While disposable filtering facepiece respirators (FFRs), like N95s, are not approved for routine decontamination as conventional standards of care, FFR decontamination and reuse may be needed during times of shortage to ensure continued availability. Based on the limited research available, as of April 2020, ultraviolet germicidal irradiation, vaporous hydrogen peroxide, and moist heat have shown the most promise as potential methods to decontaminate FFRs. This webpage summarizes research about decontamination of FFRs before reuse. Whether and how a facility decides to implement specific crisis strategies is at the discretion of its administrators and should be based on present and projected risk mitigation needs and local, regional, and national availability of N95s. 

Before using any decontamination method, it should be evaluated for its ability to retain 1) filtration performance, 2) fit characteristics achieved prior to decontamination, and 3) safety of the FFR for the wearer (e.g. by inactivating SARS-CoV2).

Introduction

Reusing disposable filtering facepiece respirators (FFRs) has been suggested as a crisis capacity strategy to conserve available supplies for healthcare environments during a pandemic. Strategies for FFR extended use and reuse (without decontamination of the respirator) are currently available from CDC’s National Institute for Occupational Safety and Health (NIOSH).

The surfaces of an FFR may become contaminated while filtering the inhalation air of the wearer during exposures to pathogen-laden aerosols. The pathogens on the filter materials of the FFR may be transferred to the wearer upon contact with the FFR during activities such as:

• Adjusting the FFR
• Doffing the FFR improperly
• Performing a user-seal check when redoffing a previously worn FFR

A study evaluating the persistence of SARS-CoV-2 (the virus that causes COVID-19) on plastic, stainless steel, and carboard surfaces showed that the virus is able to survive for up to 72 hours [1]. One strategy to mitigate the contact transfer of pathogens from the FFR to the wearer during reuse is to issue five respirators to each healthcare worker who may care for patients with suspected or confirmed COVID-19. The healthcare worker will wear one respirator each day and store it in a breathable paper bag at the end of each shift. The order of FFR use should be repeated with a minimum of five days between each FFR use. This will result in each worker requiring a minimum of five FFRs, providing that they put on, take off, care for them, and store them properly each day. Healthcare workers should treat the FFRs as though they are still contaminated and follow the precautions outlined in our reuse recommendations. If supplies are even more constrained and five respirators are not available for each worker who needs them, FFR decontamination may be necessary.

Decontamination and subsequent reuse of FFRs should only be practiced where FFR shortages exist. At present, FFRs are considered one time use products and there are no manufacturer authorized methods for FFR decontamination before reuse. On March 29, 2020, the U.S. Food and Drug Administration (FDA) issued the first Emergency Use Authorization (EUA) for a decontamination process, and additional subsequent EUAs have been issued. The FDA Emergency Use Authorizations websiteexternal icon should be checked for the most up-to-date information. Only respirator manufacturers can reliably provide guidance on how to decontaminate their specific models of FFRs. In the absence of manufacturer’s recommendations, third parties may also provide guidance or procedures on how to decontaminate respirators without impacting respirator performance. Decontamination might cause poorer fit, filtration efficiency, and breathability of disposable FFRs as a result of changes to the filtering material, straps, nose bridge material, or strap attachments of the FFR. While decontamination and reuse of FFRs are not consistent with approved usage, this option may need to be considered when FFR shortages exist.

An effective FFR decontamination method should reduce the pathogen burden, maintain the function of the FFR, and present no residual chemical hazard. The filter media in NIOSH-approved respirators varies by manufacturer. The ability of the respirator filter media to withstand cleaning and disinfection are not NIOSH performance requirements. The NIOSH’s National Personal Protective Technology Laboratory (NPPTL) and other researchers have investigated the impact of various decontamination methods on filtration efficiency, facepiece fit of FFRs, and the ability to reduce viable virus or bacteria on the FFRs. This research is summarized below.

