Simulations confirm face masks suppress the spread of COVID-19

Face masks are recommended to prevent the spread of the COVID-19 virus through breathing, coughing, and sneezing. Khosronejad et al. provide science to back this recommendation.

The authors conducted the most realistic and highest resolution computational fluid dynamics simulations to date of saliva particle transport during coughing with and without masks. The simulations considered the effect of human anatomy, a range of particle sizes, and both medical and non-medical grade masks. Each simulation required over 500 CPU hours and took over four months to complete.

They found that wearing a non-medical grade mask indoors, which was represented by a stagnant ambient flow, can suppress the spread of saliva particles from a cough to about 0.70 meters (or 0.48 meters with a medical-grade mask), but without a mask particles can travel over 2.50 meters and stay in the air for long periods of time. Outdoors, which was represented by a mild breeze, the effectiveness of facial masks decreases because saliva particles from a cough travel too fast.

The authors argue that individuals should wear masks while indoors to protect others from virus-laden saliva particles and wear masks while outdoors to protect themselves.

“Our work is extremely important in the sense that it can help officials and stakeholders to know the importance of mask-wearing under outside conditions,” said author Ali Khosronejad. “Right now, the public thinks that no one needs to wear a mask while one is outside. Our finding shows that they should wear masks to protect themselves from saliva particles flying in the air.”

The authors are currently studying the effectiveness of masks in suppressing saliva particles during normal breathing.

Source: “Fluid dynamics simulations show that facial masks can suppress the spread of COVID-19 in indoor environments,” by Ali Khosronejad, Christian Santoni, Kevin Flora, Zexia Zhang, Seokkoo Kang, Seyedmehdi Payabvash, and Fotis Sotiropoulos, AIP Advances (2020). The article can be accessed at https://doi.org/10.1063/5.0035414 .