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Safety in the practice of decontaminating filtering facepiece respirators: A systematic review

Published:December 03, 2020DOI:https://doi.org/10.1016/j.ajic.2020.11.022

      Highlights

      • Scarcity of material resources promotes the reuse of N95 or higher filtration masks.
      • When reuse is inevitable automated sterilization methods are safer options.
      • Filtration, chemical residuals, and Microbiological assessment must be evaluated.

      Background

      Considering the new SARS-CoV-2 pandemic and the potential scarcity of material resources, the reuse of personal protective equipment such as filtering facepiece respirators (FFRs) for N95 filtering or higher is being discussed, mainly regarding the effectiveness and safety of cleaning, disinfection and sterilization processes.

      Aim

      To analyze the available evidence in the literature on the safety in processing FFRs.

      Methods

      A systematic review conducted by searching for studies in the following databases: PubMed, CINAHL, LILACS, CENTRAL, EMBASE, Web of Science, and Scopus.

      Results

      Forty studies were included in this review. The disinfectant/sterilizing agents most frequently tested at different concentrations and exposure periods were ultraviolet irradiation, vaporized hydrogen peroxide and steam sterilization. Microbial reduction was assessed in 21 (52.5%) studies. The only disinfectants/sterilizers that did not caused degradation of the material-integrity were alcohol, electric cooker, ethylene oxide, and peracetic acid fogging. Exposure to ultraviolet irradiation or microwave generated-steam resulted in a nonsignificant reduction in filter performance.

      Conclusion

      There is a complex relationship between the FFR raw materials and the cycle conditions of the decontamination methods, evidencing the need for validating FFRs by models and manufacturers, as well as the process. Some methods may require additional tests to demonstrate the safety of FFRs for use due to toxicity.

      Key Words

      INTRODUCTION

      Material resources during public health emergencies may be restricted and the processing of personal protective equipment such as filtering facepiece respirators (FFRs) for N95 filtering or higher may be placed on the agenda.
      • Brady TM
      • Strauch AL
      • Almaguer CM
      • et al.
      Transfer of bacteriophage MS2 and fluorescein from N95 filtering facepiece respirators to hands: measuring fomite potential.
      Thus, health services have considered processing to reuse them in order to mitigate a possible shortage of respiratory protection devices.
      In addition to the recommendation for prolonged use, decontamination followed by the reuse of FFR has been suggested as a contingency capacity strategy by the Centers for Disease Control and Prevention to conserve available supplies during a pandemic.
      Centers for Disease Control and Prevention
      Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare Settings.
      ,
      Centers for Disease Control and Prevention
      Decontamination and Reuse of Filtering Facepiece Respirators.
      This body emphasizes that FFRs must not be decontaminated to be reused as a standard procedure, as such practice is inconsistent with the approval of product use since it is not a requirement to support cleaning and disinfection; however, in a critical crisis situation it is an option to be considered.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      On the other hand, a recent publication by the US Food and Drug Administration (FDA) authorized the use of hydrogen peroxide-based equipment to sterilize N95 masks on an emergency basis, which would allow the reuse of each respirator up to 50 times.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      However, parameters such as biocidal efficacy, FFR functionality maintenance in relation to filtration performance and proper adjustment of the equipment to the face and presence of residual toxicity must be evaluated in order to consider the processing of the material a valid strategy to be implemented.
      Centers for Disease Control and Prevention
      Decontamination and Reuse of Filtering Facepiece Respirators.
      ,
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      Considering the new SARS-CoV-2 pandemic and the scarcity of data regarding the effectiveness of the cleaning, disinfection and sterilization processes of this equipment, the present study aims to analyze the evidence available in the literature on the safety of processing N95 or higher filtration masks.

      METHODS

      A systematic review following the recommendations of the PRISMA declaration (Preferred Reporting Items for Systematic Reviews and Meta-analyses) was used
      • Liberati A
      • Altman DG
      • Tetzlaff J
      • et al.
      The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: explanation and elaboration.
      and the protocol of the project has been submitted on PROSPERO (Registration-No: CRD42020185605). The guiding question of the present systematic review was: Are disposable processed N95 or higher filtration FFRs safe for professional use regarding their integrity, filtration, and contamination?

