The COVID-19 pandemic increases demand for PPE, including face masks. Reusing and disinfecting masks can help meet demand. H1N1 without chemicals can be inactivated by UV light. We found that 254 and 265 nm UV-C irradiation at 1 and 10 J/cm2 did not affect N95-rated masks’ ability to remove virus-sized particles. Multiple mask layers did not change polymer structure, morphology, surface hydrophobicity, pressure, or tensile strength. Low-pressure UV lamps and 265 nm LEDs were similar. Based on healthcare worker input and our findings, we designed a treatment method and operational manual to treat and reuse N95 masks. This work can help with techno-economic studies on cleaning and reusing masks or lifecycle assessments of single-use PPE waste in healthcare, especially during pandemics. We’ll walk you through all you need to know about N95 masks and UV-C light as the most effective methods to disinfect.
Ultraviolet Light Can Clean N95 Masks for Reuse Without Hindering Performance, NIST Study Shows
In what is perhaps the most rigorous examination of UV light’s effects on N95 masks yet, researchers at the National Institute of Standards and Technology (NIST) have shown that these masks can be disinfected with very little impact on either their form or their function. This is an important step forward in the fight against the spread of infectious diseases. In a new study that was recently published in the Journal of Research of the National Institute of Standards and Technology, the researchers, with assistance from federal and private partners, examined UV-exposed N95 masks for traces of viruses and looked for changes in the shape of their fibers, as well as their ability to filter out aerosols and other properties.
The results of this study were published with the results of another study that the same researchers had done. The findings provide an important step in formulating UV standards, the implementation of which may have far-reaching advantages in the foreseeable future. Dianne Poster, a research chemist at NIST and a senior consultant at the organization who was also a co-author of the paper, said that “right now, ultraviolet technologies are basically in their infancy with regard to the health care setting.” And the statistics in this study could be a big help in making these applications more common.
Masks meeting the N95 standard provide an excellent line of protection against infectious respiratory diseases. The “95” in “N95” refers to the mask’s capacity to trap at least 95% of particles as tiny as 75 nanometers (billionths of a meter) that may house hazardous agents such as the coronavirus. This is the minimum level of protection that the mask is required to provide.
But, despite having a good design, the Nokia N95 was only ever meant to be used for one thing. When COVID-19 first emerged in the United States in 2020, the demand for personal protective equipment (PPE) far exceeded the supply available. Because of this, health care workers used a variety of methods to clean masks and other PPE. One of these methods was UV-C light, which is a type of UV radiation that is often used to kill germs.
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Scientific research backs up the applications. However, because of the quick and broad application of the technology toward N95 masks, it was thrown into an unknown area, where there was little understood about how to efficiently utilize the technology.
NIST teamed up with UV-Concepts, a company that makes UV-C systems that aren’t currently sold for disinfecting N95 masks, and Resin nova Laboratories, a company that tests for antimicrobials, to learn more about how UV-C could be used to clean N95 masks.
The authors of the current research affixed N95 masks to racks inside a UV-Concepts system, which is an enclosure lined with 19 UV-C lamps and covered with a reflective surface. They then exposed each mask to UV light for three minutes, ten times each, throughout the course of the experiment.
The group infected some of the masks with OC43, a human coronavirus that is a close cousin of the virus that causes COVID-19. The infected solution was sprayed on the masks by the team. After the irradiation, they counted the number of OC43 viruses that were still active and discovered that the approach sterilized the N95 masks properly across all three layers of the masks, even rendering up to one hundred percent of the viral particles in certain locations inactive.
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The effectiveness of N95 masks, on the other hand, is not reliant on whether or not they have been sterilized; rather, it is determined only by how well the masks operate.
It is unknown whether the wavelength of UV-C used to inactivate a virus releases chemicals, such as ozone, that could potentially affect the plastic used in N95 masks; however, there is a possibility that this is the case. However, doing the check is very necessary, “said John Wright, a researcher at NIST and a co-author of the article.
In order to evaluate whether or not the irradiation had impacted the N95 masks on a global level as well as on a fiber-by-fiber basis, the authors put the masks through a series of tests and put them under a range of different types of stress.
