NewsCoronavirus

Actions

Keep your distance; new study on coughing shows masks help, not perfect

Keep your distance; new study on coughing shows masks help, not perfect
Posted at 11:40 AM, Jul 08, 2020
and last updated 2020-07-08 12:59:39-04

As the debate about mask mandates continues in some states, a new study reportedly shows social distancing is just as important to reduce the spread of COVID-19. The study looked at the effectiveness of face coverings when someone coughs repeatedly, coughing is one of the symptoms of COVID-19.

The study was published in a June issue of “Physics of Fluid”, by AIP Publishing, and was conducted by Talib Dbouk and Dimitris Drikakis from the University of Nicosia in Cyprus.

The researchers used computer modeling to show the range of saliva droplets when people cough. Previous work from this group showed saliva can travel about 18 feet when a person coughs and is not wearing a mask or covering their mouth.

This new study built on that research to add in the variables of face coverings and repeated coughing. They used information available about filters used in surgical masks.

“The results are alarming. Even when a mask is worn, some droplets can travel a considerable distance, up to 1 meter (roughly 3 feet), during periods of mild coughing. Without a mask, droplets travel twice as far, however, so wearing a mask will help. A mask also decreases the number of droplets that leak out the side of the mask but fails to eliminate it entirely.”
AMERICAN INSTITUTE OF PHYSICS

The computer models found that repeated coughing decreased the efficacy of the face covering, allowing more droplets to eventually get through the mask or around the sides. Those droplets could potentially travel more than 3 feet away from the person. However, the study still found that wearing a mask reduced the spread of droplets, the the amount of droplets expelled into the air.

"The use of a mask will not provide complete protection," Drikakis said. "Therefore, social distancing remains essential." The study also recommended more complete personal protective equipment for those in health care and essential positions, including face shields, gowns and gloves.

MaskStudy2.jpg
A subject coughing in a cyclic incident. A qualitative examination of airborne droplet transmission with and without wearing a surgical mask. The top and bottom figures show the results at 2 s and 3 s, respectively. Wearing a surgical mask that exhibits an initial efficiency of ∼91%. This cannot prevent the transport of the saliva droplets away from the subject. Many droplets penetrate the mask shield and some saliva droplet disease-carrier particles can travel more than 1.2 m. For visualization, the droplets were scaled by a factor of 600 compared to their actual size. The environmental conditions are zero wind speed, ambient temperature 20 °C, pressure 1 atm, and relative humidity 50%. The mouth temperature is 34 °C and the face skin temperature is 32 °C.
MaskStudy1.jpg
A subject coughing in a cyclic incident. Top view of airborne droplet transmission with and without wearing a surgical mask. The top and bottom figures show the results at 4 s and 5 s, respectively. We consider a surgical mask that exhibits an initial efficiency of ∼91%. The cover does not prevent the transport of the saliva droplets entirely away from the subject. Many droplets penetrate the mask shield and some saliva droplet disease-carrier particles can travel more than 1.2 m. For visualization, the droplets were scaled by a factor of 600 compared to their actual size. The environmental conditions are zero wind speed, ambient temperature 20 °C, pressure 1 atm, and relative humidity 50%. The mouth temperature is 34 °C, and the face skin temperature is 32 °C.

Global Coronavirus Tracker:

See map here
Data from The Center for Systems Science and Engineering at Johns Hopkins University.