Crisis Standards of Care Decontamination Recommendations

Ultraviolet germicidal irradiation (UVGI), vaporous hydrogen peroxide (VHP), and moist heat showed the most promise as potential methods to decontaminate FFRs. Therefore, researchers, decontamination companies, healthcare systems, or individual hospitals should focus current efforts on these technologies. Specifically, the effectiveness of using these methods should be explored further with specific FFR models based on the manufacturers’ support to better understand the impact on the respirator performance, including filtration and fit. The respirator manufacturer should be consulted about the impact of the method on their respirators before considering the use of any method.

Information from the manufacturer or a third-party may be available, showing that respirators can be successfully decontaminated without impacting respirator performance. When this information is available, FFRs decontaminated in accordance with those recommendations can be worn for any patient care activities.

In the absence of guidance, or when information is available that a respirator cannot be decontaminated without negatively impacting the performance, respirators may still be decontaminated. However, given the uncertainties about the impact of decontamination on respirator performance, these FFRs should not be worn by healthcare providers (HCPs) when performing or present for an aerosol-generating procedure.

No current data exist to support the effectiveness of these decontamination methods specifically against SARS-CoV-2 on an FFR. Other pathogens may also be present on FFRs and limited data only exist  for other pathogens. Further work is needed to ensure SARS-CoV-2 and other pathogens are inactivated. Therefore, even after decontamination, these FFRs should be handled carefully.

HCPs should take the following precautionary measures before using a decontaminated FFR:

• Clean hands with soap and water or an alcohol-based hand sanitizer with at least 60% alcohol before and after touching or adjusting the FFR.
• Avoid touching the inside of the FFR.
• Use a pair of clean (non-sterile) gloves when donning the FFR and performing a user seal check.
• Visually inspect the FFR to determine if its integrity has been compromised.
• Check that FFR components such as the straps, nose bridge, and nose foam material did not degrade, which can affect the quality of the fit, and seal.
• If the integrity of any part of the FFR is compromised, or if a successful user seal check cannot be performed, discard the FFR and try another FFR.
• Users should perform a user seal check immediately after they don each FFR and should not use an FFR on which they cannot perform a successful user seal check.

Table 1 provides a summary of the crisis standards of care decontamination recommendations.

Table 1. Summary of crisis standards of care decontamination recommendations

Table 2 provides a summary of the decontamination methods evaluated in the referenced literature and the reported effect of each method on FFR performance.

Table 2. Summary of the decontamination method and effect on FFR performance

Table 3 provides a summary of the decontamination methods used, the treatment levels assessed, the microbes tested, and the antimicrobial efficacy as reported in the literature.

Table 3. Summary of decontamination method antimicrobial efficacy

Vaporous hydrogen peroxide, ultraviolet germicidal irradiation, and moist heat are the most promising FFR decontamination methods

Vaporous hydrogen peroxide, ultraviolet germicidal irradiation, and moist heat are the most promising decontamination methods. If FFR decontamination is considered, these methods do not appear to break down filtration or compromise the FFR; however, many of these methods can only be used for limited times.

Vaporous hydrogen peroxide (VHP)

Investigations into VHP decontamination of FFRs provide evidence of minimal effect to filtration and fit while demonstrating 99.9999% efficiency in killing bacterial spores. VHP did not reduce the filtration performance of ten N95 FFR models tested while showing a 6-log reduction in Geobacillus stearothermophilus spores [2-4].

In a report prepared by Battelle Memorial Institute, the 3M 1860 FFR was shown to maintain filtration performance for 50 treatment cycles of VHP, also referred to as HPV by some decontamination system manufacturers, using the Clarus^® R HPV generator form Bioquell (utilizing 30% H₂O₂). Additionally, FFR fit was shown to be unaffected for up to 20 VHP treatments cycles using NPPTL’s Static Advanced Headform [4, 5]. Strap degradation occurred after 20 treatment cycles. Kenney et al. co-contaminated 3M 1870 FFRs with three bacteriophages, T1, T7, and Phi 6, and decontaminated the FFRs using VHP generated from the Bioquell’s BQ-50 system. The VHP treatment was shown to inactivate >99.999% of all phages which was below the limit of detection [6].

