Army Research Shows How Do-It-Yourself Facemasks Can Be as Safe as N95shttps://www.defenseone.com/technology/2020/04/army-research-shows-how-do-it-yourself-facemasks-can-be-n95s/164865/Scientists with the Army Research Lab, working with a Massachusetts hospital, have figured out the best easy-to-find materials for making homemade masks: a layer of absorbent cloth combined with a water-repelling fabric, preferably one treated with Scotchgard.... “We really calibrated our technique based on masks that had already been certified,” said Lustig. So far, he reports that they’ve found nine designs that are statistically equivalent to N95 masks — and two that are better.
The ideal made-at-home masks need an absorbent layer composed of something like quilted cotton, terrycloth, dense flannel, a heavy T-shirt, etc. You also need at least one layer that’s hydrophobic, meaning that it repels water, such as a polyester fabric like OLY-Fun, preferably treated with Scotchgard. The more layers you add, alternating back and forth, the better you are protected.
... not all fabrics found around the house are good options for a face mask. Some materials, including furnace filters made of Fiberglas, can send fibers into a person's lungs.-------------------------------
Best Material for Homemade Face Masks May be a Combination of Two Fabricshttps://phys.org/news/2020-04-material-homemade-masks-combination-fabrics.html
Researchers report in ACS Nano that a combination of cotton with natural silk or chiffon can effectively filter out aerosol particles—if the fit is good.
... The researchers used an aerosol mixing chamber to produce particles ranging from 10 nm to 6 μm in diameter. A fan blew the aerosol across various cloth samples at an airflow rate corresponding to a person's respiration at rest, and the team measured the number and size of particles in air before and after passing through the fabric. One layer of a tightly woven cotton sheet combined with two layers of polyester-spandex chiffon—a sheer fabric often used in evening gowns—filtered out the most aerosol particles (80-99%, depending on particle size), with performance close to that of an N95 mask material. Substituting the chiffon with natural silk or flannel, or simply using a cotton quilt with cotton-polyester batting, produced similar results.
The researchers point out that tightly woven fabrics, such as cotton, can act as a mechanical barrier to particles, whereas fabrics that hold a static charge, like certain types of chiffon and natural silk, serve as an electrostatic barrier. However, a 1% gap reduced the filtering efficiency of all masks by half or more, emphasizing the importance of a properly fitted mask.Open Access: https://pubs.acs.org/doi/abs/10.1021/acsnano.0c03252 Abstract:The emergence of a pandemic affecting the respiratory system can result in a significant demand for face masks. This includes the use of cloth masks by large sections of the public, as can be seen during the current global spread of COVID-19. However, there is limited knowledge available on the performance of various commonly available fabrics used in cloth masks. Importantly, there is a need to evaluate filtration efficiencies as a function of aerosol particulate sizes in the 10 nm to 10 μm range, which is particularly relevant for respiratory virus transmission. We have carried out these studies for several common fabrics including cotton, silk, chiffon, flannel, various synthetics, and their combinations. Although the filtration efficiencies for various fabrics when a single layer was used ranged from 5 to 80% and 5 to 95% for particle sizes of <300 nm and >300 nm, respectively, the efficiencies improved when multiple layers were used and when using a specific combination of different fabrics. Filtration efficiencies of the hybrids (such as cotton–silk, cotton–chiffon, cotton–flannel) was >80% (for particles <300 nm) and >90% (for particles >300 nm). We speculate that the enhanced performance of the hybrids is likely due to the combined effect of mechanical and electrostatic-based filtration. Cotton, the most widely used material for cloth masks performs better at higher weave densities (i.e., thread count) and can make a significant difference in filtration efficiencies.
Our studies also imply that gaps (as caused by an improper fit of the mask) can result in over a 60% decrease in the filtration efficiency, implying the need for future cloth mask design studies to take into account issues of “fit” and leakage, while allowing the exhaled air to vent efficiently. Overall, we find that combinations of various commonly available fabrics used in cloth masks can potentially provide significant protection against the transmission of aerosol particles.
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Adding A Nylon Stocking Layer Could Boost Protection From Cloth Masks, Study Findshttps://www.npr.org/sections/goatsandsoda/2020/04/22/840146830/adding-a-nylon-stocking-layer-could-boost-protection-from-cloth-masks-study-findResearchers at Northeastern University have found that adding an outer layer made from nylon stockings to a homemade face covering can boost its ability to filter out small particles in the air by creating a tighter seal between the mask and the wearer's face. In some cases, that extra nylon layer helped homemade cloth masks match or exceed the filtering capability of medical-grade surgical masks.
Even the 3M surgical mask performed better with stockings in their study: Testing showed that it went from blocking out 75% of small particles to 90% with the addition of a pantyhose overlayer. By comparison, an N95 respirator, which is designed to create a tight seal around the face, blocks out at least 95% of small particles when worn properly.
"Adding a layer that keeps the mask tight to the face is going to improve the function of any of these masks," Fernandez explains, "because how well they protect us is not only a matter of what material we're using to do the filtering but also how well [the mask] seals to the face, so that we're trying to avoid air making it around the mask into our breathing zone." The pantyhose layer, she says, helps creates a tighter seal around the face to reduce how much air leaks around loose edges — similar to the seal on an N95 respirator.
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How
not to use pantyhose mask
