Although a face mask can offer significant protection against COVID-19 the type of material and how many fabric layers remains incredibly important, researchers have said.

A team from the Georgia Institute of Technology has carried out a series of tests to look at which materials are better at preventing particles spread.

Professor Nga Lee Ng, associate professor and Tanner Faculty Fellow in the School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences, said: “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.”

The trial involved testing 33 different commercially accessible materials and also looking at how different layers impacted the spread of particles.

Professor Ng said: “We learned there was a lot of variability in filtration performance even in the same type of material.”

Professor Ryan Lively Associate, from the John H. Woody Faculty Fellow in the School of Chemical and Biomolecular Engineering, said: “We found commercially available materials that provide acceptable levels of submicron particle rejection while still maintaining air flow 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.”

For people making masks at home, the researchers said that blackout drapery and sterilization wrap, normally used to package surgical instruments, fared well in the study.

Any loose-knitted material should be avoided, as well as felt, fleece, or shiny, reusable shopping bags.

Their research also highlighted the importance of properly fitted masks and those that have multiple layers reject 84 per cent of particles which might be expelled by a person when one person wears it.

Professor Ng added: “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.”

The study findings have been published in the Aerosol Science and Technology journal.

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