      Data sources and search strategy

      The databases selected to search for the primary studies included in this review were: PubMed/Medline, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS), Cochrane Central Register of Controlled Trials (CENTRAL), Excerpta Medica Database (EMBASE), Web of Science, and Scopus, from their conception until November 5, 2020. Controlled descriptors from each database were searched, as well as the following keywords: “masks,” “N95,” “n-95, ” “n95 filtering facepiece respirator,” “pff2,” “respiratory protective devices,” “respiratory protection device,” “disinfection,” “instrument sterilization,” “sterilizations,” “decontamination,” “medical device contamination,” “equipment reuse,” “reuse,” “reusable,” and “sanitization.”
      For the location of publications, controlled descriptors, and keywords were delimited and combined (Supplementary Material 1). Gray literature (dissertations, government regulatory documents, and technical notes), including references cited in the included articles, published research reports, and preprint articles were also analyzed.

      Study inclusion and exclusion criteria

      Experimental studies, published in English, Spanish, or Portuguese, which evaluated decontamination and/or sterilization of FFRs were included with or without prior cleaning according to the outcomes of integrity, filtration and microbiological safety. Articles referring to respirators for industrial use or reusable respirators (dust respirators, plastic respirators, or elastomeric respirators), that submitted only fragments of FFRs to decontamination processes, letters to editor, research letters, and opinion articles not guided by scientific research were excluded.

      Selection of studies

      Two reviewers (authors C.S.L and J.R.G.) independently assessed the title and abstracts of potentially relevant studies using the selection criteria. A third author (V.B.P.) was consulted if it was unclear from the title and abstract whether a study met the inclusion criteria or if there was a disagreement over eligibility. The full text of articles considered as eligible were examined.

      Data extraction

      All data were extracted by 2 independent pairs of investigators (pair A: authors L.R.M. and G.A.A.M; pair B: authors R.A.O. and R.Q.S.) using a standardized form, and data were checked for integrity and accuracy by 2 other reviewers (authors C.S.L and J.R.G.). The data extracted from included studies were related to the following characteristics: title, journal of publication, year of publication, country of origin, language of publication; study design: type of study, fund source, mask type and model, manufacturer, pathogen load, and method of mask contamination, when available, and number of samples used; decontamination/sterilization procedures: Method of mask treatment, presence of cleaning process before the decontamination procedures, exposure time, frequency of exposure to the treatment, concentration/intensity of disinfectant agents; and the outcomes: penetration (absolute percentage, change relative to baseline), absolute and relative change in pathogen counting, observations of physical degradation and/or odor. When there were disagreements between investigators during data process extraction, another author was consulted (V.B.P).

      Risk of bias and quality of evidence assessments

      The risk of bias and the quality of evidence assessments were not evaluated due to the unavailability of validated tools for evaluating experimental laboratory studies.

      Data synthesis

      Due to the heterogeneity of the studies included in this SR, the synthesis of the included studies is presented in a narrative overview.

      RESULTS

      A total of 3,536 articles were identified during the database search, with 4 more articles found in additional searches. After removing duplicates, 2,579 articles were evaluated using titles and abstracts, of which 2,504 were excluded. The full texts of 75 articles were revised according to the inclusion and exclusion criteria, with 35 being excluded because they evaluated sterilization processes only with fragments of FFR, surgical masks, elastomeric masks, or were characterized as opinion articles, letters to the editor or recommendations by experts.
      Thus, 40 studies for the qualitative synthesis of evidence remained in the review. The details of the study selection process are presented in the Figure 1.
      Fig 1
      Fig 1PRISMA Flow diagram of the study selection process.

