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Updated: November 25, 2020

How can N95 masks be safely reused?

Summary

The following is a brief summary of the best available evidence from trusted sources that provides high quality information on the current evidence regarding the re-use of N95 masks by health care providers in the context of COVID-19. Three systematic reviews, two evidence syntheses, one rapid review three national guidelines and one manufacturer’s guidance were used in the creation of this REAL note. For additional information about each of the sources, see the Table below.  For additional information about each of the sources, see the Table below.

To conserve the supply of N95 masks (respirators), a combination of strategies is recommended by organizations in Canada and the United States (US) including extended use and limited re-use. For example, the Canadian Agency for Drugs and Technologies in Health (CADTH) provides guidance on the extended use of N95 masks in: Optimization of N95 Respirator Masks During Supply Shortages [6]. Two US organizations, the Centers for Disease Control and Prevention (CDC) and the Stanford Medicine-Anesthesia Informatics and Media Lab, suggest that extended use can be up to eight hours per wearer but should cease after exposure to aerosol generating procedures, fluid contamination, or close contact with infectious patients [5,7]. In terms of re-using masks, in its Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare Settings, the CDC suggests that limited re-use should be based on manufacturer’s guidelines. If such guidance is unavailable, the CDC suggests that one strategy is to issue five respirators to each wearer such that they wear one each day and store it in a breathable bag by the end of their shift with a minimum of five days between each use [7]. It is advised that, with the re-use of respirators, users should re-use their own masks [7]CADTH suggests that layering covering N95 masks using face shields, surgical masks or other disposable coverings may prolong use by reducing surface contamination [6]. Health Canada provides guidance on Optimizing the use of masks and respirators during the COVID-19 outbreak including discarding masks that have visible signs of damage, do not have intact straps, or are unable to confirm a seal check [8]. One review of Medical Masks vs N95 Respirators for Preventing COVID-19 in Health Care Workers found that medical masks were sufficient for non-aerosolized procedures [2]
  
Several reviews found that UV radiation was the most tested method of reprocessing N95 masks. While most studies analyzed in these reviews were conducted in laboratory environments, many found that UV was able to significantly decrease viral load on masks without negatively impacting performance, fit, or function [1,4,6]. Two reviews found that microwave treatment and vaporized hydrogen peroxide (VHP) were also tested, with beneficial results [3,6]Health Canada has regulatory requirements that manufacturers of mask reprocessing devices must meet before authorization [8]. Currently, a few methods incorporating VHP and UV-C radiation have received authorization in Canada [9]. As started by the CDC, most promising reprocessing techniques are UV germicidal irradiation with UV-C light, vaporized hydrogen peroxide, moist heat or steam and dry heat [6]
 
A major manufacturer of N95 respirators, 3M, has released an evaluation of the impact that different reprocessing methods have on specific mask models although they recommend against reprocessing of any kind [10]. Based on 3M’s current findings, the microwave treatment method is not recommended, as it was shown to melt metal components essential for the proper fitting of masks [10]. However, several VHP methods passed filtration efficiency and fit-related evaluations, which have received authorization by the U.S. Food and Drug Administration (FDA) [10]

Evidence

What‘s Trending on Social Media and Media

Over 300,000 tweets including #GetMePPE have been posted since March 2020 as the global mask shortage grows and healthcare workers search for personal protective equipment online.

A Twitter review reflects many different recommendations regarding mask reuse protocols with varying qualities of evidence. 

Multiple YouTube videos surface averaging 150,000 views and instruct users on how to disinfect their own masks – accuracy of information is undetermined. 

The process of assigning one mask for each day of the week, bagging that mask and returning to the mask seven days later gains popularity in social media as masks and decontamination processes become less available.

Organizational Scan

The Federal Government of Canada announced an action plan on March 20th, 2020 to collaborate with businesses and manufacturers to retool their current operations in an attempt to produce medical equipment such as ventilators, masks, etc. [21].  
 
Multiple national and provincial health organizations have endorsed the extended use of facemasks by clinicians for multiple patient encounters [22] [23].  
 
Local innovations are taking place across Ontario to assist in providing health care workers adequate PPE supplies to address the current shortage [26] 
 
For example, Prescientx, an Ontario firm has built and started taking orders on a high-volume conveyor style N95 mask UV disinfector, which uses high-intensity UVC lamps and reflective aluminum tunnels to rapidly disinfect up to 500 masks an hour [24].  
 
In another example, innovators at the Sunnybrook Health Sciences Centre are developing a full-face snorkel mask which provides protection from the environment to the eyes, nose and mouth should the need arise [25].  

Review of Evidence

Resource Type/Source of Evidence Last Updated
Decontaminating N95 masks with Ultraviolet Germicidal Irradiation (UVGI) does not impair mask efficacy and safety: A Systematic Review
— O’Hearn et al.
Systematic Review

This review found that UV irradiation decreased viral loads of N95 FFRs without significantly impacting fit, certification standard, or airflow resistance.

Last Updated: July 17, 2019
Medical Masks vs N95 Respirators for Preventing COVID-19 in Health Care Workers A Systematic Review and Meta-Analysis of Randomized Trials
— Bartoszko et al.
Systematic Review

This review found that medical masks and N95 respirators provide similar protection against coronavirus in health care workers during non-aerosol generating care. Preservation of when N95 masks are in short supply, they should be conserved for use with aerosol generating procedures.   

