key: cord-0925196-e8wfmsxx authors: Paul, D.; Gupta, A.; Maurya, A. K. title: Exploring options for reprocessing of N95 Filtering Facepiece Respirators (N95-FFRs) amidst COVID-19 pandemic: a systematic review date: 2020-09-03 journal: nan DOI: 10.1101/2020.09.01.20179879 sha: 785ee4262d9bc2536a67be7938de75185b77bf7a doc_id: 925196 cord_uid: e8wfmsxx Background: There is global shortage of Personal Protective Equipment due to COVID-19 pandemic. N95 Filtering Facepiece Respirators (N95-FFRs) provide respiratory protection against respiratory pathogens including SARS-COV-2. There is scant literature on reprocessing methods which can enable reuse of N95-FFRs. Aim: We conducted this study to evaluate research done, prior to COVID-19 pandemic, on various decontamination methods for reprocessing of N95-FFRs. Methods: We searched 5 electronic databases (Pubmed, Google Scholar, Crossref, Ovid, ScienceDirect) and 1 Grey literature database (OpenGrey). We included original studies, published prior to year 2020, which had evaluated any decontamination method on FFRs. Studies had evaluated a reprocessing method against parameters namely physical changes, user acceptability, respirator fit, filter efficiency, microbicidal efficacy and presence of chemical residues post-reprocessing. Findings and Conclusions: Overall, we found 7887 records amongst which 17 original research articles were finally included for qualitative analysis. Overall, 21 different types of decontamination or reprocessing methods for N95-FFRs were evaluated. Most commonly evaluated method for reprocessing of FFRs was Ultraviolet (Type-C) irradiation (UVGI) which was evaluated in 13/17 (76%) studies. We found published literature is scant on this topic despite warning signs of pandemic of a respiratory illness over the years. Promising technologies requiring expeditious evaluation are UVGI, Microwave generated steam (MGS) and Hydrogen peroxide vapor (HPV). Global presence of technologies, which have been given Emergency use authorisation for N95-FFR reprocessing, is extremely limited. Reprocessing of N95-FFRs by MGS should be considered for emergency implementation in resource limited settings to tackle shortage of N95-FFRs. Shortage of FFRs is not new, pangs of which were first felt during 2003 SARS outbreak [9] . It has been predicted for an impending influenza pandemic consequent to which U.S. Strategic National Stockpile had plans for providing 100 million N95-FFRs nationally, but it was deemed insufficient in event of a longer pandemic [9] [10] [11] . Hence, in 2006, Institute of Medicine (IOM) constituted a committee to address reusability of facemasks. Reuse of an FFR was defined as repeatedly donning and doffing of respirator by the same wearer, with or without undergoing reprocessing in between, till it is discarded. The committee recommended reuse of respirators in the event of acute shortage provided they are not obviously damaged or soiled [11] . However, committee specified that no method exists currently for reprocessing of N95-FFRs and identified it as a research priority [11] . Consequently, various research groups began their quest to search a reprocessing method which is efficacious against respiratory pathogens, is safe for human use and maintains the integrity of various components of the respirator. Even after a decade of research, prior to COVID-19 pandemic, no method has been recommended for reprocessing of N95-FFRs. Hence, we conducted this systematic review to determine the status of research done, prior to COVID-19 pandemic, to identify technologies which can be utilized for reprocessing of N95-FFRs in present situation and can be explored in near future to tackle the global crisis of respirator shortage. We report this systematic review (PROSPERO ID: CRD42020189684) in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [12] and checklist is provided in S1 Table. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint independently by all three reviewers. Extracted data was checked and analysed by one reviewer (AG) and disagreements were resolved prior to final analysis. To assess methodological quality and risk bias of studies, a self-developed tool was designed on the basis of STROBE statement [13] due to unavailability of a validated quality assessment tool for such studies. Two authors (AKM and DP) independently assessed the methodological quality and risk bias as per tool. The scheme of scoring and grading of studies is given in S3 Table along with the final quality assessment results. Inter-author concordance on grading of studies was evaluated by third author (AG). Final quality assessment results for included studies, as shown in S3 Table, were prepared by resolving inter-author disagreements by discussion and building consensus. Our search strategy identified 7887 records of which 17 original research articles fit inclusion criteria for qualitative analysis, methodology of the same has been described in Fig 1. No records were found in OpenGrey database using search strategy. