Table 1.

Characteristics of the published studies included considering in vitro studies, letters and other studies designs.

Article	Objective	Decontamination regimens tested or discussed	Organisms tested or discussed	Organisms used as coronavirus organism	Method of evaluation	Main findings
IN VITRO STUDIES
Anderegg et al. 2020	This research studied the effect of five cycles of heating to 85 °C for 30 min with a relative humidity of 60−85%	Heat and humidity	–	–	–	Authors found that for all of the N95 models we investigated there was no significant difference in filtration efficacy between the test groups of masks and the untreated control masks.
Cadnum et al. 2020	The goal of the current study was to examine the effectiveness of UV-C light and a high-level disinfection cabinet for decontamination of N95 respirators.	Ultraviolet-C Light, Multi-purpose high-level disinfection cabinet that generates aerosolized peracetic acid and hydrogen peroxide and dry heat	Bacteriophages MS2, Bacteriophages Phi6, Bacteriophages Phi X174, Acinetobacter baumanii, Vancomycin-resistant, Enterococcus faecium, NDM1-producing Klebsiella pneumoniae, Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Candida auris, Candida albicans, Clostridioides difficile, Bacillus subtilis	Bacteriophage Phi6	methicillin-resistant Staphylococcus aureus MRSA test strain	The study found that UV-C reduced contamination of N95 respirators with Phi6 and MS2 bacteriophages and MRSA. However, efficacy varied with different respirator types and with different locations on the respirator. A high-level disinfection cabinet using submicron droplets of aerosolized peracetic acid and hydrogen peroxide was substantially more effective for decontamination of N95 respirators and with 3 consecutive cycles or a single extended cycle achieved >6-log10 reductions meeting criteria for disinfection.
Banerjee et al. 2020	Authors proposed to combine two systems such as Warm Moist Heat standalone and Ultraviolet Germicidal Irradiation standalone to harness the combined synergistic advantages into a hybrid model called Warm Ultra Violet Hybrid Model	UV irradiation and heat treatment	–	–	–	Application wise this hybrid model may be used for medical, industrial, domestic and personal sanitization purposes. Moreover, this model is not only restricted to SARS-CoV-2 but can be used to treat any type of virus/ bacteria.
Bopp et al. 2020.	To examine the efficacy of autoclave-based decontamination for the reuse of single-use surgical masks and N95 filtering facepiece respirators	Moist heat autoclave	–	–	–	The specific surgical masks and N95 FFR models can withstand autoclave decontamination for up to three cycles
Czubryt et al. 2020	Authors assessed potential re-use via autoclaving of N95 respirator masks worn daily in a major urban Canadian hospital	Sterilization by autoclaving	–	–	–	Reuse of N95 respirator masks is feasible in major hospitals and other healthcare facilities. Such reuse requires development of a comprehensive plan that includes communication across staffing levels, from front-line workers to hospital administration, to increase the collection, acceptance of and adherence to sterilization processes for N95 respirator masks recovery
Daeschler et al. 2020	Authors investigated whether thermal disinfection at 70 °C for 60 min inactivates pathogens, including SARS-CoV-2, while maintaining critical protective properties of N95 respirators for multiple cycles of disinfection and reuse in a real-world setting	Thermal disinfection in cycles of 60 min at 70 °C, at either 0% or 50% relative humidity	Escherichia coli	SARS-CoV-2	CFU	Thermal disinfection successfully decontaminated N95 respirators without impairing structural integrity or function.
Fischer et al. 2020	Not reported	UV light, heat treatment, 70 % ethanol, vaporized hidrogen peroxide	Not reported	HCoV-19 nCoV-WA1−2020	Cytopathogenic effect was scored and the TCID50 was calculated	NR
Grinshpun et al. 2020	Authors evaluated common surgical masks and N95 respirators with respect to the changes in their performance and integrity resulting from autoclave sterilization and a 70 % ethanol treatment	Sterilization in na autoclave under 250oF, 15 psi for 30 min, fast exhaust following by drying for 30 min, for 5 times; treatment of facepieces by soaking in 70 % ethanol for two hours	–	–	–	The initial collection efficiency and the filter breathability may be compromised by sterilization in an autoclave and ethanol treatment. The effect depends on a protective device, particle size, breathing flow rate, type of treatment and other factors. Additionally, physical damages were observed in N95 respirators after autoclaving.
