Research on Covid-19 masks discovers stratification, material selection problems

In this study, we measured the filtration efficiency of submicron particles that pass through a variety of different materials. For comparison, the diameter of human hair is about 50 microns, while the size of 1 millimeter is 1,000 microns.

“Submicron particles can stay in the air for hours or days depending on the ventilation, so if you have a room that is not ventilated or is poorly ventilated, these small particles will be very It can stay there for a long time, “says Nga. Lee (Sally) Ng, Associate Professor, Tanner Faculty Fellow, Faculty of Chemistry and Biomolecular Engineering and Faculty of Earth and Atmospheric Sciences.

The study was conducted in the spring of 2020, when the pandemic caused the global closure of most institutions. The community faced a significant shortage of personal protective equipment and encouraged many to make their own homemade masks. The Georgia Institute of Technology immediately began its investigation as it already had “a good system for testing filtration efficiency using existing equipment in the lab.”

The findings were used to shape homemade face mask recommendations last April, and comprehensive findings were published in the journal Aerosol Science and Technology on March 22.

Researchers have found 33 types of commercially available fabrics, including single-layer woven fabrics such as cotton and polyester woven fabrics, blended fabrics, non-woven fabrics, cellulose-based materials, and materials commonly found and used in hospitals. I tested the material. Various filter materials.

“I learned that the same type of material has a lot of volatility,” says Ng.

“We have found a commercially available material that offers acceptable levels of submicron particle removal while maintaining the same airflow resistance as a surgical mask,” said Ryan, John H. Woody Faculty Fellow, Associate Professor of Chemistry and Biomolecular Engineering. Lively says. “These materials combine the fiber density of the fabric, the labyrinthine structure, and the chemistry of the fiber surface to effectively eliminate submicron particles.”

The best materials for homemade masks were blackout curtains and sterile wraps, which are widely used for packaging surgical instruments. Both materials are commercially available.

Researchers have stated that filters such as HEPA / MERV and vacuum bags should be avoided unless they are certified fiberglass-free.Other materials to avoid mask Includes loose knit material, batting fabric, felt, fleece, or shiny reusable shopping bags.

Multi-layer samples performed much better than single-layer samples, but attention should be paid to breathability. The two- and three-layer samples tested show that the overall filtration efficiency of submicron particles is about 50%. The fit of the mask is also important because the particles can easily escape through the gaps in the nose and the sides of the mask.

Analysis shows that a properly worn multi-layer mask rejects 84% ​​of the particles emitted by a person when worn by one person. Two people wearing these types of masks reduce particle permeation by 96%.

The final point of the study was the importance of wearing a universal mask.

“The best way to protect yourself and others is to reduce the particles that are exhaled at the source. The source is our face. When everyone starts wearing a mask, it really amplifies.” Ng added.

She expressed optimism that the findings would motivate people to be more widely accepted to wear masks if they were ill and needed to be in public.

“Not everyone understands the importance of aerial viral infections and the importance of wearing a mask,” she said.

She concludes, “I hope this practice helps reduce the release of these viral particles into the environment and protects others.”

This story was published from a news agency feed without changing the text.