biocidal efficacy, whereas 95 and 70% ethanol had similar biocidal efficacy. Rapid evaporation of ethanol was responsible for less sporicidal activity. Grinshpun et al. (2020) 70% ethanol for 2 h. 3M 8210 and 3M 1870 Filtration efficiency decreased Not tested No physical damage Not tested Not tested The impact of ethanol on the integrity of 3M 8210 was more compared with 3M 1870 N95 FFRs. Fischer et al. (2020) 70% ethanol. N95 Not mentioned Not mentioned Not mentioned SARS-CoV-2 virus Not mentioned Hypochlorite solution wipe Heimbuch et al. (2014) Hype-Wipes (Current Technologies, Inc., Crawfordsville, IN, USA) containing 0.9% hypochlorite. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Selective topical application of a more diluted hypochlorite solution in a wipe form can greatly eliminate the oxidative damage of metal nose piece and might serve as 1-step remedy. Benzalkonium chloride wipe Heimbuch et al. (2014) 504/07065 Respirator Cleaning Wipes (3M Company, St. Paul, MN, USA) containing benzalkonium chloride. 3M 1860, 3M 1870, and Kimberly-Clarke PFR No effect on filter performance Not tested Not tested Staphylococcus aureus 99.9–99.999% attenuation Filtration efficiency remained intact up to two to three decontamination cycle. Dimethyl dioxirane (DMDO) Salter et al. (2010) Each FFR was submerged in 200 ml of DMDO (10% Oxone, 10% acetone, and 5% sodium bicarbonate) for 30 min and then 18 h off-gassing in a clinical fume hood. N95 Not tested Not tested Accumulation of visible white residues of DMDO that were assigned as Oxone Not tested Not tested DMDO was not suitable for the decontamination of FFRs. Soap and water Viscusi et al. (2007) Ivory bar soap, 1 g l−1 for 2 and 20 min. N95 and P100 Filtration efficiency decreased Not tested No visible changes in any FFR Not tested Not tested All decontamination methods involving soap like washing machine and dishwasher may have similar effect. Open in new tab Vaporized hydrogen peroxide Vaporized hydrogen peroxide (VHP) is a commonly used broad-spectrum antimicrobial in healthcare organizations. It is produced by the vaporization of liquid hydrogen peroxide at 120°C (McDonnell, 2009). Because of rapid efficacy, compatibility for heat sensitive items, and limited toxicity, VHP is a very popular alternative to other chemical and physical decontamination processes (McDonnell, 2009). The biocidal effect of VHP is due to oxidation of proteins, nucleic acid, and lipids of various molecules leading to the disruption of many structures of microorganism and loss of viability (McDonnell, 2009). In hydrogen peroxide plasma sterilizer, gas plasma is created by using radiofrequency or microwave energy to excite the hydrogen peroxide vapor molecules to generate charged particles. The biocidal effect of hydrogen peroxide in the plasma sterilization is because of these charged particles, which remain in the form of free radicals and react with various cell components of microorganisms such as enzymes and nucleic acid and alter their metabolism (CDC, 2008a). VHP allows multiple cycles of FFR decontamination without altering their filtration efficiency (Viscusi et al., 2007, 2009; Battelle report, 2016; Cramer et al., 2020; Fischer et al., 2020; Jatta et al., 2020) and fit factor (Bergman et al., 2010; Battelle report, 2016; Cramer et al., 2020; Fischer et al., 2020; Jatta et al., 2020). Recently, the Food and Drug Administration (FDA) has also approved VHP as an emergency method for the decontamination of FFRs for healthcare personnel during the ongoing COVID-19 pandemic (FDA, 2020a). VHP is ‘incompatible’ with FFRs containing cellulose (FDA, 2020a). The presence of cellulose in a few brands of FFRs may absorb hydrogen peroxide and the absorbed hydrogen peroxide can degrade the cellulose thus compromising their resistance to degradation (FDA, 2020a). Also FFRs containing cellulose can absorb H2O2 and cause the decontamination cycle to abort due to low H2O2 vapor concentration (Viscusi et al., 2009). Thus, the selection of a suitable FFR for the decontamination by VHP is important. The residual vapor off-gassing from the FFR materials are unlikely as the vapors decompose into water vapor and oxygen (Viscusi et al., 2009). The latest Battelle report (2016) highlighted that the measured H2O2 concentration ‘off-gassing’ from the FFR was below the permissible exposure limit of 1 ppm when the first measurement was made at 210 min. The antimicrobial efficacy of VHP is promising against Geobacillus stearothermophilus spores (>99.999%, Battelle