Wearing face shield alone without masks will not protect people from the novel Coronavirus, reveals the findings of a new study published in the journal Physics of Fluids. The study was conducted in the wake of increasing popularity in the use of face shields by people in public places like restaurants, schools and public transportation.
In the study, researchers assessed what happens to the airflow around a face shield if a person standing one meter in front of him- sneezes. The results showed that the sneeze produces a fluid phenomenon called vortex rings. These vortex rings are capable of capturing microscopic particles and transport them to the edges of the face shield. The synchronisation of these droplets getting attached to the face shield coupled with the time of inhalation of the shield wearer will cause the person to inhale the virus.
Scientists warned that both air flow velocity and vortex rings can enable these droplets to get inside the shield to the vicinity of the nose. Not only during sneezes but even when an infected person speaks thousands of virus particles get released into the air which when inhaled by a healthy person has the potential to infect them.
The plastic face shield is widely used than a mask because of its many advantages like protection of eyes, less fog on glasses while breathing, less risk of people touching faces and more comfort in wearing it.
In the month of July, a Covid-19 outbreak in a hotel in Switzerland proved that all those who were infected were wearing plastic face shields. Swiss government then strictly advised face shield to be worn only in combination with face masks.
WHO has not considered the virus as an airborne one but many scientists now believe it is. Aerosols are more problematic. A tight-fitting mask does reduce the speed of aerosols at the front. A plastic face shield is therefore inadequate in providing protection unless worn with a mask, proves the study.