There is a real necessity for repurposing and reusing face masks because of shortages of personal protective equipment (PPE) in the wake of the COVID-19 pandemic. N95 contains a unique filtration media designed for capturing a minimum of 95% particles in the air, including the ones that measure a median of 0.3 m.
Even though the SARS-CoV-2 virus particles are significantly smaller than 0.3 m, they mainly travel through Brownian motion. This allows for their effective capture within the N95 membranes via electrostatic and mechanical forces. However, extended use, reprocessing, and reuse of N95 face masks impacts its filtration capacity.
Re-using N95 Masks
It has been found that coronavirus loses its viability to a significant degree after 72 hours. Visit siteto get N95 masks for yourself. This has prompted several organizations and health agencies around the world to promote a policy of rotation and re-use. CDC statements suggest that N95 masks can be reused for up to 5 times as long as there is no viral contamination or soiling.
In addition, you can make use of any of the following strategies to disinfect and decontaminate the mask:
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Hydrogen Peroxide Vaporization
Hydrogen peroxide vapor (HPV) decontamination is proven in several pilot studies to preserve the functioning of N95 masks while decontaminating them. In fact, the FDA has approved the strategy for N95 decontamination as an emergency method for healthcare personnel.
This decontamination method can only be used on N95 masks, such as 1860 that don’t contain cellulose. Industrial facilities, like Battelle (20 cycles) and hospitals via Steris (10 cycles) and Sterrad (2 cycles) are currently employing this method.
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UV treatment
UV treatment involves full surface area illumination and specific dosing protocols for decontaminating N95 masks. This is to ensure minimal mask degradation with proper inactivation of viral particles. Home UV light is not approved since a high level of precision is required. Many hospital systems in the United States have implementedthis method of N95 mask decontamination.
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Moist Heat
Moist heat, which involves a temperature of 60-70c with a relative humidity level of 80-85% has been shown effective in reducing the efficacy of flu viruses. Data regarding humidity, temperature, and time required for inactivating SARS-CoV-2 viral particles is still limited.
Also, parameters used within moist heat strategy to kill virus strains may potentially affect the mask’s filtration efficacy. This is not a recommended method as of now because of a lack of data.
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Dry Heat
Dry heating is a suggested method of virus decontamination that helps in preserving filter integrity while killing off viruses effectively. This strategy involves heating the mask in low humidity conditions at 70C for a minimum period of 30 minutes.
The United States’ National Institutes of Health (NIH) has recently conducted various tests using SARS-CoV-2. The agency confirms that the method can be used without any adverse effect on mask filtration capacity for up to two cycles. Dry heat doesn’t compromise the N95 mask fit or its filter functions. However, research efforts are still ongoing to identify optimal parameters regarding temperature and duration.
You should note that there are no decontamination recommendations as stated by the CDC. However, CDC has listed Steam and Liquid Hydrogen Peroxide as something that could be made viable pending investigationconclusions.
Health Canada Advisory on Reusing N95 Mask
Health Canada advises that N95 masks should meet effectiveness and safety requirements to be used for protection during aerosol-generating medical procedures (AGMP). In particular, the face masks should be:
- Correctly fitted
- Used with other PPE, like gowns, face shields, and hoods
Also, reusing N95 masks should only be a contingency measure during unavailability due to shortage.
While Health Canada has not approved any methods, there are certain that are featured in the not-approved list. You should not use the following methods for decontaminating your N95 mask for reuse:
- Ethylene oxide (toxic)
- Microwave (metal portion may catch fire)
- Bleach
- Alcohol
- Baking
- Boiling
- Sanitizing wipes
- Soapy Water
Study on Reusing N95 Masks
A US government study, Assessment of N95 respirator decontamination and re-use for SARS-CoV-2, shows that the number of safe reuses of N95 masks varies by the decontamination method. The study states that N95 respirators cannot be safely decontaminated more than 2 – 3 times without undermining their functional integrity.
Both vaporized hydrogen peroxide and ultraviolet light met the bar in the study by reducing the efficiency of SARS-CoV-2. However, this was only for the first two rounds of wear. The study involved observing the effects of decontamination against control respirators. N95 filtration was seen to remain acceptable even after the third round when decontaminated using vaporized hydrogen peroxide and ultraviolet light.
Vincent Munster, Ph.D., chief of the National Institute of Allergy and Infectious Diseases’ Virus Ecology Unit in Hamilton, Montana, and colleagues claimed vaporized hydrogen peroxide to work faster than ultraviolet light.
VHP quickly eliminated the growth of the virus in the exposed media, bringing levels down to zero in 10 minutes. In contrast, ultraviolet light took an hour to bring the virus levels down to an acceptable figure. The study published on the preprint server medRxiv concludes that VHP treatment portrays the most effective and rapid inactivation of SARS-CoV-2 while preserving the integrity of the N95 respirator.
The study took a look at the efficacy of other methods too. They tried decontaminating respirators using heat treatment in a 70C setting on masks that were spray saturated with 70% ethanol solution. They kept the mask in the oven for about 10 minutes and found that while ethanol quickly decontaminated the respirator, it did not pass the respiratory function test on the first round.
Dry heat is slow on its own and can take up to an hour to reach the viral kill threshold. But, dry heat does not interfere with the respirator’s functioning and keeps it effective for up to two rounds of decontamination.
It is important to note that preprint studies are not peer-reviewed. They should not be used as a blind or default guide to clinical practice. A separate study group working on N95 decontamination found that bleach solution, soapy water, overnight storage, and alcohol were suitable. These methods may compromise mask integrity without affecting the virus load.