report, 2016; 99.9999999%, Cramer et al., 2020), T1, T7, and phi-6 bacteriophages (>99.999%, Kenney et al., 2020), SARS-CoV-2 viruses (<99.9%, Fischer et al., 2020; 100%, Ibáñez-Cervantes et al., 2020), Acinetobacter baumannii (100%, Ibáñez-Cervantes et al., 2020), and Staphylococcus aureus (100%, Ibáñez-Cervantes et al., 2020). According to the CDC (2020b), VHP machines like the ClarusR R HVP generator may be compatible with FFR decontamination. STERRAD, STERIS, and Battelle VHP sterilizers have also been approved by the FDA (2020b) for the decontamination of FFRs. One study found the presence of oxidant residue on FFRs decontaminated with 58% H2O2, but the authors concluded that this posed no health hazard (Salter et al., 2010). Two studies reported the tarnishing of nosebands (Viscusi et al., 2007, 2009). A Battelle (2016) report revealed degradation of the FFR straps after 30 cycles of VHP decontamination. One study observed no effect on physical changes (Bergman et al., 2010). Recently ionized hydrogen peroxide (iHP) mist has been used for surface disinfection (Tomimist, 2020). iHP has shown to kill bacteria and inactivate viruses thus reduces the risk of exposure from pathogens on treated surfaces (Tomimist, 2020). Cramer et al. (2020) applied this technology for the decontamination of FFRs and observed very high antimicrobial efficacy (at least 99.9999999%). The filtration performance and fit factors of FFRs were maintained for up to five decontamination cycles. Overall, we conclude that VHP is an effective decontaminant that allows for the decontamination of a large number of FFRs at once. The filtration performance and fit factors of FFRs are maintained after multiple decontamination cycles. Tarnishing of the metallic nosebands is a minor side effect of this method, but unavailability of FDA-approved VHP machines in all healthcare settings are the major limitations of this method. Ethylene oxide The ethylene oxide (EO) is a highly reactive and diffusible toxic gas. The biocidal activity of EO is due to its powerful alkylation reaction with various cellular components like enzymes and nucleic acid of microorganisms. It binds to the sulfhydryl and hydroxyl, amino and carboxyl groups, and prevents normal cellular metabolism and ability to reproduce (Phillips and Miller, 1973). At present, there are limited studies evaluating the effect of EO on FFRs (Viscusi et al., 2007, 2009; Bergman et al., 2010; Salter et al., 2010). Three studies (Viscusi et al., 2007, 2009; Bergman et al., 2010) reported EO has no effect on filter performance, and one study (Bergman et al., 2010) reported that it has no effect on the fit of FFRs. It also has no effect on the visible physical changes to the appearance of FFRs (Viscusi et al., 2009; Bergman et al., 2010). The major concern of this decontamination method is the long aeration cycle required for complete removal of EO gas and the presence of residual EO gas, if any. One study found that 4 h of aeration was sufficient for the removal of residual EO gas (Viscusi et al., 2009). Another study found no residue of EO after 12 h of aeration, but they observed the presence of two harmful toxins i.e. diacetone alcohol and ethylene glycol monoacetate on the FFRs (Salter et al., 2010). There is no information related to the antimicrobial efficacy of EO on the FFRs. Although EO is a promising and commonly used sterilant in many healthcare organizations, it is not recommended as a crisis strategy for the decontamination of FFRs as it might be harmful to the wearer (CDC, 2020b). Further studies are needed to evaluate the antimicrobial efficacy of EO on the FFRs and the possibility of any ‘off-gassing’ from FFRs. Ultraviolet germicidal irradiation Ultraviolet (UV) irradiation is an electromagnetic irradiation having wavelength range between 100 and 400 nm. The wavelength 200–280 nm is called UV-C and commonly used for germicidal activities (Vazqez and Hanslmeier, 2006). The UV-C in the range of 250–270 nm is highly absorbed by the DNA and RNA of microorganisms, causing damage by dimerization of pyrimidine molecules, particularly the thymine molecule, and preventing multiplication (Gurzadyan et al., 1995). However, double-stranded DNA and RNA viruses need two times the UV irradiation dose compared with single-stranded DNA and RNA virus in order to achieve 90% inactivation (Tseng and Li, 2007). Ultraviolet germicidal irradiation (UVGI) has been widely used for the decontamination of FFRs during the COVID-19 pandemic (3M Company, 2020; Lowe, 2020; Mackenzie, 