Viscusi et al. found that 9 FFR models (three particulate N95, three surgical N95 FFRs and three P100) exposed to one cycle of VHP treatment using the STERRAD 100S H₂O₂ Gas Plasma Sterilizer (Advanced Sterilization Products, Irvine, CA) had filter aerosol penetration and filter airflow resistance levels similar to untreated models; however, Bergman et al. found that three cycles of VHP treatment using the STERRAD 100S H₂O₂ Gas Plasma Sterilizer negatively affected filtration performance [2, 3].

Bergman et al. measured acceptable filtration performance for six FFR models (three particulate and three surgical FFRs) that received three cycles of VHP treatment using the Clarus^® R HPV generator (utilizing 30% H₂O₂) [3]. VHP is a promising method with a potential for high capacity throughput, but certain VHP systems, such as the Clarus^® R HPV generator, may be more suitable for FFR decontamination.

Ultraviolet germicidal irradiation (UVGI)

UVGI is a promising method but the disinfection efficacy is dependent on dose. Not all UV lamps provide the same intensity thus treatment times would have to be adjusted accordingly. Moreover, UVGI is unlikely to kill all the viruses and bacteria on an FFR due to shadow effects produced by the multiple layers of the FFR’s construction.

Acceptable filtration performance was recorded for eleven FFR models exposed to various UV doses ranging from roughly 0.5–950 J/cm² and UVGI was shown to have minimal effect on fit [2, 3, 7, 8, 9, 10]. Heimbuch et al. tested filtration and fit of 15 FFRs and found no adverse effects to FFR performance [11]. Lindsley et al. reported a reduction of the durability of materials of the FFRs for doses ranging from 120–950 J/cm²; however, an approximate inactivation of 99.9% of bacteriophage MS2, a non-enveloped virus, and H1N1 influenza A/PR/8/34 were achieved with much lower doses of approximately 1 J/cm² [12–14]. Heimbuch et al. tested the performance of 1 J/cm² of UVGI against Influenza A (H1N1), Avian influenza A virus (H5N1), Influenza A (H7N9) A/Anhui/1/2013, Influenza A (H7N9) A/Shanghai/1/2013, MERS-CoV, and SARS-CoV and reported virus inactivation from 99.9% to greater than 99.999% [11].

UVGI is harmful. Proper precautions are required to avoid UVGI exposure to skin or the eyes.

Moist heat

Moist heat, consisting of 60°C and 80% relative humidity (RH) caused minimal degradation in the filtration and fit performance of the tested FFRs [3, 9, 10]. Heimbuch et al. disinfected FFRs contaminated with H1N1 influenza using moist heat, of 65°C and 85% RH, and achieved a minimum of 99.99% reduction in virus [14].

One limitation of the moist heat method is the uncertainty of the disinfection efficacy for various pathogens.

Steam treatment and liquid hydrogen peroxide are promising methods with some limitations

Steam treatment

Steam treatment may be a suitable approach for decontaminating FFRs. The limited number of studies for steam report minimal effect on FFR filtration and fit performance and a minimum of 99.9% reduction in H1N1 influenza and bacteriophage MS2 [14, 15].

Fisher et al. used microwave steam bags, designed for disinfecting infant feeding equipment, to decontaminate six FFR models and achieved 99.9% inactivation of MS2 bacteriophage. Filtration performance of all tested FFRs scored above NIOSH certification requirements. Three FFRs were further evaluated for three cycles of steam exposure and demonstrated no change in filtration performance [15]. Bergman et al. also demonstrated acceptable filtration performance after three cycles of exposure to microwave generated steam [3]. Microwave generated steam had little effect on FFR fit after exposure to up to three cycles of steam [9, 10].

Using microwaves to produce steam to decontaminate FFRs is not without limitations. Not all microwaves are constructed the same and some are more powerful than others. The effect of higher power microwaves on FFRs is unknown. Furthermore, the metal nosebands of FFRs may cause arcing, sparks inside the microwave oven, during exposure to microwaves.

