What is the evidence around reuse of face filtering respirators (FFRs), including N95 respirators?  

Posted on April 15, 2020 by Kristin Walters

Summary

Supply chain restrictions to appropriate PPE protection of healthcare workers remains an issue in Canada and internationally prompting the question of re-using face filtering respirators (FFR’s).  At the time of this review, there are no manufacturer-supported recommendations for sterilization of FFRs between use.  Should access to PPE become more constrained, a number of other entities have provided evidence supporting various techniques of FFR decontamination which may be used in order to protect healthcare workers and front line staff as supported by Health Canada (3) and the CDC/NIOSH (14). 

I.   CURRENT STATUS OF N95 REUSE

  • A study evaluating the persistence of SARS-CoV-2 on plastic, stainless steel, and cardboard surfaces showed that the virus is able to survive for up to 72 hours (1).
  • N95 respirators are considered single use and there are no manufacturer authorized methods for decontamination prior to use at this time.
  • On April 7, 2020, Health Canada issued regulatory considerations for the reprocessing of N95 respirators citing the CDC’s recommendation to encourage ultraviolet germicidal irradiation (UVGI), vaporous hydrogen peroxide (VHP), and moist heat as the preferred methods to decontaminate face filtering respirators (FFRs) (3).
  • The CDC suggests that the number of reuses should be limited to no more than 5 uses per FFR device (14).
  • Caution in decontaminating N95s should be exercised as unsuitable methods of decontamination include soapy water, alcohol, bleach immersion, and overnight storage (4).
  • The CDC and NIOSH do not recommend that FFRs be decontaminated as this is inconsistent with their intended use, however there is recognition that this may need to be considered as shortages arise.
  • The CDC/NIOSH have released recommended guidance for extended use of N95 respirators which suggests that respirators can function for 8 continuous hours effectively (14).

II.   HEAT AND HUMIDITY USED FOR DECONTAMINATION OF N95 MASKS

  • Heat and humidity measures (85°C, 60-85% humidity) have been tested on 3M 1860 and 3M 8210 Plus N95 models where after five cycles of heating, both respirators pass quantitative fit testing and did not show degradation of mask filtration efficiency. This method is scalable from 1-1,000 masks using a single industrial convection oven (5).
  • Related coronaviruses have been shown to be inactivated at 60 -75°C at 80% humidity for 30 minutes, however this has not yet been a proven method against COVID-19 specifically. Devices that can operate at 65-80°C, 50-85% humidity includes warming cabinets, water baths, autoclaves, and ovens (4).
    • Filter performance was shown to withstand 5 cycles of decontamination

Fit was shown to be maintained after 1 cycle.

III.   VAPOROUS HYDROGEN PEROXIDE (VHP) DECONTAMINATION

  • A protocol developed by Duke University recommends VHP (480ppm) applied over a 45-minute cycle to N95 respirators (10).
  • An FDA study revealed that N95 respirators could withstand up to 30 cycles of VHP decontamination before the elastic straps began to degrade (11).
  • One study employed the use of VHP of an operating room by sealing off heating, ventilation, and air conditioning (HVAC)using polyethylene sheeting and tape.  The instrument employed in this study included a Bioquell Clarus C hydrogen peroxide vapor generator using 30% w/w H2O2 solution with cycle parameters of H2O2 injection and dwell rate of 8.0 g/min (6)
  • As of March 28, 2020, the FDA issued an Emergency Use Authorization (EUA) permitting the use of the Battelle Decontamination system compatible with N95 respirators (2). This system requires approximately 180 minutes of processing and 300 minutes of aeration and is not compatible with cellulose-based material.  
  • Saskatchewan Health Authority partnered with a private industry (VIDO-InterVac) to develop a protocol for using VHP decontamination and reuse of N95 respirators.  It was found that each N95 respirator could undergo 5-10 cycles of decontamination while maintaining effectiveness and fit (13).
  • Outstanding questions remain regarding the safety of reuse and potential for inhalation of residual disinfectant (12).

IV.   ULTRAVIOLET GERMICIDAL IRRADIATION (UVGI) DECONTAMINATION

  • A procedure for surface decontamination of N95 respirators has been established using UVGI
  • The optimal wavelength required to inactivate coronavirus is approximately 260nm (range 200-320nm), and for SARS coronaviruses the range is 22-304nm). The dose required to disable 90% of coronaviruses in water is 2.1 mJ/cm2  (6)
  • Another study found that UV-C irradiation at a dose of ≥ 1 J/cm2 at 254 nm peak wavelength inactivates SARS-CoV-2 analogues (≥3-log) on the majority of N95 respirators (4).
  • Risks presented with UVGI decontamination include variable dose to all layers of the mask and the straps remaining as a source of residual contamination (4).