2020). There is no effect of UVGI on the filtration performance (Viscusi et al., 2007, 2009, 2011; Bergman et al., 2010; Fisher and Shaffer, 2011; Lore et al., 2012; Lin et al., 2018), fit (Viscusi et al., 2007, 2009, 2011; Bergman et al., 2010, 2011; Lindsley et al., 2015) and physical appearance (Viscusi et al., 2009; Bergman et al., 2010; Salter et al., 2010; Heimbuch et al., 2011) of FFRs. The antimicrobial efficacy of UVGI is promising against H1N1 virus (>99.99%, Heimbuch et al., 2011; ≥99.9%, Mills et al., 2018), H5N1 virus (>99.99%, Lore et al., 2012), and many other viruses (99.9%, Heimbuch and Harnish, 2020). However, a specific dose protocol and full surface area illumination are required for proper inactivation of the –microbes with minimal alteration of FFR functions. Also, the curved surfaces and ridge areas of a FFR may not receive the optimal dose of UV-C. Not all UV lamps provide the same intensity of UV irradiation (CDC, 2020b). So it is crucial to decide the number of UVGI disinfection cycles needed for the decontamination of each FFR model (CDC, 2020b). The decontamination method can be validated by using a UV-C-specific sensor to verify that 1 J cm−2 UV-C dose is applied at the FFR surface. The problem of UVGI is reflection and absorption of the UV light by the FFR material i.e. thickness of the textile material, chemical composition of the fibers and other materials like dyes and delustrants (Lindsley et al., 2015). The attenuation of the UV light decreases the antimicrobial efficacy against pathogens trapped in the inner layers of the FFRs (Lindsley et al., 2015). Fisher and Shaffer (2011) reported that to expose the innermost part, the internal filtering medium (IFM) of a FFR; to a given dose of UVGI, the exterior dose needed to be from 3.2 to 400 times the required interior level, depending upon the FFR model. Fisher and Shaffer (2011) recommended that a minimum of 1000 J m−2 was required for a 3-log (99.9%) reduction of viable MS2 coliphage at IFM. The UV-C has more biocidal efficacy than UV-A (Heimbuch and Harnish, 2020). The treatment time for each UV lamp has to be adjusted. Few studies reported a reduction in the durability of the FFR material following UV irradiation (Fisher and Shaffer, 2011; Lindsley et al., 2015; Mills et al., 2018; Heimbuch and Harnish, 2020). Lindsley et al. (2015) observed degradation of FFR at high (≥120 J cm−2) UV-C doses. Of 13 layers, 2 layers lost significant strength at 120 J cm−2, and 10 layers lost their significant strength at 950 J cm−2 and the overall the strength of the FFR fell more than 90% (Lindsley et al., 2015). Thus, the number of UVGI cycles should depend on the resistance of a FFR to degradation and the dose of UVGI used in the decontamination cycle. In turn, the dose of UVGI should be controlled by the amount of UVGI needed to inactivate any pathogen on the FFRs (Lindsley et al., 2015). UVGI can be harmful to humans and proper precautions are required to avoid skin and eye exposure (CDC, 2020b). Overall the UVGI does not involve hazardous chemicals and the system is compact and inexpensive. It can be deployed anywhere within a healthcare facility for quick and easy disinfection of FFRs. But UVGI is primarily a method for surface decontamination, the possible deep contamination in the FFRs remains a major concern, and to date, the FDA has not approved this method for FFR decontamination (FDA, 2020b). Autoclave Moist heat in the form of saturated steam under pressure is the most widely used decontamination process in healthcare organizations (Grinshpun et al., 2020). Moist heat kills microorganisms by irreversible coagulation and denaturation of enzymes and structural proteins (CDC, 2008b). The presence of moisture and temperature is crucial for the optimum decontamination of various items (CDC, 2008b). The effect of autoclaving on the filtration performance of FFRs is a major concern, as it adversely impacts fit (Viscusi et al., 2007; Grinshpun et al., 2020). The filtration efficiency of the FFRs decreases significantly following decontamination by autoclave (Viscusi et al., 2007; Grinshpun et al., 2020). The autoclave decontamination process leads to deformation, shrinking, mottling, and softening of FFRs (Viscusi et al., 2007). Temperatures above 80°C are likely to adversely affect the filter performance (Viscusi et al., 2007). Hutten (2007) recommends that the maximum filter operating temperature for nonwoven polypropylene is 90–100°C. The actual melting temperature of polypropylene is 