When investigating the fibers, the team used a technique known as scanning electron microscopy, an imaging method. Using this technique, we were able to magnify photographs of the masks by a factor of 2,000 or more, depending on the particulars of the situation. The photographs showed that there were no significant differences between the groups in terms of the fiber size or shape throughout all three layers of both irradiated and no irradiated masks.
In instances when the ultraviolet light affected more than what could be seen via the microscope, the authors looked for additional probable regions in which the changes may have taken place.
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According to Wright, the researchers sought to discover whether or not exposure to UV made it more difficult to breathe while wearing N95 masks, so they tested how effectively the masks resisted air going through them. In other words, they measured how well the masks resisted air passing through them. On the other hand, exposure to UV light did not seem to have any impact at all.
Additionally, the NIST team evaluated whether or not the irradiation had an effect on the filtering capabilities of the N95s as well as the mechanical properties of the gloves. In order to determine the former, they directed a stream of salt-carrying aerosols (resembling the size of particles that are breathed) towards the masks and assessed the number of particles that were able to pass through. They used something called a mechanical tester and pressed on strips cut from the masks in order to make the computation of the latter process easier. The strips had been cut from the masks. Again, the irradiated masks did not show any symptoms of alteration after being exposed to the radiation.
In addition, professionals from the Centers for Disease Control and Prevention’s National Institute for Occupational Safety and Health (NIOSH) examined N95 masks while they were being irradiated in the enclosures. But even though they used different ways to look at some of the same things that the NIST team did, like how well the mask fit, and some other things that the NIST team didn’t look at, they both came to the same conclusion.
Researchers and members of the UV industry may utilize the data that was supplied by the authors in the future to take the initial steps toward understanding how varying levels of UV-C radiation impact the performance and cleanliness of an N95 mask. Having this level of comprehension is necessary in order to standardize these procedures.
In addition, the findings of the study indicate that collaboration is helpful in circumstances in which conventional methods are constrained and there is a need for a large number of experts, skills, and facilities that cut across a variety of sectors.
One technique to help cut down on the amount of trash created by the biomedical industry is to reuse face masks. In the future, research should focus on filling critical technical gaps and conducting both techno-economic (TEA) and life cycle analysis (LCA) studies. This will allow for a better understanding of the extent to which treating and reusing facial masks in normal healthcare operations is beneficial and sustainable.
In order to have a deeper understanding of the scenario, this will be carried out (i.e., non-shortage situations). When it comes to the functional unit of a face mask, one of the most important considerations is the amount of energy required to give a disinfecting dosage of UV-C and the number of times a mask may be used before it needs to be thrown away.
This is because the amount of energy required to give a dosage of UV-C varies depending on the type of mask. 18 There is still a lot of uncertainty about the required UV-C dosage, which can range from 1 to 10 J/cm2 to achieve a reduction of more than 99.9% in recoverable viruses when using N95 masks to less than 50 mg/cm2 to achieve the same level of inactivation as was reported for other surfaces.
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This dosage range is necessary in order to achieve a reduction of more than 99.9% in recoverable viruses. 13,14,30 A study has to be done in order to quantify surface effects and determine whether or not higher UV-C doses are capable of penetrating the polymer layers that are used in N95 masks. This research is important in order to establish the answer to this question.
According to the findings of some studies, UV-C exposures that are greater than 950 J/cm2 do not result in any change in the pressure drops of an N95 mask. As a consequence of this, it is possible that this number represents an upper limit on the cumulative lifespan of exposures before masks need to be discarded. It is required to do research on the effects of recurrent and consecutive UV-C treatments in order to carry out a life cycle assessment (LCA). In the same line, rigorous life cycle analyses would compare and contrast many different disinfection techniques with UV-C therapy (e.g., heat, aerosolized H2O2, and ClO2).
In light of the many innovative ideas that have surfaced in the course of the pandemic, it is possible that N95 masks might be modified for the purpose of treatment and reuse as an alternative to masks that were designed from the outset to be used only once. It would thus be possible to clean the masks in between usage thanks to this. To lessen the impact that PPE has on the natural world, life-cycle assessments (LCAs) of various strategies for cutting down on biological waste might be carried out.
“UV standards developed by collaborations such as these can help us adapt to the next issue we encounter when the PPE supply chain is strained,” said Poster. “[T]his might help us react to the next problem we face when the PPE supply chain is stretched.” “This may be of use to us in responding to the next disaster that we face.”