Hankenson et al. 2020	Authors describes the intensive developmental process that was necessary to convert a multiroom animal housing facility into a regional vaporized hydrogen peroxide decontamination center in response to the impact of the coronavirus pandemic in the United States	Vaporized hydrogen peroxide	–	–	–	Authors did not have access to confirmed COVID-19 samples to test eradication of coronavirus by the hydrogen peroxide fogging system; however, the EPA data for this chemical confirm virucidal activity.
Ibáñez-Cervantes et al. 2020	Authors investigated the disinfection of N95 masks artificially contaminated with SARS-CoV-2 and ESKAPE bacteria by using hydrogen peroxide plasma	Hydrogen peroxide plasma	ESKAPE bacteria (Acinetobacter baumannii and Staphylococcus aureus)	SARS-CoV-2	Amplification of specific genes by RT-PCR and CFU	Disinfection of N95 masks by using the hydrogen peroxide plasma technology can be an alternative for their reuse in a shortage situation.
Jatta et al. 2020	Authors aimed to use a readily available local resource to prolong our institutional supply of N95 respirators during a crisis capacity while maintaining the safety of frontline providers	59 % vaporized hydrogen peroxide	–	–	–	Authors have successfully demonstrated that N95 respirator decontamination with vaporized hydrogen peroxide at 59 % hydrogen peroxide can be safely utilized to decontaminate single-use N95 respirators without significant effects on filtration efficiency or quantitative fit testing. (deixei isso p discutir caso precise): Authors believe it is important to note that decontamination methodologies should only be used as crisis capacity as these respirators were designed for single-use. Without appropriate expertise and logistics, the authors would not recommend respirator decontamination and would recommend only extended use of respirators per Centers for Disease Control and Prevention guidelines.
Ma et al. 2020	The study verified a simple decontamination measure suitable to most people for reuse of MMs and N95Ms.	Steam on boiling water	Avian coronavirus of infectious bronchitis virus H120	Vaccine strain of avian infectious bronchitis virus H120	RT-PCR	The study observes that if a mask will be reused, it should be doffed without touching its surface, and the doffed mask should be put directly into a plastic bag or stainless steel box for steam and avoiding contamination of the surface of other items. They also presume that the masks can be used for up to seven or ten days, if they keep clean and fitted, and have not been damaged by other factors. Therefore, this study is valuable for solving the great shortage of masks in many countries for fighting the COVID-19 pandemic. It can also minimize unnecessary waste and protect the environment for discarding reusable masks.
Ou et al. 2020	To evaluate the filtration performance of three commercially available and two alternative face mask and respirator materials after selected decontamination treatments	Ultraviolet germicidal irradiation, oven heating method (dry heat as 77C), steam heat treatment method; isopropanol (IPA) (soaking or spraying)	–	–	–	Both IPA soaking and spraying removed most electrostatic charges on all four electret materials (three commercial and one alternative), causing significant deterioration of filtration efficiency to unacceptable level. The other non-electret alternative material sustained its N95-grade performance after both IPA soaking and spraying treatments, demonstrating the possible application of IPA disinfection for non-electret alternative respirator/mask materials. UVGI preserved the filtration of all three commercially available respirator/mask materials after up to 10 treatments, suggesting it can be a possible decontamination method for hospital and clinic use without compromising respirator/mask performance. Between the two heat treatment methods tested, dry heat showed better compatibility with electret material by sustaining both filtration efficiency and fit (tested on commercial respirator only), although adding moisture was reported in favor of virus inactivation. Heat treatment is easily accessible method for general publics to implement at home, while it is recommended to maintain the moisture level below saturation.
