Covid-19 mask fabric has huge impact on effectiveness finds Georgia Tech report

A new study from Georgia Tech found that wearing a face mask can shield you and others from COVID-19, but the number of fabric layers and the type of cloth used can have a huge impact on the risk of exposure.  

Nga Lee (Sally) Ng, who is an associate professor and Tanner Faculty Fellow in the School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences, said that the filtration efficiency of submicron particles moving through a variety of materials was calculated in this analysis. A human hair is approximately 50 microns in diameter, while 1 millimetre is 1,000 microns. She explained, "A submicron particle can stay in the air for hours and days, depending on the ventilation, so if you have a room that is not ventilated or poorly ventilated then these small particles can stay there for a very long period of time."

Georgia study finds 'Fabric layers and material choice on COVID-19 mask matter'

The research was carried out in April 2020, when the pandemic forced the closing of most institutions around the world. Many citizens were forced to make their own homemade masks due to extreme shortages of personal protective equipment in their communities. Ng remembered that Georgia Tech was able to rapidly set up the analysis because it already had "a perfect method for measuring filtration performance using existing lab instruments."

With the findings of the research reported in the journal Aerosol Science and Technology on March 22, the results were used to shape homemade face mask recommendations in April, last year. 

The researchers tested a total of 33 commercially available materials, including single-layer woven fabrics such as cotton and mixed fabrics, woven polyester, nonwoven materials, materials typically used, cellulose-based materials and found in hospitals, and various filter materials, in addition to cloth fabrics. "We learned there was a lot of variability infiltration performance even in the same type of material," Ng said. 

Ryan Lively, who is an associate professor and John H Woody Faculty Fellow in the School of Chemical and Biomolecular Engineering, opined "We found commercially available materials that provide acceptable levels of submicron particle rejection while still maintaining airflow resistance similar to a surgical mask. These materials combine fabric fiber density, a maze-like structure, and fiber surface chemistry to effectively reject submicron particles."

Blackout drapery, sterilisation wrap are best-performing materials for COVID-19 mask

Blackout drapery and sterilisation wrap, which is usually used to pack surgical instruments, was the best-performing materials for homemade masks. Both products are available for purchase. People should avoid using HEPA/MERV filters or vacuum bags unless they are certified to be fibreglass-free, according to the researchers, since such filters can emit glass fibres that can be inhaled. Loose-knitted material, fleece, batting cloth, felt and glossy, reusable shopping bags are all materials to avoid for masks.

Multilayered samples outperformed single-layer samples substantially, but breathability should be considered. For submicron particles, the filtration performance of the two-layered and three-layered samples tested was about 50%. Particles can easily escape through holes in the nose or the sides of the mask, so proper mask fit is essential.

When one person wears a correctly fitted and multilayer mask, it rejects 84% of particles expelled by that person. When two people wear these masks, particle transmission is decreased by 96%. The value of universal mask-wearing was the final outcome of the study.

Ng asserted, "The best way to protect ourselves and others is to reduce exhaled particles at the source, and the source is our face. That really gets amplified when everyone starts wearing masks. Not everyone understands the importance of airborne virus transmission, and the importance of wearing a mask. Ng added, "I hope that the practice will continue to help reduce the release of these viral particles into the environment and help protect others." She expressed hope that the results would encourage more people to wear masks when they are sick and need to be in public.

(with inputs from ANI)

(Picture Credit: Unsplash/Representational Image)