      Studies’ characteristics

      All identified publications developed experimental laboratory studies. All included studies analyzed N95 model FFRs.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      • Mills D
      • Harnish DA
      • Lawrence C
      • Sandoval-Powers M
      • Heimbuch BK
      Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators.
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      • Vo E
      • Rengasamy S
      • Shaffer R
      Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      • Zhao Z
      • Zhang Z
      • Lanzarini-Lopes M
      • et al.
      Germicidal ultraviolet light does not damage or impede performance of N95 Masks upon multiple uses.
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      • Fisher E
      • Williams J
      • Shaffer R
      The effect of soil accumulation on multiple decontamination processing of N95 filtering facepiece respirator coupons using physical methods.
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      • Czubryt MP
      • Stecy T
      • Popke E
      • et al.
      N95 mask reuse in a major urban hospital: COVID-19 response process and procedure.
      • Daeschler SC
      • Manson N
      • Joachim K
      • et al.
      Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function.
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      • Ibáñez-Cervantes G
      • Bravata-Alcántara JC
      • Nájera-Cortés AS
      • et al.
      Disinfection of N95 masks artificially contaminated with SARS-CoV-2 and ESKAPE bacteria using hydrogen peroxide plasma: impact on the reutilization of disposable devices.
      • Jatta M
      • Kiefer C
      • Patolia H
      • et al.
      N95 reprocessing by low temperature sterilization with 59% vaporized hydrogen peroxide during the 2020 COVID-19 pandemic.
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.
      • Lieu A
      • Mah J
      • Zanichelli V
      • Exantus RC
      • Longtin Y
      Impact of extended use and decontamination with vaporized hydrogen peroxide on N95 respirator fit.
      • Lin T-H
      • Tseng C-C
      • Huang Y-L
      • Lin H-C
      • Lai C-Y
      • Lee S-A
      Effectiveness of N95 facepiece respirators in filtering aerosol following storage and sterilization.
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      • Ozog DM
      • Sexton JZ
      • Narla S
      • et al.
      The effect of ultraviolet C radiation against different N95 respirators inoculated with SARS-CoV-2.
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      • Purschke M
      • Elsamaloty M
      • Wilde JP
      • et al.
      Construction and validation of UV-C decontamination cabinets for filtering facepiece respirators.
      • Widmer AF
      • Richner G.
      Proposal for a en 149 acceptable reprocessing method for FFP2 respirators in times of severe shortage.
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      Additionally, 1 investigation employed FFR P100,
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      another used PFF-3,
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      and 7 also used surgical masks.
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      ,
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      • Zhao Z
      • Zhang Z
      • Lanzarini-Lopes M
      • et al.
      Germicidal ultraviolet light does not damage or impede performance of N95 Masks upon multiple uses.
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      ,
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      More than half of the studies included in this review received funding.
      Supplementary Material 2 presents the results of the studies according to the microbiological analysis conducted, the FFR integrity (including the facepiece and its components), filtering capacity, and residual presence of the disinfectant/sterilizing agent and funding source.
      The most frequent disinfectant/sterilizing agents tested at different concentrations and exposure periods by the included studies were ultraviolet irradiation, vaporized hydrogen peroxide (VHP), steam sterilization (autoclave), sodium hypochlorite, microwave-generated steam, among others (Table 1). In addition to these, methods which are not traditionally used in environments aimed at disinfection or sterilization were also tested such as electric cookers and microwave ovens (Table 1).
      Table 1Methods of disinfection/sterilization methods analyzed accordingly the included studies. Brazil, 2020
      Cleaning/disinfection/sterilization methodsViscusi et al. (2007)
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      Vo et al. (2009)
      • Vo E
      • Rengasamy S
      • Shaffer R
      Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.
      Viscusi et al. (2009)
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      Bergman et al. (2010)
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      Salter et al (2010)
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      Fisher et al.,, 2010
      • Fisher E
      • Williams J
      • Shaffer R
      The effect of soil accumulation on multiple decontamination processing of N95 filtering facepiece respirator coupons using physical methods.
      Fisher et al. (2011)
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      Viscusi et al. (2011)
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      Heimbuch et al. (2011)
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      Lore et al. (2012)
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      Heimbuch et al. (2014)
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      Lin et al. (2017)
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      Mills et al. (2018)
      • Mills D
      • Harnish DA
      • Lawrence C
      • Sandoval-Powers M
      • Heimbuch BK
      Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators.
      Lin et al. (2018)
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      Kumar et al. (2020)
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      Battelle et al. 2020)