Pascoe et al. 2020	The study aimed to establish effective protocols for the decontamination of respirators using dry heat or microwavegenerated steam	70oC dry heat and microwave generated steam	Staphylococcus aureus	Staphylococcus aureus	CFU	Authors found that microwave generated steam was potentially effective in decontaminating N95-type respirators, whilst dry heat was potentially effective for the reprocessing of N95-type respirators, providing possible safe reprocessing methods should the procurement of unused PPE fail.
Saini et al. 2020	The study highlights the utility of vaporized hydrogen peroxide-based strategy to ensure a safe and effective disinfection of PPEs for selective reuse.	Various concentrations of hydrogen peroxide by diluting the hydrogen peroxide stock to 6, 8 and 10% with distilled water	B. stearothermophilus, saprophytic, non-virulent, recombinant laboratory strains of E. coli and M. smegmatis	Not reported	CFU	Vaporised hydrogen peroxide-based disinfection method is a suitable process to ensure a safe and effective reuse of PPEs
Simmons et al. 2020	Article reports the effectiveness of a pulsed xenon ultraviolet disinfection system in reducing the load of SARSCoV- 2 on hard surfaces and N95 respirators	Pulsed Xenon Ultraviolet	The SARS-CoV-2 working stock was generated from isolate USA-WA1/2020	The SARS-CoV-2 working stock was generated from isolate USA-WA1/2020	Plaque assay	Authors found that Pulsed Xenon Ultraviolet significantly reduces SARS-CoV-2 on hard surfaces and N95 respirators
Vo et al. 2020	The aim of the present study was to develop a test system to evaluate the effectiveness of procedures for decontamination of respirators contaminated with viral droplets	Sodium hypochlorite and UV irradiation	MS2 virus, Escherichia coli	–	The study for analazing the efficacy of decontamination(ED) for MS2 of sodium hypochlorite decontamination, were the number of viable MS2 phage was determined by a plaque assay, was calculated by determining the log reduction as follows: ED log (N°/N), where N° is the mean number of viable MS2 phage applied to the control coupons and N is the number of viable MS2 phage recovered from test coupons after decontamination. The efficacy of UV decontamination for viable MS2 was calculated as described for the efficacy of sodium hypochlorite decontamination.	The results demonstrated that the size range of the droplets was 0.5–15 μ and that the majority of the droplet particles were between 0.74 and 3.5 μ in diameter. Treatment with sodium hypochlorite (bleach) was an efficient chemical decontamination method for MS2 virus loaded onto FFRs. Treatment with low sodium hypochlorite doses (2.75–5.50 mg/liter) resulted in approximately 3- to 4-log reductions in the levels of MS2 coliphage, while treatment with higher sodium hypochlorite doses (8.25 mg/liter) resulted in no detectable MS2 virus. UV irradiation was also demonstrated to be an efficient physical decontamination treatment for MS2 virus. Treatment with low UV irradiation doses (4.32–5.76 J/cm2) resulted in 3.00- to 3.16-log reductions in the levels of MS2 coliphage, while treatment with higher UV irradiation doses (7.20 J/cm2) resulted in no detectable MS2 virus.
Wang et al. 2020	Authors report a approach for the decontamination of masks using hot water at a temperature greater than 56o C for 30 min	Soaked in hot water at a temperature greater than 56o C for 30 min. The masks were then dried using an ordinary household hair dryer to recharge the masks with electrostatic charge to recover their filtration function	–	–	–	By soaking the masks in hot water at greater than 56 C for 30 min, viruses are killed and the dirt on the surface of the masks is removed. After the mask is dried with a standard hair dryer for 10 min, the static electricity of the surgical mask can be recovered to 90 % of the level of a newmask.
