Built of face mask is key in stopping droplet spread

While analyzing the effectiveness of non-medical face masks in curbing spread of respiratory droplets that could contain viruses, researchers have found that well-fitted homemade masks with multiple layers of quilting fabric and off-the-shelf cone style masks were the most useful, as compared to a loose handkerchief covering or no mask at all.

A study from Florida Atlantic University, in Physics of Fluids, from AIP Publishing, looks to better understand which types are best for controlling respiratory droplets that could contain viruses. Led by Siddhartha Verma and his team, the study experimented with different choices in material and design to determine how well face masks block droplets as they exit the mouth.

Using a laser to detect droplets as they were coughed and sneezed out of a mannequin head, the group was able to map out the paths of droplets and examine how different designs and materials alter that path.

The group found that loosely folded face masks and bandanna-style coverings reduced the distance traveled by the droplet jets between one-eighth to half respectively of that for an uncovered cough. However, well-fitted homemade masks with multiple layers of quilting fabric and off-the-shelf cone style masks proved to be the most effective. Some leakage notwithstanding, these masks reduced the number of droplets significantly, the study findings said.

When without a mask, the mannequins were projecting droplets much farther than the oft-cited 6 feet in social distancing guidelines.

Verma said the group looks to continue studying the complex interplay that can involve droplet evaporation, ambient airflow and properties of the respiratory fluid ejected that lead to how droplets behave.

"It is also important to understand that face coverings are not 100 percent effective in blocking respiratory pathogens. This is why it is imperative that we use a combination of social distancing, face coverings, hand-washing and other recommendations from health care officials until an effective vaccine is released," he said.

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While the use of face masks in public has been widely recommended by public health officials during the current Covid-19 pandemic, there are relatively few specific guidelines pertaining to mask materials and designs. The smallest respiratory droplets leak through a face mask constructed using a folded handkerchief. Despite the leakage, the spread of the droplets is impeded considerably compared to no mask use.