Despite the fact that people are wearing plastic face shields or masks with a valve, it remains ineffective in preventing the spread of coronavirus when used on its own. This is so as invisible droplets could be sprayed over an extensive area when they sneeze or cough, which defeats the main purpose of a mask.
Based on a report published in the US journal Physics of Fluids on 1st September 2020, vertical and horizontal laser sheets are used by researchers at Florida Atlantic University to track tiny droplets of distilled water and glycerin as they spread from a hollow mannequin head fitted with a plastic face shield or a mask with a breathing valve on it.
The researchers mentioned that though the face shield blocks the movement of the droplets initially, the expelled droplets are still able to move around the visor with relative ease which results in spreading out over a larger area.
Regarding the mask with a valve fitted which supposedly make breathing easier, a large amount of droplets can pass through the exhale valve unfiltered which makes it ineffective in preventing the spread of the Covid-19 virus say that the person wearing the mask is infected.
All in all, the researchers concluded that though both types of ‘mask’ offer higher level of comfort, medical masks of minimal design or high-quality cloth are preferred in delivering effectiveness of prevention of the spread of the virus.
The Straits Times. 2020. Masks With Valves And Face Shields Ineffective, Allow Spread Of Coronavirus: Study. [online] Available at: <> [Accessed 16 September 2020].