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      Alijabo et al. (2020)
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      Andereg et al. (2020)
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.
      Bopp et al. (2020)
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      Cadnum et al. (2020)
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.
      Celina et al. (2020)
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      Czubryt et al. (2020)
      • Czubryt MP
      • Stecy T
      • Popke E
      • et al.
      N95 mask reuse in a major urban hospital: COVID-19 response process and procedure.
      Daeschler et al. (2020)
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      Grinshpun et al. (2020)
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      Harskamp et al. (2020)
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      Ibez-Cervantes, 2020)
      • Ibáñez-Cervantes G
      • Bravata-Alcántara JC
      • Nájera-Cortés AS
      • et al.
      Disinfection of N95 masks artificially contaminated with SARS-CoV-2 and ESKAPE bacteria using hydrogen peroxide plasma: impact on the reutilization of disposable devices.
      Jatta et al. (2020)
      • Jatta M
      • Kiefer C
      • Patolia H
      • et al.
      N95 reprocessing by low temperature sterilization with 59% vaporized hydrogen peroxide during the 2020 COVID-19 pandemic.
      Kim et al. (2020)
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.
      Lieu et al. (2020)
      • Lieu A
      • Mah J
      • Zanichelli V
      • Exantus RC
      • Longtin Y
      Impact of extended use and decontamination with vaporized hydrogen peroxide on N95 respirator fit.
      Lin et al. (2020)
      • Lin T-H
      • Tseng C-C
      • Huang Y-L
      • Lin H-C
      • Lai C-Y
      • Lee S-A
      Effectiveness of N95 facepiece respirators in filtering aerosol following storage and sterilization.
      Ludwig et al. (2020)
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.
      Ma et al. (2020)
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.
      Oh et al. (2020)
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      Ozog et al. (2020)
      • Ozog DM
      • Sexton JZ
      • Narla S
      • et al.
      The effect of ultraviolet C radiation against different N95 respirators inoculated with SARS-CoV-2.
      Pascoe et al. (2020)
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      Purschke et al. (2020)
      • Purschke M
      • Elsamaloty M
      • Wilde JP
      • et al.
      Construction and validation of UV-C decontamination cabinets for filtering facepiece respirators.
      Widmer et al. (2020)
      • Widmer AF
      • Richner G.
      Proposal for a en 149 acceptable reprocessing method for FFP2 respirators in times of severe shortage.
      Xiang et al. (2020)
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      Zhao et al. (2020)
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      Zulauf et al. (2020)
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      Total
      UV-C/AXXXXXXXXXXXXXXXX16
      VHPXXXXXXXXXXX11
      Steam sterilization (Autoclave 121°C)XXXXXXXXXXX11
      Sodium hypochloriteXXXXXXXX8
      Microwave-generated steamXXXXXXXX8
      70% Ethanol/70% Isopropyl/100% IsopropylXXXXXX6
      Moist heatXXXXXX6
      Dry heatXXXXX5
      EtOXXXXX5
      HPGPXXX3
      Liquid hydrogen peroxideXXX



      3
      Electric cookerXXX3
      MicrowaveXX2
      DMDOX1
      PasteurizationX1
      Soap and waterX1
      Antiseptic wipesX1
      Peracetic acid dry fogging systemX

      1
      High-level disinfection cabinet (Altapure, Mequon: peracetic acid, hydrogen peroxide, acetic acid)X1
      1% Pine-Sol and 1% benzalkonium chloride in Ethanol 70%X1
      Gamma IrradiationX1
      HP = vaporized hydrogen peroxide; HPGP = hydrogen peroxide gas plasma.

      Microbiological assessment

      The microbiological survival was assessed in 21 studies.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      ,
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      ,
      • Mills D
      • Harnish DA
      • Lawrence C
      • Sandoval-Powers M
      • Heimbuch BK
      Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators.
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      • Vo E
      • Rengasamy S
      • Shaffer R
      Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.
      ,
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      ,
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Fisher E
      • Williams J
      • Shaffer R
      The effect of soil accumulation on multiple decontamination processing of N95 filtering facepiece respirator coupons using physical methods.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      ,
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.
      ,
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      ,
      • Ibáñez-Cervantes G
      • Bravata-Alcántara JC
      • Nájera-Cortés AS
      • et al.
      Disinfection of N95 masks artificially contaminated with SARS-CoV-2 and ESKAPE bacteria using hydrogen peroxide plasma: impact on the reutilization of disposable devices.
      ,
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.
      ,
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      • Ozog DM
      • Sexton JZ
      • Narla S
      • et al.
      The effect of ultraviolet C radiation against different N95 respirators inoculated with SARS-CoV-2.
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      • Purschke M
      • Elsamaloty M
      • Wilde JP
      • et al.
      Construction and validation of UV-C decontamination cabinets for filtering facepiece respirators.
      ,
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      Seven studies proceeded the test using viruses such as bacteriophages,
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.
      ,
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      coronavirus,
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      ,
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.
      ,
      • Ozog DM
      • Sexton JZ
      • Narla S
      • et al.
      The effect of ultraviolet C radiation against different N95 respirators inoculated with SARS-CoV-2.
      H1N1,
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      adenovirus, and gastroenteritis virus.
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      Five studies conducted the tests using only one bacterial specimens.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      ,
      • Ibáñez-Cervantes G
      • Bravata-Alcántara JC
      • Nájera-Cortés AS
      • et al.
      Disinfection of N95 masks artificially contaminated with SARS-CoV-2 and ESKAPE bacteria using hydrogen peroxide plasma: impact on the reutilization of disposable devices.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      ,
      • Purschke M
      • Elsamaloty M
      • Wilde JP
      • et al.
      Construction and validation of UV-C decontamination cabinets for filtering facepiece respirators.
      From all 40 studies included in this review, only 6 evaluated 3 mainly parameters considered in this review, eaning microbial load, integrity, and filtration.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      ,
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      ,
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      A research report not published in a scientific journal that used Hydrogen Peroxide Vapor (HPV).

