April 21, 2020

N95 Mask Decontamination and Reuse

Introduction: N95 filtering facepiece respirators (FFP, from here out referred to as N95) are designed to filter out 95% of airborne particles and are intended for single use. During the COVID19 pandemic, N95s are in short supply forcing us to consider reuse of the devices in order to maintain protection in clinical environments. However, there is only limited data on safe decontamination and reuse practices. As of the writing of this post, it is unclear when adequate supplies of N95s will be available and numerous hospitals have already started reuse protocols. Here, we review the current literature and recommendations. It’s important to recognize that both ability to filter and fit of the N95 are important in terms of use and reuse. Of note, residual virus may be present after any of these methods but, amounts remaining should not produce clinical infection.

Method #1: 70 – 75% Ethanol Bath Followed by Drying

  • Decontamination: Ethanol has been found to be effective in viral decontamination after as little as 10 minutes of exposure (Fischer 2020)
  • Integrity: Filtration efficacy fell below 95% after a single decon cycle (56%) (Stanford Medicine 2020)
  • Recommendation: Ethanol Bath is not a safe method for decon as it results in non-protective masks after a single decon cycle.

Method #2: Dry Heat – 70oC

  • Decontamination: 60 minutes of heating at 70oC (158oF) is effective in viral decontamination of the N95 mask but may leave residual virus on metal portions (ie nasal bridge piece) (Fischer 2020)
  • Integrity: Adequate mask integrity was preserved for up to two decon cycles (Fischer 2020)
  • Recommendation: Convection heating (not your typical home oven as temperatures in these cannot be maintained minute to minute) at 70oC is effective and yields a usable mask. This approach should not be performed more than twice on any given mask.

Method #3: Autoclave

  • Decontamination: 15 minutes at 121oC (total cycle time of 40 minutes) was effective in decontamination (Kumar 2020)
  • Integrity: All 3M masks tested in the Kumar study maintained integrity after a single decon cycle but, fit was lost in one of the most common models (3M 1860) by 3 cycles
  • Recommendation: Autoclave can be safely used for a single decon cycle but the ability to use it for multiple decon cycles will depend on the mask in question

Method #4: Time

  • Background: Though data is limited, available evidence shows that SARS-CoV-2 can persist on inanimate surfaces for up to 72 hours. The infectiveness of virus on these surfaces at any time interval is unknown.
  • Idea: Cycle through masks where each mask gets at least 72 hours of non-use after a day of use
  • Protocol
    • Start on day#1 with 4 N95 masks
    • Use mask #1 on day #1. After use, store in a dry atmosphere for 3-4 days
    • Reuse after at least 72 hours
  • Note: I (Anand Swaminathan) have been using this approach since the beginning of the pandemic. I have used each mask for a total of 4 times (3 decon cycles)
  • Attribution: Thanks to Dr. Jessica Lopez who chatted with N95 technology inventor Dr. Peter Tsai about this approach

Method #5: UV Light (260-285 nm)

  • Decontamination: 60 minutes of exposure effectively decontaminated the mask though the metal portions only required 10 minutes (Fischer 2020). Prior work showed safety with only 30 minutes of exposure (Stanford 2020)
  • Integrity: Adequate mask integrity was preserved for up to three decon cycles (Fischer 2020)
  • Recommendation: Nebraska Medicine has an extensive explanation of the protocol for doing UV decon. If you have the correct setup, N95s can be used up to 4 times with 3 decon cycles

Method #6: Vaporized H2O2 (VHP)

  • Decontamination: 10 minutes of VHP effectively decontaminated both mask and metal (Fischer 2020).
  • Integrity: Adequate mask integrity was preserved for at least three decon cycles (Fischer 2020) and possibly up to ten cycles (Kumar 2020)
  • Recommendation: VHP appears to be the best method as it can be rapidly performed and may yield the most uses.
Decontamination of SARS-CoV-2 By 4 Different Methods (Fischer 2020)

Decontamination of SARS-CoV-2 By 4 Different Methods (Fischer 2020)

Decontamination of N95 Masks (Stanford 2020)

Conclusion: Based on the best current evidence, vaporized H2O2 appears to be the best method for N95 decontamination followed by UV light. For those without access to these technologies, the approach of allowing the mask to “air out” for 72 hours is reasonable.

References

  1. Fischer RJ et al. Assessment of N95 respiratory decontamination and re-use for SARS-CoV-2. Preprint without peer review 04.15.20. [Link is HERE]
  2. Kumar A et al. N95 mask decontamination using standard hospital sterilization technologies. Preprint without peer review 04.08.20. [Link is HERE]
  3. van Doremalen N et al. Aerosol and surface stability of SARS-CoV-2 as Compared with SARS-CoV-1. NEJM 4.16.20. [Link is HERE]
  4. Stanford Medicine: Addressing COVID-19 Face Mask Shortages
  5. Nebraska Medicine: N95 Filtering Facepiece Respirator Ultraviolet Germicidal Irradiation (UVGI) Process for Decontamination and Reuse

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)

Cite this article as: Anand Swaminathan, "N95 Mask Decontamination and Reuse", REBEL EM blog, April 21, 2020. Available at: https://rebelem.com/n95-mask-decontamination-and-reuse/.
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Anand Swaminathan

Clinical Assistant Professor of Emergency Medicine at St. Joe's Regional Medical Center (Paterson, NJ)
REBEL EM Associate Editor and Author
17 Comments
  • Satadru Pramanik
    Posted at 11:05h, 21 April Reply

    As per “Stanford 2020” steaming for 10 minutes seemed to be quite effective for decontamination (as mentioned in the above graphic). This would be similar to autoclave, but maybe less harmful to fit, since you’re not applying higher temperatures and pressures?