165°C. But above the threshold temperature of 90–100°C, the FFR begins to soften and melt (Hutten, 2007). High temperature also affects the polymer properties (Fischbach et al., 2001). It is thus better that all decontamination processes for FFRs with polypropylene filters occur below the threshold temperature of 80°C, favoring low temperatures decontamination methods like VHP and UVGI. The biocidal efficacy of the autoclave process against Bacillus subtilis is 99–100% (Lin et al., 2018). There is no report mentioning the efficacy of autoclaving against any virus on the FFRs. The significant reduction in the filtration efficiency and deformation, stiffening and mottling of FFRs following autoclaving are the major limitation. As the particle penetration level following autoclaving remains above the NIOSH requirement, it is not recommended as a suitable method for the decontamination of FFRs (Viscusi et al., 2007, 2009). Microwave generated steam Microwave steam bags work at atmospheric pressure and thus are less destructive to FFRs (Bergman et al., 2011). The presence of moisture is a key factor for the biocidal effect (Jeng et al., 1987), thus in microwave generated steam (MGS), steam generated from the water passes through the FFRs enhancing the biocidal effect of the microwave irradiation treatment. The surface area of water reservoir, water volume, and microwave power level are crucial in relation to the exposure time (Lore et al., 2012). Smaller water surface area, large water volume, or microwave unit delivering <1250 W will require large exposure times to generate sufficient amount of steam (Lore et al., 2012). The MGS has no harmful effect on the filtration performance (Bergman et al., 2010; Fisher et al., 2011; Viscusi et al., 2011; Pascoe et al., 2020; Zulauf et al., 2020) and fit (Bergman et al., 2010; Heimbuch et al., 2011; Viscusi et al., 2011; Zulauf et al., 2020) of FFRs. In MGS, much of the microwave energy is absorbed by water and thus reducing the potential for damage to the filtration medium (Lore et al., 2012). MGS has little or no impact on functional integrity up to three decontamination cycles, but there may be FFR damage on the inner foam nose cushion and head straps (Bergman et al., 2010). This method demonstrates adequate antimicrobial efficacy against MS2 bacteriophage (99.99%, Fisher et al., 2011, >99.999%, Zulauf et al., 2020), H1N1 influenza viruses (>99.99%, Heimbuch et al., 2011), and S. aureus (>99.9999%, Pascoe et al., 2020). The FFRs made from hydrophilic materials may absorb water during the decontamination process (Fisher et al., 2011). Metal nosebands of FFRs may cause arcing and spark inside the microwave oven during the exposure to microwave (Viscusi et al., 2007; Lore et al., 2012). Although MGS has adequate antimicrobial activity and no negative effect on the filtration efficiency and fit factors of a FFR, but chances of arcing and spark inside the oven are major disadvantages of this method. Not all microwaves are with same power, few are more powerful than others. Further, the effect of higher power microwaves on FFRs is not known. Because small dimension microwave ovens do not allow a large number of FFRs to be decontaminated at a time, this method is not feasible in healthcare settings where rapid turnover of FFRs is required. Moist heat incubation Moist heat incubation (MHI) at 60–65°C under 80% relative humidity for 15–30 min has no effect on filter performance (Bergman et al., 2010; Viscusi et al., 2011; Lore et al., 2012) and fit (Bergman et al., 2010, 2011; Viscusi et al., 2011) of FFRs. The moist heat is more effective than dry heat for killing microorganisms and lower heat input is less likely to have deleterious results on filter performance (Hutten, 2007; Viscusi et al., 2007, 2009). A slight separation of the inner foam nose cushion (Bergman et al., 2010; Viscusi et al., 2011) and melting of head straps (Bergman et al., 2010) were observed in few FFRs. However, it had no effect on the physical deformation of the FFRs (Heimbuch et al., 2011). It is also highly effective against H1N1 (>99.99%, Heimbuch et al., 2011) and H5N1 (>99.99%, Lore et al., 2012) viruses. However, the CDC (2020b) has concluded that MHI does not have an adequate antimicrobial efficacy for various pathogens (CDC, 2020b). Although the MHI has no significant effects on the filtration and fit of FFRs, but it is a time-intensive method and may be useful for the decontamination of FFRs in very small organizations. Dry heat The dry heat decontamination process