Face masks vs face shields: Here’s what you need to know
Experts on why wearing face shields without a mask underneath may not be the best option
How often do you see people wearing only face shields made of plastic and no mask? While stepping out with only face shields on may seem like a more comfortable option than wearing tight-fitting face masks like N95, they may be completely ineffective if a recent study is to go by.
As per Japanese government-backed research using the world’s fastest computer Fugaku, it has been shown that “almost 100 per cent of airborne droplets of less than five micrometres escaped through the gap between the face and the face shield”. The research further concluded that about half of larger droplets, measuring up to 50 micrometres, also found their way into the air, and the shields were able to trap droplets only larger than 50 micrometres.
Led by Riken, a scientific research institute in Japan, the study combined airflow with the reproduction of tens of thousands of droplets of different sizes for the experiment, like what is prevalent in these times of COVID-19.
“Judging from the results of the simulation, unfortunately, the effectiveness of face guards in preventing droplets from spreading from an infected person’s mouth is limited compared with masks,” Makoto Tsubokura, team leader at Riken’s Centre for Computational Science, told The Guardian.
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Another study published in the journal Physics of Fluids found that although face shields are understood to initially block droplets from a simulated cough, small droplets can easily move around the sides of the visor and eventually spread over a large area. The study was based on visualised experiments that studied the travel patterns of respiratory droplets by attempting to simulate coughing, by connecting a mannequin’s head to a fog machine, and then, used a pump to expel vapour through the mannequin’s mouth.
In fact, much before this pandemic, a 2014 study published in Journal of Occupational and Environmental Hygiene, ‘Efficacy of face shields against cough aerosol droplets from a cough simulator’, observed that while face shields can substantially reduce the short-term exposure of healthcare workers to ‘large infectious aerosol particles’, smaller particles can remain airborne longer and flow around the face shield more easily to be inhaled. ‘Thus, face shields provide a useful adjunct to respiratory protection for workers caring for patients with respiratory infections. However, they cannot be used as a substitute for respiratory protection when it is needed.’
Agreed Dr Tushar Rane, internal medicine expert, Apollo Spectra Hospital Mumbai. “Face shields made of plastic provide for a good barrier against airborne infection like coronavirus infection. A standard face shield usually extends well beyond the chin and is made of plastic material. Although the face shields provide good protection in an open place, it may fail to provide adequate protection in a crowded place or in a healthcare facility where the chances of getting exposed to the virus are greater. Whereas, a snugly fitting face mask such as N95 mask or a three-ply surgical mask if worn properly should provide for adequate protection against such exposures. One has to be always cautious, not to reposition or keep touching the mask so as to reduce the chances of exposure. In a healthcare facility, it is always preferable to use a face mask and a face shield for better protection from exposure to the virus,” he told indianexpress.com.
When this accessory becomes par for course, so does this kind of selfie.. ? ?
A post shared by Mandira Bedi (@mandirabedi) on
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Not just the comfort, people are beginning to rely on face shields because they allow one’s facial expressions to be visible over face masks. However, rather than face mask vs face shield view, it is necessary to have both in place, say experts. “Proper wearing of masks is essential to reduce the risk of infection. The face shield helps in preventing large droplets but the small droplets would still find their way in the lungs if a person is not wearing a mask. Face shield may be used as an extra precaution with a face mask,” said Dr Manoj Goel, director, pulmonology, Fortis Memorial Research Institute, Gurugram.
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