    I’ve love to see some work evaluating loss of fit after 10 minutes of simple steaming, since steamers are so easy to find.

    • Salim Rezaie
      Posted at 11:10h, 21 April Reply

      Hello Satadru,
      Agree it makes sense, but we just don’t have the evidence…Remember N95 masks were not created to be re-used. We have to balance staff safety with best available evidence. Currently there is limited evidence on re-use procedures. What we do have does not tell us much about autoclaves, so use at yours and your staffs risk is what I would say. Currently best evidence seems to be time and dry heat. As we get more evidence and studies, it may pan out that autoclaves are safe or safer. Hope that makes sense.

      Salim

  • rene osorio
    Posted at 18:00h, 21 April Reply

    jajajaja como si fuera a funcionar la “revulcanización” esta y despues de 40 hrs de uso el tamaño de los poros del material regrese a ser como el original despues de hacer eso… no ya en serio… por algo son desechables, se desinfectan pero no se garantiza que el sistema de barrera quede intacto y como nuevo, NO SON REUTILIZABLES… NI LAS JERINGAS VUELVEN A USAR LIMPIANDOLAS ASI!!!! 😖

  • rene osorio
    Posted at 18:03h, 21 April Reply

    jajajaja como si fuera a funcionar la revulcanización y despues de 40 hrs de uso el tamaño de los poros del material regrese a ser como el original despues de hacer eso… no ya en serio… por algo son desechables, se desinfectan pero no se garantiza que el sistema de barrera quede intacto y como nuevo, NO SON REUTILIZABLES… NI LAS JERINGAS VUELVEN A USAR LIMPIANDOLAS ASI!!!! 😖

  • rene osorio
    Posted at 18:06h, 21 April Reply

    jajajajaja que feo, escribí “n o s o n” y me lo traducen como “no hay hijo”… y yo creyendo q era mi error de escritura

    • Salim Rezaie
      Posted at 18:08h, 21 April Reply

      Apologies…able to write in English?

  • James Ndirangu
    Posted at 11:52h, 22 April Reply

    1. How about soapy water and rinse out followed by air drying…. thinking of developing countries here.
    2. Any word on reuse of surgical masks….. Again poor countries without N95

    • Salim Rezaie
      Posted at 11:58h, 22 April Reply

      Hello James,
      Personally I would skip the soapy water and rinse as it is unknown what this will do to the fit of the mask…I would simply use a time based method and cycle through 4 masks as outlined in the post. As for surgical masks, these were also not intended for reuse…It is less than optimal but I suspect it is better than nothing…I would most likely do a time based rotation of masks as well, but this is just my opinion. Unaware of studies looking at reuse of surgical masks. Hope this helps…TY for reading and stay safe.

      Salim

  • Nerine Schaper
    Posted at 12:24h, 22 April Reply

    What about chlorhexadine solution?

    • Salim Rezaie
      Posted at 12:41h, 22 April Reply

      It’s a great question and my honest answer is, I have not seen evidence of this working, but to be fair, I have not seen evidence against this working either. There appear to be far superior strategies that have a better evidence base currently than one we don’t have a strong one for.

      Salim

  • Ronit abdoo
    Posted at 13:56h, 23 April Reply

    Here’s an article that supports the evidence presented in this article https://tuttnauer.com/blog/hydrogen-peroxide-vapor-sterilization-respirator-face-masks-reuse

  • COVID-19: Prevention - REBEL EM - Emergency Medicine Blog
    Posted at 17:31h, 28 April Reply

    […] REBEL EM: N95 Mask Decontamination and Reuse […]

  • Parlong Mega
    Posted at 18:32h, 06 May Reply

    DTC3B N95is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles. The ‘N95’ designation means that when subjected to careful testing, the respirator blocks at least 95 percent of very small test paticles

  • Mitony
    Posted at 23:32h, 01 June Reply

    I remember in year 2017, I saw one nano fiber masks in an exhibition, Its very impressive, as it can be reused for almost one month. The company is called Suzhou Nice Sweater Clothes Co., Ltd. Their brand is called Nayi. I had one of their mask on their exhibition. Anyone got interest, please try google this company, I can not find their name card now.

  • emDOCs.net – Emergency Medicine EducationEM Mindset: COVID-19 Edition - Why we must lead - emDOCs.net - Emergency Medicine Education
    Posted at 02:21h, 11 June Reply

    […] it was needed most. Strategies for decontaminating N95 masks for reuse were shared on Twitter and blogs. Treatment algorithms for the management of hypoxemia including both noninvasive and invasive […]

  • David
    Posted at 10:43h, 04 July Reply

    Thank you for the in-depth guide! It’s very useful for those who are using an N95 mask for the first time

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