is accomplished by heat conduction. In this method, heat is absorbed by the outer surface of an item and then passed into the inner layer. Thus, the item must be dry before undergoing the dry heat decontamination process. Dry heat kills microorganisms by inducing the coagulation of proteins. Dry heat at 70°C for 30 min has been suggested as an effective decontamination method for FFRs (Yim et al., 2020). The National Institutes of Health (NIH) has also been validated dry heat at 70°C to inactivate SARS-CoV-2 viruses (Fischer et al., 2020). It maintains the integrity of the filters for re-use (Viscusi et al., 2007, 2009; Lin et al., 2018; Pascoe et al., 2020; Yim et al., 2020). Several reports suggest that two cycles of dry heat at 70°C for 30 min can kill viruses without altering respirator fit (Gurzadyan et al., 1995; Vazqez and Hanslmeier, 2006). Dry heat has adequate biocidal efficacy against B. subtilis (99–100%, Lin et al., 2018), S. aureus (99.99%, Pascoe et al., 2020), and SARS-CoV-2 viruses (<99.9%, Fischer et al., 2020). A chance of melting of the filter media at the ends of metal nosebands of FFRs is very high with a dry heat process (Viscusi et al., 2007, 2009). An increase in dry heat temperature above the maximum operating temperature of 90–100°C leads to the softening and melting of FFRs (Hutten, 2007). Viscusi et al. (2007) reported decreased filtration performance and melting of FFRs at 160°C, but dry heat at 80°C reduced these effects significantly. Recently Yim et al. (2020) also observed fracture and fiber expansion of FFRs when heated at 150°C, but the filtration efficiency, fit factor, and dipole charge density remained within the normal range when heated at 70°C for 30 min (Yim et al., 2020). Dry heat is an effective decontamination method having no known health hazards to the users (Viscusi et al., 2009). Lin et al. (2018) have suggested that a traditional electric rice cooker without water can also be used. However, the process is very slow and needs a prolonged time for the deactivation of viruses and other microbes. The chance of melting of a FFR is very high. The CDC has actively recommended against using dry heat for the decontamination of FFRs (CDC, 2020a). Bleach Chlorine bleach is a common household decontaminant. The hypochlorous acid of bleach causes microorganism proteins to clump together, which prevents growth. Three studies reported that treatment with 0.6% bleach for 30 min had no effect on FFRs filtration performance (Viscusi et al., 2009; Bergman et al., 2010; Lin et al., 2018). However, one study used 0.5% bleach for 10–30 min and found a moderate negative effect on the filtration performance of FFRs (Viscusi et al., 2007). Treatment of FFRs with 5.25% bleach for 30 min resulted in the stiffening of filter media and elastic straps of FFRs (Viscusi et al., 2007). Bleach has 99–100% biocidal efficacy against the B. subtilis (Lin et al., 2018). The presence of chlorine residue on the respirator, tarnishing of metal nosebands, irritation to eyes, skin, and respiratory tract, and chlorine odor are a major concern of bleaching (Viscusi et al., 2007, 2009; Salter et al., 2010). Viscusi et al. (2009) recommended decontamination of FFRs by bleach should be further evaluated. Due to lack of availability of the antimicrobial efficiency of bleach against viruses and spores on the FFRs, bleach is not a recommended method for FFR decontamination. Liquid hydrogen peroxide Immersion of FFRs in 3–6% hydrogen peroxide liquid for 30 min has no effect on their filtration performance (Viscusi et al., 2007; Bergman et al., 2010). There is no report related to the fit of FFRs and biocidal efficacy. The risk of bubble formation during the FFR submersion may decrease its biocidal efficacy. However, fading of label ink on the fabric, oxidation of staples, and presence of oxidant residues on the FFRs are major concerns (Viscusi et al., 2007, 2009; Bergman et al., 2010; Salter et al., 2010). Due to lack of evidence on antimicrobial efficacy of liquid hydrogen peroxide on the FFRs, we recommend not to use it for the decontamination of FFRs. Alcohol Not all types of alcohol are equally effective against all microorganisms. Alcohol kills microorganisms by breaking down their cell walls. The drawback of electrets filter media is that when exposed to certain chemicals, it loses its electrostatic charge leading to decreased filtration performance and increased filter penetration (Viscusi et al., 2007). Organic chemicals such as ethanol and isopropyl alcohol cause