Liquid hydrogen peroxide

Liquid hydrogen peroxide showed no effect on FFR filtration performance [3, 7]. Bergman et al. evaluated six FFRs for filtration performance after a 30-minute submersion in 6% hydrogen peroxide. All six FFR models tested demonstrated no changes in filter performance after three cycles of decontamination. FFR fit and disinfection efficacy were not assessed for this method.

Table 4 provides a summary of the decontamination methods evaluated for each FFR model. This table does not serve to confirm that the decontamination method was effective for each FFR model. This table serves to alert the reader about the availability of more information about the decontamination methods for specific FFR models in the literature.

Table 4. Decontamination methods evaluated for each FFR model

Decontamination methods that changed FFR performance or function

Based on the NIOSH-evaluated research, employers should not use the following methods unless data on the safety and effectiveness of such methods become available.

Autoclave, dry heat, isopropyl alcohol, soap, and dry microwave irradiation

Decontamination using an autoclave, 160°C dry heat, 70% isopropyl alcohol, microwave irradiation and soap and water caused substantial filter degradation to both FFRs and particle penetration levels did not meet the levels that NIOSH would allow for approval[2, 7].

Bleach

Viscusi et al. measured the filtration performance of two FFR models submerged into bleach (0.525% sodium hypochlorite and 5.25% sodium hypochlorite) and noted some degradation in filtration performance but not below acceptable levels [7].  Viscusi et al. and Bergman et al. also examined the performance multiple FFR models submerged ino.6 % sodium hypochlorite and found filtration performance was not affected; however, residual bleach odors and chlorine off-gassing were noted [2, 3]. Viscusi et al. concluded that bleach decontamination of FFRs should be further evaluated using lower bleach concentration and chemical methods for neutralizing residuals [2].

Disinfectant wipes

Heimbuch et al. evaluated biological decontamination efficacy and filtration penetration following aerosol exposure of mucin or viable Staphylococcus aureus [18]. Following aerosol exposure, respirators were cleaned with three types of wipes: hypochlorite, benzalkonium chloride (BAC), or nonantimicrobial. Particle penetration following cleaning yielded mean values <5%. The highest penetrations were observed in FFRs cleaned with BAC wipes. The BAC wipe caused one sample of FFRs to exceed 5% penetration. Filter penetration following various decontamination methods was shown in this study to vary based on the decontamination method and the model of FFR.

Ethylene oxide (EtO) is promising, but may be harmful to the wearer

EtO is not recommended as a decontamination method as it may be harmful to the wearer.

EtO was shown to not harm filtration performance for the nine tested FFR models [2, 3, 7]. All tests were conducted for one hour at 55˚C with EtO gas concentrations ranging from 725 to 833 g/L. Six models that were exposed to three cycles of 736 mg/L EtO all passed the filtration performance assessment [3].

Possible effects of EtO treatment on FFR fit were not studied. However, EtO treatment does not cause visible physical changes to the appearance of FFRs [2, 3].

A concern about using EtO for decontamination of large numbers of FFRs is throughput, since relatively long aeration cycles are needed to ensure removal of the highly toxic EtO gas [2]. Any use of EtO should be accompanied by studies to ensure no off-gassing into the breathing zone of the wearer as EtO is carcinogenic and teratogenic. Chronic inhalation of EtO has been linked to neurologic dysfunction and may cause other harmful effects to the wearer [16]. EtO should be used in accordance with Occupational Safety and Health Administration standard 29 CFR 1910.1047 [17].

Other methods for consideration which have not been tested

Hospitals may possess other decontamination capabilities that may be feasible. For example, photodynamic inactivation of pathogens using methylene blue plus visible light exposure is used to treat blood products; that method has been suggested to decontaminate PPE. There are currently no data to evaluate the effect of this method on FFR filtration and fit [19].