Woolverton et al. 2020	The study tested the ability of food-grade silica bead packets to accelerate moisture removal from N95 s during 24 -h time periods.	Use of food-grade silica bead packets	–	–	–	The study does demonstrate that silica can be used to desiccate an N95, removing moisture that may be generated during the decontamination process using an autoclave or ionized/vaporized hydrogen peroxide, thus enabling the N95 to be more rapidly returned for use.
Xiang et al. 2020	The study aimed to optimize the temperature of dry heat pasteurization to achieve efficient decontamination of masks	Dry heat at 60 °C and 70 °C for 1 h	Escherichia coli (ATCC25922), Staphylococcus aureus (ATCC25923), Pseudomonas aeruginosa (ATCC27853), Klebsiella pneumonia (ATCC70063), Acinetobacter baumannii (ATCC17978), Corynebacterium pseudodiphtheria (ATCC10701), and Candida albicans (ATCC10231).	H1N1 virus	Culture infective dose assay	"Dry heat at 60 °C and 70 °C for 1 h can ensure the decontamination of surgical face masks and N95 respirator while maintaining their filtering efficiency and shape for up to at least three rounds of dry heat".
Zulauf et al. 2020	Authors described development and evaluation of a simple microwave steam decontamination protocol	Microwave steam	MS2 phage	MS2 phage	Plaque assay	Microwave-generated steam provides a valuable means of effective decontamination and reuse of N95 respirators.
LETTERS
Burkhart et al. 2020	The sterilization process with the SoClean system is with activated oxygen (ozone)	Vaporized hydrogen peroxide, ethylene oxide, activated oxygen (often referred to as O3 or ozone)	–	–	–	The SoClean CPAP Sanitizer is a viable method for sterilizing against coronavirus, and therefore, reusing n95 masks or any cloth mask can be achieved with this method.
Carrillo et al. 2020	Letter reporting an in vitro study assessing the use of Immediate-use steam sterilization for decontamination of N95 respirators.	Immediate-use steam sterilization (IUSS), using a Steris Amsco Evolution HC1500 PreVac Steam Sterilizer autoclave	It was tested sterelization and it was not tested specific organism		TSI PortaCount Respirator Fit Tester	The data of this study provides a valid base for the use of the IUSS method for decontamination of N95 masks to prevent the spread of the virus SARS-Cov-2 to health care workers
Cheng et al. 2020	Letter reporting an in vitro study assessing the use of Ionized H2O2 for decontamination of N95 respirators.	Ionized H2O2 (iHP)	H1N1	H1N1 (enveloped RNA virus that has similar virological characteristics as coronaviruses)	The virus were enluted from N95 respirators for viral culture in MDCK cells. Cytophatic changes of MDCK cells were observed daily for 7 days by light microscopy and the samples were subcultured again on MDCK cells for a further seven days. It was preformed immunofluorescence staining to detect influeza A antigen.	This experiment showed that iHP could kill influenza A virus at moderate to high levels of inoculum. And the level of H2O2 on the inner surface of N95 respirators was 0.6 ppm (below the safety limit of <1 ppm) at 2 h and undetectable at 3 h. The speed of H2O2 release from N95 respirators may be variable and affected by the air current.
Hamzavi et al. 2020	Letter proposing a possible repurposing of phototherapy devices, including these UVB units, to serve as a platform for UVC germicidal disinfection.	Ultraviolet germicidal irradiation (UVGI)	SARS-CoV	–	–	UVGI and repurposing phototherapy devices could be the best practical solution at this time.
Kobayashi et al. 2020	Letter showing an overview of national regulatory authority recommendations.	Dry heat in a drying cabinet at 65–70 °C (Germany), vaporous hydrogen peroxide (Netherlands, Europe, and the United States), ultraviolet germicidal irradiation and moist heat (Europe and the United States)	–	–	–	The Ministry of Labor and Social Affairs of Germany described the recommended decontamination method for N95 respirators in detail (ie, dry heat at 65–70 °C in a drying cabinet for 30 min). On the other hand, up to 60% of the screened countries did not report any recommendations for extended use or reuse or decontamination of N95 respirators.