significant deterioration of filtration performance of respirators containing electret filters (Martin and Moyer, 2000; Janssen et al., 2003; Jasper et al., 2006). Viscusi et al. (2007) observed a marked increase of average filter penetration following 1 s and 1 min submersion of N95 FFRs in isopropyl alcohol. Isopropyl alcohol causes severe degradation of electret filters after exposure (Martin and Moyer, 2000; Janssen et al., 2003). It has also been observed that isopropyl alcohol alters the density and/or spatial distribution of the electret charges on the surface of polymer fibers, thus leading to increase filter penetration (Jasper et al., 2005). Recently Grinshpun et al. (2020) observed a decrease filtration efficiency following the decontamination of FFRs with 70% ethanol. However, one study reported that the filter quality was maintained following the decontamination of N95 FFRs by 70% ethanol (Lin et al., 2018). The fit of FFRs following alcohol decontamination is not known. The biocidal efficacy of alcohol is very poor, i.e. 73 ± 5% to 22 ± 8% survival decay of B. subtilis in 24 h (Lin et al., 2018). As the filtration performance of a FFR is badly affected by the 70% isopropyl alcohol, it is not recommended for the decontamination of FFRs (Viscusi et al., 2007, 2009). Disinfection wipes Hypochlorite and benzalkonium chloride solution wipes have been tried for the decontamination of FFRs and had no effect on the filtration performance (Heimbuch et al., 2014). The antimicrobial efficacy against S. aureus was found as 99.9–99.999% (Heimbuch et al., 2014). There is no study evaluating their effectiveness against viruses on the FFRs. Thus, disinfection wipes are not recommended for the decontamination of FFRs for SARS-CoV-2 viruses Dimethyldioxirane The dimethyldioxirane (DMDO) is a liquid decontaminant consisting of 10% Oxone, 10% acetone, and 5% sodium bicarbonate (Salter et al., 2010). There are no data mentioning its antimicrobial efficacy, effect on filtration performance and fit of FFRs. Only one study observed accumulation of visible white residues of DMDO on FFR surfaces following their submersion for 30 min and then 18 h off-gassing (Salter et al., 2010). Due to lack of literature, DMDO should not be tried for the decontamination of FFRs during ongoing COVID-19 pandemic. Soap and water Water has no effect on filter performance, but soap can have a negative impact, because it is thought to degrade the electret fiber charge, similar to the effect observed with isopropyl alcohol (Viscusi et al., 2007). Bierman et al. (1982) noticed that the addition of surfactant to an ionic water solution resulted in a dramatic decrease in filter efficiency for permanently charged electret filters. There is no study evaluating the effect of soap and water on filter performance and fit of FFRs. Further, there is no study evaluating the antimicrobial efficacy of soap and water. Due to lack of important data on FFR performance and microbial contamination following application of soap and water, this method is not recommended for FFR decontamination. Discussion Decontamination and re-use of FFRs are not recommended routinely as it is inconsistent with the established NIOSH regulations. Also NIOSH respirator certification regulations do not include FFR decontamination provisions (CFR, 1995). The FDA 510(k) clearance also designates that all FDA-approved N95 FFRs are labeled as ‘single use’, disposable devices (Bergman et al., 2011). However, limited re-use of disposable FFRs has been suggested only as a crisis capacity strategy to conserve the available supplies for healthcare organizations during a pandemic. Currently, CDC has also adopted ‘extended use and limited re-use’ strategy for FFRs (CDC, 2020a). Literature supports that SARS-CoV-2 viruses survive up to 72 h on plastic, stainless steel, and cardboard surfaces (van Doremalen et al., 2020). One option to prevent the transfer of pathogens from FFRs to wearer during re-use is to issue five FFRs to each healthcare worker, who will were one FFR on each day and re-use the same after 5 days (CDC, 2020b). However, if the supplies are even more limited then decontamination of FFRs is necessary (CDC, 2020b). As per the Institute of Medicine (IOM), the FFR decontamination method should remove any biological contamination which can affect the health of the user, and without compromising their filtration performance and fit (IOM, 2006). Although we have described a wide range of methods for the decontamination of FFRs, many of these have