TORONTO — A new study from researchers at the University of Illinois suggests that most homemade face coverings do a good job of preventing the spread of respiratory droplets involved in the spread of COVID-19.
Researchers studied the performance of 11 different household fabrics to determine their effectiveness of blocking respiratory droplets. Their findings were published in the journal Extreme Mechanics Letters.
In the lab, researchers tested a range of fabrics from T-shirts, quilts, bedsheets and dish cloths to assess their breathability and droplet-blocking ability. They did this by filling the nozzle of an inhaler with distilled water and fluorescent particles matching the size of a coronavirus particle.
When puffed, the inhaler forced water through the nozzle which then sprayed out droplets over a piece of fabric. Researchers repeated this process multiple times using various materials.
The process revealed that most fabrics have substantial droplet-blocking efficiency, especially cotton fabrics such as T-shirts, which had efficiency levels similar to that of medical masks, while being nearly twice as breathable.
“We found that all of the fabrics tested are considerably effective at blocking the 100 nanometer particles carried by high-velocity droplets similar to those that may be released by speaking, coughing and sneezing, even as a single layer,” professor Taher Saif said in a statement.
“With two or three layers, even the more permeable fabrics, such as T-shirt cloth, achieve droplet-blocking efficiency that is similar to that of a medical mask, while still maintaining comparable or better breathability.
The team of researchers used a high-resolution microscope and high-speed video to measure the size and amount of particles that accumulated with and without the fabric.
“Our study suggests that face coverings, especially with multiple layers may help reduce droplet transmission of respiratory infections,” the report says.
Earlier in the pandemic, Canadian health officials began recommending the use of homemade face coverings when medical grade face masks were scarce. Since then, numerous retailers have stepped up to sell their own face masks online and in stores.
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