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      The report recommends that further tests should be carried out with other models/brands of N95 FFR, because different respirators may have filter media which are affected in different ways by the sterilizing agent. In addition, they suggest tests to demonstrate the effectiveness of the HPV decontamination cycle against other microorganisms of interest in the community. In relation to the functionality tests, the amount of leakage in the FFR was measured during the light respiratory flow simulation (20 L/min) on a mannequin, having not been affected by up to 20 cycles.

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      Other 5 studies used high temperature (heat). Steam sterilization resulted in successful inactivation of heat-resistant bacterial spores in 2 FFR models, and bacterial growth in samples of another model of FFR.
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      The electric cooker method demonstrated higher inactivation efficacy of viruses inoculated on the hydrophilic surface (on the user's surface) compared to that on the hydrophobic surface (outside), and the final infectivity was below the detection limit of the plaque assay.
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      Dry heat and microwave-generated steam were successful in achieving the target of >4 log10 reduction in S. aureus viability
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      and killed 7 bacteria strains as well as inactivated the H1N1 virus.
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      Also, in another study that used microwave generated steam a 6-log10 plaque-forming was detected.
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.

      Integrity assessment

      The preservation of material integrity was assessed in 22 studies (55.0%).

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      • Zhao Z
      • Zhang Z
      • Lanzarini-Lopes M
      • et al.
      Germicidal ultraviolet light does not damage or impede performance of N95 Masks upon multiple uses.
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.
      ,
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      • Czubryt MP
      • Stecy T
      • Popke E
      • et al.
      N95 mask reuse in a major urban hospital: COVID-19 response process and procedure.
      • Daeschler SC
      • Manson N
      • Joachim K
      • et al.
      Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function.
      ,
      • Jatta M
      • Kiefer C
      • Patolia H
      • et al.
      N95 reprocessing by low temperature sterilization with 59% vaporized hydrogen peroxide during the 2020 COVID-19 pandemic.
      ,
      • Lieu A
      • Mah J
      • Zanichelli V
      • Exantus RC
      • Longtin Y
      Impact of extended use and decontamination with vaporized hydrogen peroxide on N95 respirator fit.
      ,
      • Oh C
      • Araud E
      • Puthussery J V.
      • et al.
      Dry heat as a decontamination method for n95 respirator reuse.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      ,
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      It can be observed that the use of hydrogen peroxide,

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      ,
      • Ibáñez-Cervantes G
      • Bravata-Alcántara JC
      • Nájera-Cortés AS
      • et al.
      Disinfection of N95 masks artificially contaminated with SARS-CoV-2 and ESKAPE bacteria using hydrogen peroxide plasma: impact on the reutilization of disposable devices.
      ,
      • Lieu A
      • Mah J
      • Zanichelli V
      • Exantus RC
      • Longtin Y
      Impact of extended use and decontamination with vaporized hydrogen peroxide on N95 respirator fit.
      especially Hydrogen Peroxide Gas Plasma,

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      and high-temperature methods
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      ,
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      ,
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.
      ,
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      were strongly associated with integrity degradation. Sodium hypochlorite also damaged the FFRs, causing stains, discoloration, dissolution of the nose seal comfort pad, oxidation, and stiffening of the filter and elastic
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      (Table 2).
      Table 2Association between disinfection/sterilization methods analyzed by studies and damage to integrity and filtration, and the presence of chemical and microbial residues on FFR. Brazil, 2020
      Cleaning/disinfection/ sterilization methodExposure timeMicrobial residueDamage integrityFiltration damageChemical residue/Odor
      Liquids (immersion)
      Alcohol

      70% Ethanol
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      ,
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      ,
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.