significant shortcomings or are lacking in important information about the impact on respirator performance. No decontamination method was found best for all types of FFRs. Before selecting a particular method, the manufacturer should be consulted for a better understanding in the impact of a decontamination method on the FFR filtration and fit. Also if any information from a third party is available showing that FFRs can be successfully decontaminated without affecting their filtration and fit performances, then FFRs can be decontaminated in accordance with those recommendations (CDC, 2020b). However, in the absence of any available guidelines or when information is available that a FFR cannot be decontaminated without negatively impacting their filtration and fit; then also FFRs can be decontaminated, but these FFRs should not be worn by a healthcare provider while performing an aerosol-generating procedure (CDC, 2020b). The FDA has issued guidelines on FFR decontamination defining specific log reductions of specific microorganisms during the ongoing COVID-19 public health emergency (FDA, 2020c). The guideline suggests that the decontamination method should demonstrate >6-log i.e. 99.9999% sporicidal or mycobactericidal efficacy for single or multiple uses. Most of the decontamination methods discussed in this review failed to demonstrate this level of efficacy, with the exception of the SteraMist Binary Ionization Technology (BIT) which used ionized H2O2 (iHP) and demonstrated at least 9-log (>99.9999999%) reduction of G. stearothermophilus spores in FFRs following their decontamination. Another study also reported no detection of SARS-CoV-2 virus following decontamination of FFRs in VHP plasma sterilization (Ibáñez-Cervantes et al., 2020. However, further studies are needed to support these claims. We reviewed 13 different FFR decontamination methods. Considering various aspects like antimicrobial efficacy, effect on filtration performance and fit factor, safety to the users, and cost of a decontamination cycle, we found that VHP is the most suitable method. Jatta et al. (2020) observed no change in the filtration performance and fit of FFRs up to five cycles of H2O2 decontamination. The Battelle report showed that FFRs can be decontaminated up to 50 times without altering their filtration performance (Battelle report, 2016). However, from the safety point of view, CDC has recommended five times of decontamination (CDC, 2020a). High cost and unavailability of a FDA-approved VHP machine in majority of healthcare organization are the major challenge to this decontamination method. The UVGI could be the next suitable method for the decontamination of FFRs. An appropriate dose, selection of a suitable FFR model and exposure of full surface area are key issues for successful decontamination by UVGI. The third most suitable method would be the dry heat decontamination at 70°C for 30 min. Although the chances of FFR melting and sparking are there, but this method can be used for three times decontamination of FFRs (Pascoe et al., 2020; Yim et al., 2020). Although few evidences are there in the literature favoring MGS and MHI methods, but we feel those are inadequate to recommend them to use in healthcare organizations. The risk–benefit ratios for other methods like EO, autoclave, bleach, liquid hydrogen peroxide, disinfection wipes, alcohol, DMDO, and soap and water are very high and should not be used for the decontamination of FFRs. Conflict of interest None declared. References 3M Company . ( 2020 ) Decontamination methods for 3M N95 respirators. 2020. Revision 4 . Available at https://multimedia.3m.com/mws/media/1824869O/decontamination-methods-for-3m-filtering-facepiece-respirators-technical-bulletin.pdf. Accessed 22 April 2020 . Battelle . ( 2016 ) Final report for the Bioquell Hydrogen Peroxide Vapor (HPV) decontamination for re-use of N95 respirators . 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Published by Oxford University Press on behalf of the British Occupational Hygiene Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Decontamination Strategies for Filtering Facepiece Respirators (FFRs) in Healthcare Organizations: A Comprehensive Review
JF - Annals of Work Exposures and Health (formerly Annals Of Occupational Hygiene)
DO - 10.1093/annweh/wxaa090
DA - 2021-01-14
UR - https://www.deepdyve.com/lp/oxford-university-press/decontamination-strategies-for-filtering-facepiece-respirators-ffrs-in-MKPSQag8x0
SP - 26
EP - 52
VL - 65
IS - 1
DP - DeepDyve
ER -