V.   DECONTAMINATION METHODS PROVEN POTENTIALLY INEFFECTIVE

  • As a source of conflicting information to the available recommendations and literature, the CDC suggests decontamination using an autoclave, 160°C dry heat, 70% isopropyl alcohol, microwave irradiation and soap and water caused significant filter degradation to FFRs and particle penetration levels did not meet levels for NIOSH approval (7, 8).
  • Although Ethylene Oxide has been shown to have promising results in terms of decontamination without affecting filtration performance, it has not been recommended by the CDC as it may have harmful effects on the wearer (9).

VI.   ADDITIONAL RESOURCES AND PROTOCOL FOR REUSE OF FFRs

Questions? Comments? Does this need to be updated? Do you have valuable points to add ? Please email ask.reakt@ubc.ca.

References

  1. Van Doremalen, N., et al., Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV. J New England Journal of Medicine. March 17, 2020. [Online] https://www.nejm.org/doi/full/10.1056/NEJMc2004973

 Accessed: April 14, 2020

  1.     FDA Batelle Memorial Institute Emergency Use Authorization. March 29, 2020. [Online] https://www.fda.gov/media/136529/download.

Accessed: April 14, 2020

  1.     Health Canada. Health Products and Food Branch, Medical Devices Directorate. April 7, 2020. [Online] https://www.healthcarecan.ca/wp content/uploads/HealthCanada/NoticeReprocessingN95Respirators.pdf?utm_source=Master+List&utm_campaign=fab2ca41f3-EMAIL_CAMPAIGN_2019_03_07_07_25_COPY_01&utm_medium=email&utm_term=0_0bdb7418ff-fab2ca41f3-1266822145

Accessed: April 14, 2020

  1.     N95 Decon. Caution When Reusing N95 Respirators. [Online] s://www.n95decon.org/publications

Accessed: April 14, 2020

  1.     Loïc Anderegg, C., et al., A Scalable Method of Applying Heat and Humidity for Decontamination of N95 Respirators During the COVID-19 Crisis. MedRxiv Preprint. April 14, 2020 [Online] https://www.medrxiv.org/content/10.1101/2020.04.09.20059758v1

Accessed: April 14, 2020

  1.     Perkins, D.J., et al., COVID-19 Global Pandemic Planning: Decontamination and Reuse Process for N95 Respirators. MedRxiv Preprint. April 14, 2020. [Online] https://www.medrxiv.org/content/10.1101/2020.04.09.20060129v1

Accessed: April 14, 2020

  1.     Viscusi, D.J., et al., Evaluation of five decontamination methods for filtering facepiece respirators. Annals of occupational hygiene, 2009. 53(8): p. 815-827.
  2.     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.
  3. CDC. Decontamination and Reuse of Filtering Facepiece Respirators. April 9, 2020. [Online] https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html

Accessed: April 14, 2020

  1. Schwarz, A., et al., Decontamination and Reuse of N95 Respirators with Hydrogen Peroxide Vapor to Address Worldwide PPE Shortages During the SARS-CoV-2 (COVID-19) Pandemic. Duke University & Health System.  [Online] https://www.safety.duke.edu/sites/www.safety.duke.edu/files/N95%20Decontamination%20Procedure.pdf

Accessed: April 14, 2020

  1. FDA. Final Report for the Bioquell Hydrogen Peroxide Vapor (HPV) Decontamination for Reuse of N95 Respirators. Study Number 3245. July 22, 2016. [Online] https://www.fda.gov/media/136386/download

Accessed: April 14, 2020

  1. Public Health Ontario. Covid-19 – What We Know So Far About…Reuse of Personal Protective Equipment. April 4, 2020. [Online] https://www.publichealthontario.ca/-/media/documents/ncov/covid-wwksf/what-we-know-reuse-of-personal-protective-equipment.pdf?la=fr

Accessed: April 14, 2020

  1. Saskatchewan StarPhoenix. SHA and VIDO-InterVac Partner to Decontaminate and Reuse N95 Masks. April 11, 2020. [Online] https://thestarphoenix.com/news/local-news/sha-and-vido-intervac-partner-to-decontaminate-and-reuse-n95-masks/

Accessed: April 14, 2020

  1. CDC/NIOSH. Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare. March 27, 2020. [Online] https://www.cdc.gov/niosh/topics/hcwcontrols/recommendedguidanceextuse.html#respreuse

Accessed: April 14, 2020

Disclaimer

The above is intended to serve as a rapidly-created, accessible source of information curated by medical students and healthcare professionals. It is for educational purposes only and is not a complete reference resource. It is not professional medical advice, and is not a substitute for the discretion, judgment, and duties of healthcare professionals. You are solely responsible for evaluating the information above.