The importance of wearing a mask has been repeatedly stressed throughout the Covid-19pandemic. It may have become all the more relevant now, with 239 scientists having written to the World Health Organization about the possibility of airborne transmission of the virus (as reported in The New York Times).
While evidence on such aspects is still emerging, researchers from Florida Atlantic University recently demonstrated a way to check mask performance. Drawing from the principles of fluid mechanics, they used a mannequin to simulate coughs, and tracked the movement of the ejected articles by using a laser. Their results are published in the journal Physics of Fluids.
* Face masks built with a loosely folded handkerchief, as well as bandana-style coverings, showed little capability to stop the smallest aerosolised respiratory droplets.
* Well-fitted homemade masks with multiple layers of fabric, and commercial cone-style masks, curtailed the speed and range of the respiratory jets significantly.
* Even in these homemade masks and cone-shaped masks, a little leakage happened through the material, and from small gaps along the edges.
* In uncovered coughs, droplets were able to travel far beyond 6 feet (the recommended distancing guideline).
What material, and what shape can best arrest droplets from the mouth, and the smallest particles (aerosols), given that not everyone has access to an N-95?
When without a mask, the mannequins were projecting droplets much farther than 6 feet. This distance was reduced by 1/8 when the mannequin wore a loosely folded handkerchief, and by 1/2 when it wore a bandanna-style covering. Well-fitted homemade masks with multiple layers of quilting fabric and off-the-shelf cone-style masks proved the most effective, some leakage notwithstanding.
The bandanna-style mask used was of elastic T-shirt material, the folded handkerchief was of cotton, the stitched mask was of quilting cotton, and the cone-style mask was of random assorted material.
Content for this question contributed by Darrell Morrison, resident of Feeding Hills, Hampden County, Agawam, Massachusetts, USA