Last Updated: April 3, 2020
Microwave- and Heat-Based Decontamination of N95 Filtering Facepiece Respirators (FFR): A Systematic Review
— Gertsman et al.
Systematic Review

This review found that dry/moist microwave irradiation and heat provides safe and effective decontamination for N95 filtering facepiece respirator (FFR) reuse. Autoclaving is not recommended. All masks should be inspected for physical degradation before reuse.  

Last Updated: August 20, 2020
Safety of Extended Use and Reuse of N95 Respirators
— Emergency Care Research Institute (ECRI)
Rapid Review

In this review, three studies found that autoclaves, steaming, moist heat, bleach, benzalkonium chloride and (UV-C) achieved a 10,000-fold reduction in H5N1, H1N1 and _S. aureus _loads on N95s. In one study ultraviolet germicidal irradiation (UVGI) was ineffective on some N95 models and one study found that inoculation patterns affect UCGI. Studies report mixed results on N95 integrity after more than three cleanings.

Last Updated: March 22, 2020
Anesthesia Informatics and Media Lab: Addressing COVID-19 Face Mask Shortages [v1.3]
— Stanford Medicine- Anesthesia Informatics and Media Lab
Rapid Review

This review notes that the CDC’s National Institute for Occupational Health and Safety (NIOSH) has stated that there is no way of determining the maximum number of safe reuses of an N95 respirator that can be applied in all cases. It is advised that N95 respirators be discarded after an aerosol generating procedure. 

It remains unknown how wearing N95 masks multiple times impacts the fit of the mask.

Last Updated: March 24, 2020
Optimization of N95 Respirator Masks During Supply Shortages – Round-Up
— Canadian Agency for Drugs and Technologies in Health (CADTH)
Rapid Review

This review found that effective strategies for managing supply of N95 masks include: layering (i.e. use a face shield, surgical mask or other disposable cover), extended use (maximum recommended vary 6-12h) and rotating (use a five-day rotation schedule for each mask).     Effective strategies for reprocessing N95 FFRs must inactivate the virus, without damaging the filtration or the fit of the respirator as well as making it safe to wearer. As stated by the CDC, the most promising reprocessing techniques to date are the following: UV germicidal irradiation with UV-C light, vaporized hydrogen peroxide, moist heat or steam and dry heat.  

Last Updated: October 15, 2020
Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare Settings
— CDC: Centers for Disease Control and Prevention
National Guidance

The CDC advises that extended use is more effective than re-use. Extended use should cease after exposure to aerosol generating procedures, fluid contamination, or contact with infectious patients. 

Re-use of respirators should ensure that users are re-using their own masks. The number of times a mask can be re-used should be based on manufacturer’s guidelines, with some studies suggesting five re-uses as a maximum.

Last Updated: March 26, 2020
Optimizing the use of masks and respirators during the COVID-19 outbreak
— Health Canada
National Guidance

Health Canada suggests that N95 and surgical masks may still be effective if they do not have visible signs of damage, and have intact straps. Re-used N95 masks should be fit-tested and have a seal check. A face shield may also be used to manage short supply of N95 FFRs.

Health Canada has application requirements that manufacturers of mask reprocessing devices must meet before authorization.

Last Updated: October 19, 2020
Authorized medical devices for uses related to COVID-19: List of authorized medical devices other than testing devices
— Health Canada
National Guidance

Health Canada provides a list of authorized manufacturers’ specific decontamination methods for different types of 3M N95 masks. 

Last Updated: October 31, 2020
Decontamination of 3M Filtering Facepiece Respirators, such as N95 Respirators, in the United States – Considerations
— 3M
Manufacturer Guidance

3M outlines aspects of a successful respirator decontamination: 1) inactivates target organism; 2) does not damage filtration; and 3) does not affect fit and safety for the user. Although 3M does not recommend reprocessing single-use respirators, CDC guidance using certain reprocessing methods may be needed when respirators are in short supply. 3M has evaluated several methods that have received FDA approval and those that have not. 

Current findings suggest that ethylene oxide, formaldehyde, ionizing radiation, microwaves, high temperatures, ethanol, isopropanol, soaps and detergents are deemed unsuccessful decontamination methods due to varying factors. 

Last Updated: August 31, 2020
COVID-19: Update from CMA President
— Canadian Medical Association
Organizational Scan Last Updated: March 23, 2020
Personal Protective Equipment (PPE) use during the COVID-19 Pandemic
— Ontario Health Association
Organizational Scan Last Updated: March 29, 2020
PPE Update for Family Physicians from the Ministry of Health/ Ontario Health
— Ontario College of Family Physicians
Organizational Scan Last Updated: August 4, 2020
Prescientx High Volume N95 Mask Disinfector
— Prescientx
Organizational Scan Last Updated: May 3, 2020
Sunnybrook developing N95 mask alternative using full-face snorkel mask
— Sunnybrook Health Sciences Centre
Organizational Scan Last Updated: April 29, 2020
Some hospitals planning to sterilize and reuse N95 masks to stretch out supplies during COVID-19 pandemic
— Sunnybrook Health Sciences Centre
Organizational Scan Last Updated: April 5, 2020
Disclaimer: The summaries provided are distillations of reviews that have synthesized many individual studies. As such, summarized information may not always be applicable to every context. Each piece of evidence is hyperlinked to the original source.

Comments:

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