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint Of 17 studies, 14 were graded as high quality and 3 as moderate quality (S3 Table) . Inter-author agreement in grading of studies was 88% (15/17). Overall agreement in quality assessment scores was 64% (11/17). Amongst 17 included studies, 15 were conducted in U.S. University [28, 29] . First study evaluating reprocessing methods for FFRs was published in 2007 [22] and last study in 2018 [29] . Overall, 21 different types of decontamination or reprocessing methods for N95-FFRs were evaluated in included studies against various parameters namely physical changes, user acceptability, respirator fit, filter efficiency, microbicidal efficacy and presence of chemical residues post-reprocessing. Number of studies conducted for each reprocessing method, on these parameters are given in Fig 2. Overall, these studies evaluated 9 Physical (Energetic) reprocessing methods namely Ultraviolet (UV-C) Irradiation (UVGI) [8, [14] [15] [16] 19, 20, [23] [24] [25] 27, 29] , UV-A [29] , UV-B [27] , Moist heat delivered using Microwave generated Steam (MGS) [14, 15, 20, 22, 23, 26] , Lab Incubator (MHI) [14, 15, 20, 22, 23] and Autoclave All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint (MHA) [22, 28, 29] , Dry heat delivered by Microwave (MGI) [16, 22] , Hot Air Oven (DHO) [22] and Traditional Electric Rice Cooker (TERC) [28, 29] 25, 27] , intact respirators were exposed to the decontamination method whereas in 5, cut pieces of facepiece portion were exposed[8, 24, 26, 28, 29] . Furthermore, in one study, 8 pieces of straps were also exposed separately to UVGI. In 4 studies, FFRs underwent multiple cycles (3 in all studies) of decontamination for reprocessing [14, 17, 18, 23] . (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. In 10 of 17 studies, the identities of N95-FFR models used was disclosed [8, 15, 17, 19, 21, [23] [24] [25] 28, 29] , details of which against the reprocessing method and parameters evaluated are given in S4 (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint respirator, was exposed to 7 different reprocessing methods. Furthermore, in 2 studies, P100 respirators were also evaluated but in both identities were not disclosed [16, 22] . Thirteen studies [8, [14] [15] [16] [19] [20] [21] [22] [23] [24] [25] 27, 29 ] evaluated exposure to UV-C (254 nm) as a reprocessing method for FFRs, as shown in Fig 2. All 22 known models of N95-FFRs were reprocessed using UV-C in at least one study (S4 Table) . Furthermore, one study each also examined the microbiological efficacy of UV-A [29] and presence of chemical residues after using UV-B [27] . Exposure variables of UVGI on N95-FFRs and summary of results are provided in Table 1 . Different parameters evaluated against UVGI are detailed in Fig 2. Since, UV-C has been the most commonly evaluated method for reprocessing of N95-FFRs, it will be discussed in detail. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . Table 4 . All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. while tackling pathogens against whom their use is mandatory such as Mycobacterium tuberculosis, as they are not available due to cost [39, 40] . Finding a reprocessing method for FFRs will led to provision of adequate respiratory protection for HCWs in such resource limited settings. A typical N95-FFR consists of facepiece covering mouth and nose, outer margin of which is lined to provide a face seal to the wearer. Two straps are attached to facepiece for fitting All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint snugly at the back of head, a pliable metallic nose piece to facilitate bending at the nasal bridge and a foam cushion beneath it for the comfort of the wearer [41] . The function of an N95-FFR is to provide wearer an air supply free of particulates, including bioaerosols. This is facilitated by the main filtering layer of the respirator, also termed as Electret media, which is made up of non-woven, electrostatically charged polypropylene fibers which can capture the particulates in the incoming air [14] . However, the wearer must ensure that inhaled air should reach him through the facepiece and not through sides of the respirator. To ensure this, a wearer should undergo fit testing annually to determine the best respirator design and size for their facial features. Additionally, at the time of donning, wearer must ensure a user face-seal check to determine any air leak from the sides of respirator [41] . N95-FFRs are difficult to decontaminate owing to the porous nature of the main body and electrostatically