New research: anti-coronavirus masks and social distancing are not enough

Reporter : Mujian / Editor : Zhang Xinyan / Publisher : The Epoch Times / https://www.ntdtv.com/gb/2020/10/28/a102973531.html / Extract translation, editing : Gan Yung Chyan, KUCINTA SETIA

During the ongoing global covid pandemic, wearing masks and maintaining social distance are common prevention methods but a new study found that although these two measures are effective, they are not enough.

The understanding of droplet transmission is based on research decades ago

The scientific basis for wearing masks and maintaining social distancing to prevent droplet transmission is based on research decades ago. Recently, research teams from the Vienna University of Technology, the University of Florida, the Sorbonne University and the Massachusetts Institute of Technology have jointly developed a new droplet propagation model using fluid dynamics.

"Our understanding of droplet propagation is derived from measurements in the 1930s and 1940s." said Alfredo Soldati, a professor at the Institute of Fluid Mechanics and Heat Transfer at the Vienna University of Technology. "At that time, the measurement method was not as good as today, especially the small droplet test, which may not be as accurate and reliable."

The past measurement method believed that when an infected person sprayed droplets, the large droplets would fall to the ground due to gravity, and the small droplets would spray straight ahead but evaporate quickly.

"This depiction is too simple," Soldati said.

Virus droplets entering the air will spread farther and stay longer

In fact, the situation after spraying droplets into the air is quite complicated. Soldati pointed out that although the moisture of the small droplets has evaporated, there are still aerosol particles in the air, which may contain viruses. This allows the virus to spread several meters away and stay in the air for a long time.

Generally speaking, the average diameter of small droplets is 10 microns, and it takes about 15 minutes to fall to the ground. Therefore, even if you observe social distancing, you may be exposed to the virus, such as taking the elevator that the infected person has just taken. Environments with high humidity are more risky, such as conference rooms with poor ventilation.

The Vienna University of Technology stated that although wearing a mask can block large droplets and maintain social distancing is also useful, it should not give a false sense of security. Because even if you wear a mask, the distance and time that the sprayed virus drifts in the air is longer than expected. The new model developed will be able to calculate the concentration of virus droplets at different times and distances.

The research was published in the International Journal of Multiphase Flow.