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COVID-19 mask research found that layering, material selection is crucial



Covid-19 mask study found that layering, material selection is crucial

Researchers at the Georgia Institute of Technology tested some mask fabric samples. Image source: Georgia Institute of Technology Taekyu Joo

A Georgia Institute of Technology study found that wearing a mask can protect yourself and others from COVID-1

9, but the type of material and the number of fabric layers used can significantly affect the risk of exposure.

The study measured the filtration efficiency of sub-micron particles passing through a variety of different materials. For comparison, the diameter of a human hair is about 50 microns, while the size of 1 millimeter is 1,000 microns.

Nga said: “Depending on the ventilation, sub-micron particles will stay in the air for hours and days. Therefore, if your room is not ventilated or poorly ventilated, these small particles will stay in the air for a long time.” Lee (Sally) Ng, associate professor at the School of Chemical and Biomolecular Engineering and School of Earth and Atmospheric Sciences and a researcher at Tanner College.

The study was conducted in the spring of 2020, when the pandemic triggered the global shutdown of most institutions. The community faces a severe shortage of personal protective equipment, prompting many people to make their own homemade masks. Ng recalled that Georgia Institute of Technology quickly conducted this research because it had “tested an excellent system of filtration efficiency using existing instruments in the laboratory.”

The findings of this study were used here in April last year to shape the recommendations for making homemade facial masks, and the comprehensive study findings were published in the journal on March 22 Aerosol Science and Technology.

The researchers tested a total of 33 different commercially available materials. These materials are not limited to cloth fabrics, including single-layer woven fabrics woven from cotton and polyester fibers, blended fabrics, non-woven materials, cellulose-based materials, and hospitals. Common and used materials, as well as various filter materials.

Ng said: “We have learned that even in the same type of material, there is a big difference in filtration performance.”

Ryan Lively, associate professor in the School of Chemical and Biomolecular Engineering and Fellow of the John H. Woody College, said: “We have discovered commercially available materials that can provide acceptable levels of submicron particle repellency while still remaining similar to surgical masks. The airflow resistance.” “These materials combine the density of fabric fibers, the labyrinth-like structure and the surface chemical composition of the fibers, which can effectively repel sub-micron particles.”

Covid-19 mask study found that layering, material selection is crucial

Graduate student Taekyu Joo established a filtration efficiency measurement system.Image credit: Liu Fubang of Georgia Institute of Technology

The best performance materials for self-made masks are shading cloth and sterilization packaging, which is widely used for packaging surgical instruments. Both materials are commercially available.

Researchers say that people should avoid using filters such as HEPA/MERV or vacuum bags unless they are proven to be free of glass fibers, because such filters usually release respirable glass fibers themselves. Other materials that should be avoided for face masks include loose woven materials, cotton fabric, felt, wool or shiny reusable shopping bags.

The performance of multi-layer samples is much better than single-layer samples, but people should pay attention to air permeability. The tested two-layer and three-layer samples showed an overall filtration efficiency of sub-micron particles of approximately 50%. The fit of the mask is also important because particles can easily escape through the gaps in the nose or the sides of the mask.

Analysis shows that when a person wears a mask, a properly worn multi-layer mask can reject 84% of the particles discharged by a person. Two people wearing these types of masks can reduce the particle transmittance by 96%.

The final point of this study is the importance of wearing general-purpose masks.

Ng said: “The best way to protect yourself and others is to reduce the exhaled particles at the source, and the source is our face. When everyone starts to wear a mask, this situation does magnify.”

She expressed optimism that this discovery will motivate people to use masks more widely when they are sick and need to wear masks in public.

She said: “Not everyone understands the importance of airborne viruses and the importance of wearing masks.” “I hope this approach will continue to help reduce the release of these virus particles into the environment and protect others.”


Research highlights the best styles and fabrics for COVID-19 masks


More information:
Taekyu Joo et al. “Evaluation of particle filtration efficiency of commercially available materials for self-made face masks”, Aerosol Science and Technology (2021). DOI: 10.1080 / 02786826.2021.1905149

Courtesy of Georgia Institute of Technology



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