      70% Isopropyl
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      100% Isopropyl
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.


      Isopropyl (concentration not informed)
      • Lin T-H
      • Tseng C-C
      • Huang Y-L
      • Lin H-C
      • Lai C-Y
      • Lee S-A
      Effectiveness of N95 facepiece respirators in filtering aerosol following storage and sterilization.
      1 sec
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      1 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      10 min
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.


      120 min
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.


      Overnight
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.
      Survival of microorganisms up to 24 hours
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      Absence of structural damage
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      Filtration degradation:
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.


      - between 17.02% to 21.6% (N95 or KF94) and 0.41% to 0.80% (P100 FFR);
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.


      - N95: permeability for penetration of particles larger than 50 nm
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      -
      Soap and water 1g/L/ Tap water
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      2min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      20 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      --Filtration degradation:

      - N95: between 38.8 and 34.9%
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ;

      - P100: 0.01%-0.14% with soap water; unchanged with tap water
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      -
      Sodium hypochlorite

      0.525 and 5.25%
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      0.54%, 2.7% or 5.4%
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.


      0.60%
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.


      0.90%
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.


      5.00%
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.


      6.00%
      • Vo E
      • Rengasamy S
      • Shaffer R
      Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.
      ,
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.


      30 s
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      10 min
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      ,
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.


      30 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      Absence of microbial survival
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      or reduced microbial load
      • Vo E
      • Rengasamy S
      • Shaffer R
      Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.


      Mucin removal was < a log10 reduction factor of 1; a log10 reduction factor of 3-5
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      Varied damage:

      - Stiffening of the filter and elastic strips
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ;

      - Stained metallic nasal bands and alteration of brightness, oxidation of metallic parts
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      ;

      - Discoloration or dissolution of the nose seal comfort pad
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.


      - unspecified damage
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      Filtration degradation:

      - increased permeability for particle penetration below 5%
      • Heimbuch BK
      • Kinney K
      • Lumley AE
      • Harnish DA
      • Bergman M
      • Wander JD
      Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus.
      ,
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.


      Odor permanence
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      ,
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.


      8.25 mg/L: not detectable
      • Vo E
      • Rengasamy S
      • Shaffer R
      Development of a test system to evaluate procedures for decontamination of respirators containing viral droplets.
      Liquid hydrogen peroxide 3%
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      6%
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.


      30 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      -Varied damage:

      Oxidation of clamps to varying degrees
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      Filtration degradation
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      Average amount of oxidants ranging between values below the detection limit at 0.70 mg
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      DMDO
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      30 min
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      -Oxidation of metal parts
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      -Odor permanence
      • Salter WB
      • Kinney K
      • Wallace WH
      • Lumley AE
      • Heimbuch BK
      • Wander JD
      Analysis of residual chemicals on filtering facepiece respirators after decontamination.
      High temperature (heat)
      Steam sterilization (Autoclave)

      115°C
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.


      121°C
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      ,
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      ,
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      ,
      • Czubryt MP
      • Stecy T
      • Popke E
      • et al.
      N95 mask reuse in a major urban hospital: COVID-19 response process and procedure.
      ,
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.
      ,
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.
      ,
      • Lin T-H
      • Tseng C-C
      • Huang Y-L
      • Lin H-C
      • Lai C-Y
      • Lee S-A
      Effectiveness of N95 facepiece respirators in filtering aerosol following storage and sterilization.


      130°C
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      2 min
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.


      4 min
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.


      15 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      -
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      ,
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.
      ,
      • Lin T-H
      • Tseng C-C
      • Huang Y-L
      • Lin H-C
      • Lai C-Y
      • Lee S-A
      Effectiveness of N95 facepiece respirators in filtering aerosol following storage and sterilization.


      17 min
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.


      30 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      ,
      • Czubryt MP
      • Stecy T
      • Popke E
      • et al.
      N95 mask reuse in a major urban hospital: COVID-19 response process and procedure.
      ,
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.


      60 min
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.


      Absence of viable virus
      • Lin T-H
      • Tang F-C
      • Hung P-C
      • Hua Z-C
      • Lai C-Y
      Relative survival of bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods.
      ,
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.


      Bacterial growth in 1 of 4 models tested
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      Varied damage:

      - Absence of damage in 10 autoclave cycles on models 3M 1870, VFlex 1804S and AO Safety 1054S
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.


      - FFR-2: absence of damage
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.


      - Deformed, shrunk and rigid outer layer
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.