References

1. van Doremalen, N., et al., Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1. J New England Journal of Medicine, 2020.
2. Viscusi, D.J., et al., Evaluation of five decontamination methods for filtering facepiece respirators. Annals of occupational hygiene, 2009. 53(8): p. 815-827.
3. Bergman, M., et al., Evaluation of Multiple (3-Cycle) Decontamination Processing for Filtering Facepiece Respirators. Journal of Engineered Fibers and Fabrics, 2010. 5(4): p. 33-41.
4. Battelle. Final Report for the Bioquell Hydrogen Peroxide Vapor (HPV) Decontamination for Reuse of N95 Respirators. 2016; Available from: https://www.fda.gov/emergency-preparedness-and-response/mcm-regulatory-science/investigating-decontamination-and-reuse-respirators-public-health-emergenciesexternal icon.
5. Bergman, M.S., et al., Development of an advanced respirator fit-test headform. Journal of Occupational and Environmental Hygiene, 2014. 11(2): p. 117-125.
6. Kenney, Patrick, et al. Hydrogen Peroxide Vapor sterilization of N95 respirators for reuse. medRxiv (2020).
7. Viscusi, D.J., King, W.P., Shaffer, R.E., Effect of decontamination on the filtration efficiency of two filtering facepiece respirator models. Journal of the International Society for Respiratory Protection, 2007. 24: p. 93-107.
8. Lindsley, W.G., et al., Effects of ultraviolet germicidal irradiation (UVGI) on N95 respirator filtration performance and structural integrity. Journal of Occupational and Environmental Hygiene 2015. 12(8): p. 509-517.
9. Bergman, M., et al., Impact of Three Cycles of Decontamination Treatments on Filtering Facepiece Respirator Fit. Journal of the International Society for Respiratory Protection, 2011. 28(1): p. 48-59.
10. Viscusi, D.J., et al., Impact of three biological decontamination methods on filtering facepiece respirator fit, odor, comfort, and donning ease. Journal of Occupational and Environmental Hygiene, 2011. 8(7): p. 426-36.
11. Heimbuch, B.K. and D. Harnish. Research to Mitigate a Shortage of Respiratory Protection Devices During Public Health Emergencies. 2019; Available from: https://www.ara.com/news/ara-research-mitigate-shortage-respiratory-protection-devices-during-public-health-emergenciesexternal icon
12. Fisher, E.M. and R.E. Shaffer, A method to determine the available UV‐C dose for the decontamination of filtering facepiece respirators. Journal of Applied Microbiology, 2011. 110(1): p. 287-295.
13. Mills, D., et al., Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators. American Journal of Infection Control, 2018. 46(7): p. e49-e55.
14. Heimbuch, B.K., et al., A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets. American Journal of Infection Control, 2011. 39(1): p. e1-e9.
15. Fisher, E.M., J.L. Williams, and R.E. Shaffer, Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators. PLoS One, 2011. 6(4).
16. Rutala, W.A. and D.J. Weber. Guideline for disinfection and sterilization in healthcare facilities, 2008. 2008; Available from: https://www.cdc.gov/infectioncontrol/guidelines/disinfection/.
17. Occupational Safety and Health Administration. Ethylene oxide: 29 CFR 1910.1047
18. Heimbuch, B.K., et al., Cleaning of filtering facepiece respirators contaminated with mucin and Staphylococcus aureus. American Journal of Infection Control, 2014. 42(3): p. 265-270.
19. Eickmann, M., et al., Inactivation of Ebola virus and Middle East respiratory syndrome coronavirus in platelet concentrates and plasma by ultraviolet C light and methylene blue plus visible light, respectively. Transfusion, 2018. 58(9): p. 2202-2207.
20. 3M. Disinfection of Filtering Facepiece Respirators. Technical Bulletin 2020; Available from: https://multimedia.3m.com/mws/media/1824869O/decontamination-methods-for-3m-n95-respirators-technical-bulletin.pdfpdf iconexternal icon.

Other resources

• Lowe, J.J. N95 Filtering Facemask Respirator Ultraviolet Germicidal Irradiation (UVGI) Process for Decontamination and Reusepdf iconexternal icon. 2020.
• N95DECON [2020]. A scientific consortium for data-driven study of N95 filtering facepiece respirator decontaminationexternal icon.
• NIST. Tool for Evaluation of Vaporized Hydrogen Peroxide Disinfection of N95 Masks in Small Roomsexternal icon.