This document was updated and re-released April 17, 2020. This content supersedes the previous versions.
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Personal protective equipment (PPE) shortages during the COVID-19 pandemic have precipitated a wave of creative solutions for repurposing of N95 masks. A growing influx of new information can make it difficult to discern best practices for mask re-use. Below we provide resources and tips on this topic. This page will be updated regularly as new information comes in.
Note that based on manufacturer recommendations, N95 masks are designed for one-time use. The CDC and NIOSH do not formally recommend decontamination and re-use of N95 masks, but acknowledge that in times of scarcity, the strategies below are options that can be considered based on individual clinical judgment and the institutional resources available.[1]
How do N95’s work?
The filtration media contained in the N95 is designed to capture at least 95% of particles measuring a median of 0.3 µm. Even though viral particles are a few orders of magnitude smaller than this, nanoparticles mainly travel by Brownian motion and are effectively captured within the N95 filter via mechanical and electrostatic forces.[2] The outer mask material is typically hydrophobic polypropylene. Importantly, extended use, re-use, or re-processing of masks all affect the filtration capacity of the mask.
What are my options for extending the life of my N95 mask?
It is important to differentiate between extended use, re-use, and mask re-processing.
Extended use
The CDC reports that prolonged N95 mask use (including between patients) can be safe for up to 8 hours, and encourages each user to review each manufacturer’s recommendations prior to following this strategy. Current guidelines encourage wearing a face shield over the N95 to decrease the chances of soiling the mask.
Re-use
Because coronaviruses lose their viability significantly after 72 hours[3],[4], many organizations have promoted a rotation and re-use strategy. Assuming there is no soiling and minimal to no viral contamination to the mask, the CDC suggests that masks can be re-used up to 5 times with the following strategy:
Mask Rotation
Acquire a set number of N95 masks (at least 5 per the CDC), and rotate their use each day, allowing them to dry for long enough that the virus is no longer viable (> 72 hours). Proper storage for this technique requires either hanging the respirators to dry, or keeping them in a clean, breathable container like a paper bag between uses. Make sure the masks do not touch each other, and that you do not share your respirator with other people. A user seal check should be performed before each use.
Importantly, when planning to reuse an N-95 mask, practice fastidious donning/doffing to avoid contamination of the inside or outside of the mask at all times (see below methods for donning and doffing). If the mask is damaged or significantly contaminated from aerosol-generating procedures or bodily fluids, the CDC recommends discarding it.
Reprocessing/Decontamination
Mask decontamination strategies are actively being investigated by the CDC, mask companies, and large academic/industry collaboratives. General principles of re-processing include:
- The method must sufficiently inactivate the viral load on the mask.
- The mask cannot be soiled (bodily fluids, makeup[a]).
- The filtration capacity and electrostatic charge must be preserved as much as possible.
- The fit of the mask cannot be compromised.
Most studies on N95 decontamination were performed with flu virus or bacterial spores and cautious extrapolation to the current pandemic is being exercised. Fortunately, recent publications have started to test SARS-CoV-2 specifically, and have found promising results.
Below is a brief summary of the decontamination methods supported by current data. Due to the rapid nature of this research, some publications are not yet peer-reviewed. Additionally, note that there are many versions of N95 masks, with different strap materials and shapes. Thus, one method may work well for one mask type, and not for another.
Hydrogen Peroxide Vaporization
Hydrogen peroxide vapor (HPV) decontamination has been shown in pilot studies to allow multiple cycles of N95 processing with acceptable preservation of function.[5] It is now approved by the FDA as an emergency method for N95 decontamination for healthcare personnel during the COVID-19 pandemic.[6] This method of decontamination can only be used on N95 models that do not contain cellulose, such as the 1860. It is being utilized in industrial facilities such as Battelle (up to 20 cycles) as well as individual hospitals via Sterrad (up to 2 cycles) or Steris equipment (up to 10 cycles).
UV treatment
Proper UV treatment of N95 masks requires specific dosing protocols and full surface area illumination to ensure proper inactivation of viral particles with minimal mask degradation.[7] Due to the precision required, home UV light use is not recommended. This method of decontamination has been implemented by some hospital systems in the United States.[8],[9]
Moist Heat
Moist heat (heating at 60-70°C and 80-85% relative humidity) has been shown to be effective for flu viruses, but there is limited data on the temperature, humidity, and time required to completely inactivate SARS-COV-2 viral particles. Moreover, the parameters required to kill the virus may adversely affect filtration efficacy of the mask. Due to the dearth of specific data on a protocol to achieve both aims, this method is not currently recommended.[10]
Dry Heat
Dry heating of the mask at 70°C for 30 minutes has been suggested as a method of decontamination which can adequately kill virus and preserve the filter integrity for re-use.[11], [12] Recent tests at the NIH utilizing SARS-CoV-2 specifically indicated that this method can be used for two cycles to kill the virus without compromising fit.[13] Research efforts are ongoing to determine optimal parameters (temperature and duration), and this is not yet recommended by the CDC.
