N95 masks, worn mostly by healthcare workers, are known to offer the highest level of protection against airborne infections, but they still have limitations. N95 masks filter about 85% of particles smaller than 300 nanometres, or nm (1 nm is a billionth part of a metre). SARS-CoV-2, however, is in the size range of 65-125 nm, so some virus particles could slip through N95s.
Now, researchers have developed a membrane that can be attached to a regular N95 mask and replaced when needed. The filter has a smaller pore size than normal N95 masks, potentially blocking more virus particles, they report in the American Chemical Society’s journal ACS Nano.
N95 masks are intended for a single use but, because they are in short supply, many wear the same N95 mask repeatedly. The researchers sought to resolve this problem by developing a membrane that more efficiently filters particles the size of SARS-CoV-2, and one that could be replaced after every use.
When the researchers measured the airflow rate through the filter, they found that for pores tinier than 60 nm (in other words, smaller than SARS-CoV-2), the pores needed to be placed a maximum of 330 nm from each other to achieve good breathability. The membrane also cleans itself.
Source: American Chemical Society
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