      - Significant variation was observed in the tensile force exerted by the straps of different FFR models
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.


      - 1860 model did not pass fit testing under any of the decontamination conditions
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.


      Models1805 passed fit testing for up to 3 decontamination cycles, at both 115°C and 121.1°C. Models 1870/1870 passed fit testing for up to

      3 decontamination cycles at both 115°C and 121.1°C but began

      to fail at 5 cycles at 121.1°C
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.


      - PFF-3: showed deformities and failed the seal check
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      20

      - FFR started failing after a second round of wear and sterilization
      • Czubryt MP
      • Stecy T
      • Popke E
      • et al.
      N95 mask reuse in a major urban hospital: COVID-19 response process and procedure.
      Variable degradation results:

      - From little change(10) to increased particle permeability, between 18.7 to 34.4% (according to the exposure time)

      United States Food and Drug Administration F. enforcement policy for face masks and respirators during the coronavirus disease (COVID-19) public health emergency (revised): guidance for industry and food and drug administration staff. 2020. p. 1–15. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-face-masks-and-respirators-during-coronavirus-disease-covid-19-public-health. Accessed June 10, 2020.

      ,
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Lin T-H
      • Chen C-C
      • Huang S-H
      • Kuo C-W
      • Lai C-Y
      • Lin W-Y
      Filter quality of electret masks in filtering 14.6-594 nm aerosol particles: effects of five decontamination methods.
      ,
      • Kumar A
      • Kasloff SB
      • Leung A
      • et al.
      N95 mask decontamination using standard hospital sterilization technologies.
      ,
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.


      - After second autoclaving, the filtration efficiency decreased to 81.69 ± 17.28%
      • Kim HP
      • Jo MS
      • Kim CH
      • Choi JS
      • Yu IJ
      Re-use of health masks after autoclaving.


      - Drop in filtration, especially masks with protein
      • Grinshpun SA
      • Yermakov M
      • Khodoun M
      Autoclave sterilization and ethanol treatment of re-used surgical masks and N95 respirators during COVID-19: impact on their performance and integrity.


      - Maintained the minimum requirement of 95% filtration efficiency
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.
      ,
      • Bopp NE
      • Bouyer DH
      • Gibbs CM
      • Nichols JE
      • Ntiforo CA
      • Grimaldo MA
      Multicycle autoclave decontamination of N95 filtering facepiece respirators.
      ,
      • Alijabo A
      • Mueller E
      • Azeez DA
      • Hore T
      • Jain A
      Gravity steam reprocessing in healthcare facilities for the reuse of N95 respirators.
      ,
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.


      - FFR-3: Filtration degradation
      • Harskamp RE
      • Van Straten B
      • Bouman J
      • et al.
      Reprocessing filtering facepiece respirators in primary care using medical autoclave: prospective, bench-to-bedside, single-centre study.


      - Maintained the minimum requirement of 95% filtration efficiency in some models of FFR
      • Lin T-H
      • Tseng C-C
      • Huang Y-L
      • Lin H-C
      • Lai C-Y
      • Lee S-A
      Effectiveness of N95 facepiece respirators in filtering aerosol following storage and sterilization.
      Moist heat

      65°C
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      ,
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      ,
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.


      70°C
      • Daeschler SC
      • Manson N
      • Joachim K
      • et al.
      Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function.


      70°C-85°C
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.


      Temperature not informed
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.
      20 min
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.


      30 min
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.


      40 min
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.


      60 min
      • Daeschler SC
      • Manson N
      • Joachim K
      • et al.
      Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function.
      ,
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.


      120 min
      • Ma QX
      • Shan H
      • Zhang CM
      • et al.
      Decontamination of face masks with steam for mask reuse in fighting the pandemic COVID-19: Experimental supports.


      3 h
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      Reduction of microbial load
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.


      No signs of deterioration
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Daeschler SC
      • Manson N
      • Joachim K
      • et al.
      Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function.


      Modification of seal and fit;

      delamination of the

      nose bridge foam
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.
      Non-significant reduction
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      ,
      • Anderegg L
      • Meisenhelder C
      • Ngooi CO
      • et al.
      A scalable method of applying heat and humidity for decontamination of n95 respirators during the covid-19 crisis.


      Significant reduction
      • Daeschler SC
      • Manson N
      • Joachim K
      • et al.
      Effect of moist heat reprocessing of N95 respirators on SARS-CoV-2 inactivation and respirator function.
      Odor permanence
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      Dry heat

      60°C
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.


