Updated: Oct 4, 2020
Newly published U.S.-studies help public mask-wearing make sense. But Europe is way ahead of us.
Cloth face-mask science has come a long way in the U.S. since March 2020. More scientific studies have come out describing fabric combinations and layering strategies that provide "excellent filtration efficiency." One study showed that specific multi-layer fabric combinations are excellent at filtering virus-like particles. These studies' results serve to inform makers of cloth face masks. What they don't do is address the intersection where good filtration meets breathability. The WHO's new interim guidance issued June 5, 2020 explains, "Non-medical masks may be made of different combinations of fabrics, layering sequences and available in diverse shapes. Few of these combinations have been systematically evaluated and there is no single design, choice of material, layering or shape among the non-medical masks that are available. The unlimited combination of fabrics and materials results in variable filtration and breathability."
Importantly, WHO referenced cloth mask standards developed by the French Standardization Association (AFNOR Group) to define minimum performance in terms of filtration (minimum 70%) and breathability (maximum resistance upon inhalation and exhalation). Below, a U.S. update that summarizes mainstream CDC recommendations to leave the N95s to health care environment, and do your best to cobble together a home made cloth mask or buy one hoping filtration and breathability is met without standards. That's because none exist in the U.S. when if comes to cloth face masks. New stories on AFNOR and how their tools can be of immense help in the U.S. are coming soon.
So what about N95s used by members of the public outside health care settings? Folks who managed to get their hands on N95 masks during the pandemic so far may not realize that there is a careful "size-selection" and "fit check" procedure that is part of matching which mask-size goes on which worker. Then filtration efficiency is check while the N95 wearer speaks different words and moves different ways. Are we doing that with our face masks? Do most of know that just one gap in a cloth face mask diminishes filtration by 50%?
And then there are the health-care worker bruises----born from 12-hour shifts inside that tight N95 fit needed to protect the worker from patients who are spraying particles toward workers standing less than 2 feet away.
N95s come in different types and sizes----some have 5 layers, some 3 layers. What they have in common is certification by NIOSH for safety compliance, and ASTM provides stringent safety standards. N95 respirators have been rigorously tested for decades to serve the hospital workers and medics who do battle with pathogens, including SARS-CoV-2, on the front lines. Those health care workers HAVE to be close to sick people. We, the public, NO NOT.
Homemade washable cloth face masks, ideally, are not replacements for the N95s and surgical masks reserved for the brave health-care workers helping sick people at less than arms' length away. But certain effectively-made cloth face masks do an excellent job when the wearer is keeping 3 to 6 feet from folks (think strangers) outside their bubble, especially indoors (think shopping). This knowledge makes the pandemic enemy not so mysterious.
Home-made or store-bought face masks can have gaps, be porous, too permeable, not breathable, you get the picture. But those stumbling blocks can be changed. The public can check and correct the fit of their own cloth masks with a bit of effort. And reading the new studies out informs the public on how many layers, which fabrics/materials to choose, and how to ensure fit and breath ability is excellent to the best practices possible.
While your cloth face mask doesn't need to be certified, there is a lot you can do to amp up its caliber in the filtration, breath ability, and no gaps departments. SNS is a great place to start getting educated on how to do that. "My mask protects you and your mask protects me," as authors of one of the latest studies concluded.
The CDC has asked the public's assistance in making cloth masks, and asks that people wear masks in public, particularly indoors, where strangers can get closer than 3 to 6 feet away. We're talking distance from the nearest person who is not in one’s “bubble” aka a stranger. The good news? Washable cloth masks can help reduce viral transmission, even though they are not certified for medical use, the new U.S. studies show--though breathability is not taken into account. Read more via the table of contents on the SNS home page. And keep an out for the new AFNOR coverage coming soon.