charged nature of electret media. Any reprocessing or decontamination method, despite being microbiologically efficacious, shall be able to preserve the functioning of electret media, not physically affect various structural components compromising respirator fit and face-seal. Furthermore, due to proximity of N95-FFR to face, it should be devoid of harmful chemical residues, as they can be inhaled. Additional considerations for selecting a reprocessing method for reusing N95-FFRs for a healthcare facility are existing infrastructure, cost, turnaround time and throughput of the method [41] . Till date, whatever meagre research has been done, it has failed to find a reprocessing method which ticks all the boxes. Physical (Energetic) methods such as application of moist heat, dry heat and irradiation have traditionally been the most commonly used methods for reprocessing healthcare items. Amongst them, Irradiation by UV-C (254 nm) rays (UVGI) has been the most frequently All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint evaluated reprocessing methods for N95-FFRs, as shown in Fig 2 and Table 3 . In all these studies, UVGI has shown to cause no damage to the physical appearance of FFRs, acceptable to users in terms of odor, donning ease and wear comfort, maintain respirator fit, preserve filter efficiency even after undergoing multiple cycles of decontamination and devoid of any toxic residues post-exposure. Dose of irradiation is the most important variable for determining microbicidal efficacy of UVGI, which, in turn, is determined by irradiance at the surface of FFR and duration of exposure [19] . Total doses around 1-2 J/cm 2 have shown to provide ≥4 log 10 reduction of viruses inoculated on FFRs and around 5-6 J/cm 2 against bacterial spores. Overall, UVGI has shown to be a suitable choice for reprocessing of FFRs, however, it is limited by varying exposure variables of UV dose used in multiple studies, as shown in Table 1 . Furthermore, a study Fisher et al [24] concluded that the UV-C dose required for microbicidal efficacy is a function of the dose available to the electret medium, which in turn, is dependent on the penetrance (transmittance) of the layer above it. Hence, effective doses of UV-C for microbicidal efficacy will be model specific and needs to be established accordingly. We conclude that UVGI has great potential to be utilized as an effective decontamination method for N95-FFRs during this time of crisis however, more studies are needed to validate the various variables associated with the delivery of the UVGI method and respirator model specific doses will need to be established before it can be recommended. Moist heat has been delivered in the form of steam generated in a microwave (MGS), benchtop lab incubator (MHI) at 60-70°C and in traditional Autoclave (MHA). Of them, MHA has shown to physically destroy FFRs and is deemed unsuitable for the purpose [22] . In MHI, exposure time has varied from 15-30 min and in MGS N95-FFRs are exposed for 90-All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint 120s. Multiple studies evaluating physical changes by both methods noticed partial separation of inner foam nose cushion. However, this was noticed for a particular FFR model (3M1870), where model identity was disclosed, but effect was not pronounced after undergoing multiple cycles of decontamination [14, 23] . Both methods are shown to have no significant effect on user acceptability, respirator fit and filter efficiency till 3 cycles of decontamination [14, 15, 21, 23] . More than 4 log 10 reduction of enveloped viruses was demonstrated on N95-FFRs undergoing decontamination by MGS and MHI methods [15, 17, 20, 26] . We are of opinion that these methods are low cost, easily doable in any setting, but require more validation in terms of other respirator models and cycles of decontamination, in future studies. MGS method is particularly suitable for implementation by individuals at home and smaller healthcare settings. Sparking due to placing metallic components in microwave has been a concern but it has not been noticed in MGS method [14] . Dry heat has been evaluated as a reprocessing method for FFRs in 4 studies[16, 22, 28, 29] In two studies using DHO, FFRs were able to physically withstand temperatures till 80°C without affecting durability and filter efficiency [16, 22] Electric rice cooker delivering temperature of 149-164°C has been used in studies from Taiwan[28,29] and one study from there found that exposure of an FFR model for 3 minutes was able to provide 99-100% biocidal efficacy against Bacillus subtilis spores [29] . In a study where microwave oven was used to deliver dry heat for 2 min, 2 of 9 respirator models were destroyed but in 7 models which withstood the treatment, filter efficiency was unchanged [16] . We opine that the literature is insufficient to either recommend or refute dry heat as a method of reprocessing for FFRs. All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint Exposure to Ethylene oxide (EO) and Hydrogen peroxide (H 2 O 2 ) have been evaluated as a decontamination method for N95-FFRs simultaneously in 4 studies [14, 16, 22, 27] . They are ideally suited for temperature sensitive articles hence, their use for reprocessing N95-FFRs is particularly promising. In these studies, FFRs have been exposed to EO and H 2 O 2 (HPGP) in their respective sterilizers for standard cycling conditions. In addition, a study by Viscusi et al [22] , vaporized H 2 O 2 (HPV) generated in a commercial, automated vapor generator (BIOQUELL) was used for reprocessing of FFRs. Detailed cycling conditions of individual studies are given in Table 3 . FFR models were not disclosed in any of the studies. After EO FFRs which had undergone EO sterilization [27] . No study yet has evaluated microbicidal efficacy of EO sterilization on FFRs though it is expected that this method will achieve adequate microbicidal efficacy. Overall, we opine that though EO has performed suitably in maintaining the physical architecture and filtration efficiency, increasing its safety profile by increasing aeration duration should be the topic of further research studies. Hence, it cannot be recommended at this point of time for reprocessing of N95-FFRs due to safety concerns. Hydrogen peroxide provides microbicidal activity by way of generating free radicals and its degradation products are safe. In 3 studies, where HPGP was evaluated, no significant physical changes on the FFRs were noted [14, 16, 22] . Filter efficiency of 25% (9/36) respirators was noted to be degraded in one [14] of three [14, 16, 22] studies which evaluated. However, this effect was not noted when FFRs were treated with vaporized form [22, 42] . In a commercial evaluation done for FDA by Batelle Institute on Clarus C HPV generator in All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint 2016, no filter degradation was noted on 3M1870 even after undergoing 50 cycles of decontamination [42] . This system has been granted emergency use authorization (EUA) by FDA, after COVID-19 pandemic, for reprocessing N95-FFRs [43] . Concerns have been raised regarding throughput of HPGP as in a study authors noticed cycles were aborted in STERRAD® Sterilizer whenever >6 FFRs were placed [27] . This could be due to presence of cellulose in the straps of the respirators leading to absorption of H 2 O 2 [27] . assessed for presence of toxic residues post-exposure [27] . Overall results were LHP oxidized staples of FFRs at 6% but not at 3% strength, filter efficiency of FFRs was maintained at both concentrations and they were devoid of toxic chemical residues after processing. Microbiological efficacy has not been studied yet in any study. Bleach has been most frequently evaluated liquid disinfectant for reprocessing of FFRs. Overall bleach has been evaluated in 9 studies of which 1 used disinfectant wipes [18] . All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint Exposure to bleach caused physical changes in the FFRs in terms of being stiff, mottled and tarnishing of metallic nosepieces [14, 16, 18, 22] . Offensive odor from FFRs was noticed in most studies [14, 16, 27] . Furthermore, chlorine release has been noted when respirators were exposed to moisture, raising concerns regarding the safety of this method if a person breathes through it [16, 27] . Though it has been found to have no significant degradation in the filter quality of the FFRs [14, 16, 18, 22] and have excellent microbicidal efficacy [18, 25, 26, 29] , bleach is not safe to decontaminate FFRs. Alcohols (Ethanol and Isopropyl alcohol) have also been evaluated in 3 studies, but they are known to significantly degrade the filter efficiency due to removal of electrostatic charges from the electret media [22, 28, 29] . Hence, they don't hold further merit in this discussion. Similar findings have been noted in one study which used soap & water for decontamination of FFRs [22] . 23] and chemical safety in 1 study [27] . Hence, changes in these parameters which are not studied much, nevertheless are important, should be the focus of future studies. Furthermore, we didn't do a meta-analysis as the studies were heterogeneous in terms of exposure variables and the number of studies conducted were less for a particular All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint reprocessing method: parameter combination. As we write this review, a large body of literature on reprocessing of N95-FFRs has been already published till 30 th June 2020 [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] . but when we did literature search, only few studies were published [44, 45, 49, 58] To summarize, reusing N95-FFRs is need of the hour due to COVID-19 pandemic. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. Evaluation of multiple (3-cycle) decontamination processing for filtering facepiece All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. Impact of three biological decontamination methods on filtering facepiece respirator All rights reserved. No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint WHO. 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(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: Effects of five decontamination methods Relative survival of Bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods A cluster randomised trial of cloth masks compared with medical masks in healthcare workers Estimating Reusability of Organic Air-Purifying Respirator Cartridges Effectiveness of common healthcare disinfectants against H1N1 influenza virus on reusable elastomeric respirators Assessment of half-mask elastomeric respirator and powered air-purifying respirator reprocessing for an influenza pandemic Maintenance status of N95 respirator masks after use in a health care setting No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted Reaerosolization of MS2 bacteriophage from an N95 filtering facepiece respirator by simulated coughing The effect on fit of multiple consecutive donning and doffing of N95 filtering facepiece respirators Stability of SARS-CoV-2 in different environmental conditions Tuberculosis infection control practices in a high-burden metro in South Africa: A perpetual bane for efficient primary health care service delivery Barriers and motivators affecting tuberculosis infection control practices of Russian health care workers Considerations for recommending extended use and limited reuse of filtering facepiece respirators in health care settings No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted doi: medRxiv preprint Battelle. Final Report for the Bioquell Hydrogen Peroxide Vapor (HPV) decontamination for reuse of N95 respirators Battelle CCDS Critical Care Decontamination System TM being deployed to meet urgent need for personal protective equipment for Nation's healthcare workforce critical-care-decontamination-system-being-deployed-to-meeturgent-need-for-personal-protective-equipment-for-nation-s-healthcare-workforce Steam treatment for rapid decontamination of N95 respirators and medical face masks Decontamination and reuse of N95 respirators with hydrogen peroxide vapor to address worldwide personal protective equipment shortages during the SARS-CoV-2 (COVID-19) pandemic Hydrogen peroxide vapor sterilization of N95 respirators for reuse N95 Mask Decontamination using standard hospital sterilization technologies No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted Microwave-Generated steam decontamination of N95 respirators utilizing universally accessible materials Effectiveness of Ultraviolet-C light and a high-level disinfection cabinet for decontamination of N95 respirators Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: Impact on their performance and integrity Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C Effectiveness of N95 respiratoR decontamination and reuse against SARS-CoV-2 N95 Reprocessing by low temperature sterilization with 59% vaporized hydrogen peroxide during the 2020 COVID-19 Pandemic It's not the Heat, it's the humidity: Effectiveness of a rice cooker-steamer for decontamination of cloth and surgical face masks and N95 Respirators No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted Development of a Highly effective low-cost vaporized hydrogen peroxide-based method for disinfection of personal protective equipment for their selective reuse during pandemics Aerosolized hydrogen peroxide decontamination of N95 respirators, with fit-testing and virologic confirmation of suitability for re-use during the COVID-19 pandemic Proposal for a EN 149 acceptable reprocessing method for FFP2 respirators in times of severe shortage Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports No reuse allowed without permission. (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted After Inter-Author Agreement) S4 Table: Summary of various reprocessing parameters evaluated for specific FFR models (where disclosed in included studies) by various reprocessing methods Abbreviations: P-Physical, O-Odour Potential Conflicts of Interest: All authors report no conflicts of interest relevant to this article. All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint All rights reserved. No reuse allowed without permission.(which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint this version posted September 3, 2020. . https://doi.org/10.1101/2020.09.01.20179879 doi: medRxiv preprint