      65°C
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.


      70°C
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      80°C
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.


      95°C
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.


      102°C
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.


      160°C
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      30 min
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.


      60 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.


      5-90 min
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      24 h
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      Had limited effectiveness against bacteriophages MS2 and Phi6 versus S. aureus <1 log10 PFU versus >4 log10 CFU
      • Cadnum JL
      • Li DF
      • Redmond SN
      • John AR
      • Pearlmutter B
      • Donskey CJ
      Effectiveness of ultraviolet-c light and a high-level disinfection cabinet for decontamination of n95 respirators.


      Reduction of microbial load
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Ludwig-Begall LF
      • Wielick C
      • Dams L
      • et al.
      The use of germicidal ultraviolet light, vaporized hydrogen peroxide and dry heat to decontaminate face masks and filtering respirators contaminated with a SARS-CoV-2 surrogate virus.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      Some evidence for onset of material weaknesses after 80°C exposure (deformations at the chin seal)
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      Filtration degradation: between 0.84% and 0.008%
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      Filtration performance was maintained
      • Xiang Y
      • Song Q
      • Gu W
      Decontamination of surgical face masks and N95 respirators by dry heat pasteurization for one hour at 70°C.
      ,
      • Celina MC
      • Martinez E
      • Omana MA
      • et al.
      Extended use of face masks during the COVID-19 pandemic - thermal conditioning and spray-on surface disinfection.
      -
      Microwave
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      2 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.


      4 min
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.
      Reduction of microbial load for some models
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      Varied damage:

      - Melting of the filtering material, internal foam sealing liner and elastic strips
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      Filtration degraded by 1.77%
      • Viscusi D
      • King W
      • Shaffer R
      Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models.


      Filtration was maintained in models where there was no melting
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.
      -
      Microwave-generated steam
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      ,
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      ,
      • Fisher E
      • Williams J
      • Shaffer R
      The effect of soil accumulation on multiple decontamination processing of N95 filtering facepiece respirator coupons using physical methods.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.
      ,
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.


      40 s
      • Fisher E
      • Williams J
      • Shaffer R
      The effect of soil accumulation on multiple decontamination processing of N95 filtering facepiece respirator coupons using physical methods.


      60 s
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      90 s
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      2 min
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.
      ,
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      ,
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      ,
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      3 min
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      Reduction of microbial load for some models;
      • Lore MB
      • Heimbuch BK
      • Brown TL
      • Wander JD
      • Hinrichs SH
      Effectiveness of three decontamination treatments against influenza virus applied to filtering facepiece respirators.
      ,
      • Fisher EM
      • Williams JL
      • Shaffer RE
      Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators.
      H1N1 virus detected after decontamination;
      • Heimbuch BK
      • Wallace WH
      • Kinney K
      • et al.
      A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets.


      The decontamination process was not affected by dirty
      • Fisher E
      • Williams J
      • Shaffer R
      The effect of soil accumulation on multiple decontamination processing of N95 filtering facepiece respirator coupons using physical methods.


      Reduction on microbial load (> 6 log10 reductions on S. aureus
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      Reduction on microbial load 6 log10 reduction on plaque forming unit of MS2 phage
      • Zulauf KE
      • Green AB
      • Ba ANN
      • et al.
      Microwave-generated steam decontamination of N95 respirators utilizing universally accessible materials.
      Varied damage:

      - The nose clip arced, with loss of adhesion between the nose clip and respirator
      • Pascoe MJ
      • Robertson A
      • Crayford A
      • et al.
      Dry heat and microwave-generated steam protocols for the rapid decontamination of respiratory personal protective equipment in response to COVID-19-related shortages.


      - A slight separation of the nose seal comfort pad5

      - Melting of the filtering material, internal foam sealing lining and elastic strips
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.


      - Sparks in the microwave
      • Bergman M
      • Viscusi D
      • Heimbuch B
      • Wander J
      • Sambol A
      • Shaffer R
      Evaluation of multiple (3-Cycle) decontamination processing for filtering facepiece respirators.
      ,
      • Viscusi DJ
      • Bergman MS
      • Eimer BC
      • Shaffer RE
      Evaluation of five decontamination methods for filtering facepiece respirators.


      Absence of damage
      • Viscusi DJ
      • Bergman MS
      • Novak DA
      • et al.
      Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease.
      ,