My hospital only provides one N95 at a time and I cannot utilize the rotation or decontamination strategies. What are my options?
If your hospital has one-day turnaround capability for the above strategies, this is a potential option. Otherwise, unfortunately there are no at-home strategies recommended by the CDC. The best method is to follow meticulous donning and doffing to avoid touching the inside or outside of the mask, and to prevent soilage. If new methods become available, this section will be updated.
What methods are pending/promising?
The CDC lists a few methods undergoing investigation that may eventually become viable:
- Steam
- Liquid Hydrogen Peroxide
Which methods are NOT approved?
- Bleach
- Alcohol
- Baking
- Boiling
- Ethylene oxide
- May be toxic to the wearer
- Microwave
- At-home microwaving is not recommended because of variable power settings, and metal portions of the masks may catch fire.
- Sanitizing wipes
- Soapy Water
Are there alternatives to N95 Masks?
The CDC recently allowed use of particular non-NIOSH masks from other countries. The approved list is here.
Certain hospital systems have created masks from available hospital materials. These are listed here for informational purposes only, but are not endorsed by the FDA:
Home-made or fashion-industry N95-like masks made from materials such as HEPA filters or fabric are unproven and have potential hazards (HEPA filters may expose the user to fiberglass), and are not recommended at this time.
How do I spot a counterfeit?
The NIOSH has an approved list of N95 vendors that is regularly updated. Check to see if your mask is on this list. The manufacturer of the mask should have certifications readily available for you to view. In addition, there are telltale signs of counterfeits listed on the NIOSH website. Do not use a non-NIOSH mask unless you have ensured it is authentic.
My hospital is no longer doing fit testing, or no longer carries the mask I was originally fitted for. Do I have options for performing a seal check at home?
The CDC does not consider a user seal check an adequate substitute for a fit test.[14]
If you have to wear a new type of N95 mask, a formal fit test is recommended. To ensure that your mask continues to have an adequate seal with repeat uses, the CDC and OSHA recommend performing a user seal check each time the mask is re-used.
Additional Tips
The University of Nebraska has a compilation of PPE protocols available to healthcare personnel that are based on their extensive experience as a National Ebola Training and Education center.
Other problems encountered on the ground include:
- Facial hair is an important consideration when it comes to mask fit. The CDC has recommendations for acceptable configurations. For people who still cannot achieve an adequate seal with an N95, half-face masks or powered air purifying respirators (PAPR) are the next options.[15]
- There are various online videos with methods of donning and doffing that help to minimize contact to the front of the mask. Here is a representative example: https://www.youtube.com/watch?v=EhxpJFDHAeI
Summary
There is no definitive “best practice” for N95 re-use and re-processing. These methods are options for times of crisis and should not be used routinely if mask supply is sufficient. Based on the resources available at each institution, the optimal strategy for each person or institution will vary.
References
[a] Residue on the mask may adversely affect the integrity of the material after re-processing. It is recommended that foundation, sunscreen, or other forms of make-up not be worn underneath.
[1] https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html
[2] https://multimedia.3m.com/mws/media/376179O/nanotechnology-and-respirator-use.pdf
[3] van Doremalen N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 [published online ahead of print, 2020 Mar 17]. N Engl J Med. 2020;10.1056/NEJMc2004973. doi:10.1056/NEJMc2004973
[4] https://www.facs.org/covid-19/ppe/additional
[5] https://www.fda.gov/emergency-preparedness-and-response/mcm-regulatory-science/investigating-decontamination-and-reuse-respirators-public-health-emergencies
[6] https://www.fda.gov/media/136529/download
[7] https://www.n95decon.org/uvc
[8] https://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdf
[9] https://www.wbur.org/commonhealth/2020/03/27/umass-memorial-disinfects-masks-ultraviolet-light
[10] https://www.n95decon.org/heat
[11] https://utrf.tennessee.edu/information-faqs-performance-protection-sterilization-of-masks-against-covid-19/
[12] https://news.stonybrook.edu/sb_medicine/dry-heat-ovens-can-effectively-disinfect-n95-masks/
[13] https://www.medrxiv.org/content/10.1101/2020.04.11.20062018v1
[14] https://www.cdc.gov/niosh/docs/2018-130/pdfs/2018-130.pdf?id=10.26616/NIOSHPUB2018130