With masks becoming an integral accessory during the current Covid-19 pandemic, researchers have suggested well-fitted homemade masks with multiple layers of quilting fabric, and off-the-shelf cone-style masks, saying that they have been found to be the most effective in reducing droplet dispersal that could contain viruses.
These masks were able to curtail the speed and range of the respiratory jets significantly, albeit with some leakage through the mask material and from small gaps along the edges, said the researchers in their study published in Physics of Fluids.
However, they cautioned that face coverings are not a 100 per cent 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,” said Scientist Siddhartha Verma and his team from Florida Atlantic University.
The team 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 authors noted the need for further quantitative analysis but were aware of the power of more straightforward visualisation.
“While there are a few prior studies on the effectiveness of medical-grade equipment, we don’t have a lot of information about the cloth-based coverings that are most accessible to us at present,” said Verma. “Our hope is that the visualizations presented in the paper help convey the rationale behind the recommendations for social distancing and using face masks.”
The group found loosely folded face masks and bandana-style coverings had little to no effect on stopping droplet jets. 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.
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.