Li et al. 2020 [[69]]	Letter discussing an in vitro study that tested Rice Cooker-Steamer for Decontamination of Cloth and Surgical Face Masks and N95 Respirators.	Ultraviolet light treatment, hydrogen peroxide vapor, moist or dry heat, steam treatment via rice cooker steam	Clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA) and thenonenveloped, single-stranded RNA virus bacteriophage MS2	Unclear	Calculation of colony-forming units (CFU) or plaque-forming units (PFU) reduction.	The results of the study demonstrate that steam treatment using a rice cooker-steamer is effective for decontamination of face masks and N95 respirators. Investigations of moist heat are also needed as 20 min of exposure to moist heat at 65 °C has been reported to be effective with minimal adverse effects on respirator performance.
Narla et al. 2020	Letter discussing the importance of the minimum dosage necessary for UVC decontamination of N95 respirators during the COVID-19 pandemic.	Ultraviolet C (UVC)	influenza A (H1N1), avian influenza A virus (H5N1), influenza A (H7N9) A/Anhui/1/2013, influenza A (H7N9) A/Shanghai/1/2013SARS-CoV-2, SARS-CoV and MERS-CoV	–	–	The study states that it should also be emphasized that there are significant limitations to UVC decontamination methods due to the variety of respirators used in healthcare facilities. Consequently, this process should only be considered as a risk mitigation effort during severe shortage of N95 respirators but is one of the most effective and best studied options available to front-line personnel.
Ozog et al. 2020	Letter discussing the Importance of Fit-Testing in Decontamination of N95 1 Respirators	Ultraviolet germicidal irradiation (UVGI), hydrogen peroxide vaporization, microwave generated steaming and dry heating	The study discussed about fit-testing performance collected for the different respirator models treated with UVGI.			The data of this study strongly indicates that to protect the safety of the N95 respirator user, fit-testing after decontamination must be done each time a new model is introduced to a healthcare system. This has significant safety implications as varied decontamination methods are being used by different institutions.
Schwartz et al. 2020.	Authors shared processes of Decontamination and Reuse of N95 Respirators with Hydrogen Peroxide Vapor	Hydrogen peroxide vapor	6-log biological indicators (Geobacillus stearothermophilus spores)	Not reported	The study talks about a quality assurance (QA) step, after complete aeration, to ensure both qualitative and quantitative degradation has not occurred, ensuring that there was no physical or erformance degradation. Also, a standardized quantitative fit testing was preformed to ensure the integrity of the respirators is maintained over many decontamination cycles. In addition, we validated the efficacy of the decontamination process by using 9 individual 6-log biological indicators (Geobacillus stearothermophilus spores).	Using hydrogen peroxide vapor is a proven method of decontamination. Authors believe that decontamination of N95 respirators with hydrogen peroxide vapor is one such solution that affords us better ability to protect our health care workers as we continue to tackle this monumental issue.
OTHERS
Garg and Garg, 2020	Unclear	UV irradiation, vaporous hydrogen peroxide, moist heat, and microwave-generated steam	–	–	–	At present, it is unclear if these processes render the masks vulnerable and new research will address questions related to filtration efficiency and mask deformation.
Grossman et al. 2020	The objective of the paper was to present a just-in-time process created for N95 respirator disinfection using VHP that allows the individual healthcare worker to retain his or her own respirator.	Vaporized hydrogen peroxide	N95 respirators used by health care workers	–	After each disinfection cycle, biologic indicators were transferred to commercially available trypticase soy broth (TSB) with a color indicator (Mesa Labs and Steris), and incubated at 56oC for at least 24 h. A negative result indicated a successful disinfection cycle.	The study shows that a reproducible and scalable process for implementing N95 respirator disinfection within a large academic hospital and healthcare system is achievable through multidisciplinary collaboration and rapid adaptation in the setting of the COVID-19 pandemic and critical N95 respirator shortages.
Juang and Tsai, 2020	Unclear	Mask rotation (1 Mask Every 3–4 Days), Heat (at 70oC (158oF) for 60 M in.; Boil (for 5 M in., Steam Clean (at 125oC (257oF) for 5 M in.	–	–	–	The author present these methods and he suggest that where there are N95 respirator shortages around the world clinicians consider using one or more of these methods as a bridge until sufficient N95 masks are available.
le Roux and Dramowski, 2020	The authors discusses the available PPE preservation strategies and addresses the issue of decontamination and re-use of N95 respirators as a last-resort strategy for critical shortages during the pandemic	Hydrogen peroxide vapour, UVGI (ultraviolet germicidal irradiation), Microwave (generated steam), Methods not currently endorsed owing to limited evidence (Moist heat incubation; Mask rotation; Ozone; liquid hydrogen peroxide/hydrogen peroxide plasma; dry heat; 70 % isopropyl alcohol; autoclave; soap; dry microwave irradiation; gamma irradiation; bleach; ethylene oxide)	–	–	–	Decontamination of N95 respirators should only be consider as a last resort to ensure a supply of N95 respirators for healthcare workers performing aerosol-generating procedures on patients with suspected/confirmed COVID-19.
Nogee and Tomassoni, 2020	Authors propose investigating the use of ultraviolet germicidal irradiation to sterilize masks of SARS-CoV-2 for safer reuse.	Ultraviolet germicidal irradiation (UVGI), ethylene oxide and vaporized hydrogen peroxide	Influenza virus, SARS-CoV-2 and SARS-CoV	–	–	The study observes that although further work will be needed to determine dosages of UVGI to effectively sterilize SARS-CoV-2 contaminated FFRs, UVGI provides a potential avenue for greatly extending the limited FFR supply in the face of the ongoing COVID-19 pandemic in a simple, cost-effective, and rapidly deployable manner. Hospitals and healthcare facilities should consider immediate implementation of collection programs for used FFRs in anticipation of near-future sterilization and reuse programs.
Perkins et al. 2020	Describe the development of a process that began in late February 2020 for selecting and implementing the use of hydrogen peroxide vapor (HPV) as viable method to reprocess N95 respirators	Hydrogen peroxide vapor (HPV)	N95 filtering facepiece respirators used by healthcare personnel		Culture and visual inspection	The data of the study presented in this article are meant to serve as an information sharing tool for other institutions who may wish to set up such processes, particularly for those who do not already have specific HPV chambers already in place. The two most important lessons learned from our experience are: (1) develop an adequate reserve of PPE for efficiently implementing the reprocessing workflow and (2) locate a suitable environment for the HPV decontamination procedure, such as an operating room, which has the pre-existing conditions required for conducting the HPV decontamination process.
Prakash et al. 2020	The article proposed the validation and eventual use of gamma irradiation, to disinfect FFRs in bulk.	Gamma irradiation	H1N1 influenza, MS2 virus and SARS-CoV-2	SARS-CoV-2	–	The data on re-sterilization strategies are scarce and do not address major concerns that allow for mass application. It needs to be stressed, in no uncertain terms, that re-sterilization techniques, such as gamma irradiation in this context need validation which if performed on a war footing, may just be of vital importance in these times.
Rowan and Laffey, 2020	Article discussed concern regarding the shortage in supply chain of critical one-time-use personal and protective equipment.	Vaporised hydrogen peroxide, UV irradiation and High-level liquid disinfection (Actichlor+), Ethylene oxide (Eto) and pulsed UV technology (PUV)	–	–	–	The article observes that the best evidence suggest that preferred candidate methods for meeting this gap appears to be use of vaporized hydrogen peroxide (VHP) and UV irradiation technologies.
Zhong et al. 2020	Authors report a plasmonic photothermal and superhydrophobic coating on N95 respirators	Deposit silver nanoparticles	–	–	–	The presence of the silver nanoparticles can provide additional protection via the silver ion’s disinfection toward microbes.

Findings based on the article reporting.