‘Plastic shields don’t stop Corona Virus’, seeing this heading might be quite shocking for many. The pandemic has brought numerous products into the market. These products claim to prevent Corona virus transmission. One such products produced & used in a larger scale is plastic face shields.
Plastic shields don’t prevent COVID-19:
New research finds that while wearing a surgical face mask like a respirator (N95) can protect against airborne infection, a face shield offers little / no protection. According to the evidence SARS CoV-2, the virus that causes COVID-19, is transmitted when people expel virus-containing droplets when they sneeze or cough. Studies found that breathing or talking can expel droplets containing the virus.
Face shields/ plastic visors are used as means of protection against COVID-19. But several researches have concluded that plastic shields does not act as a barrier against COVID transmission.
In a study undertaken by the Philipps University Marburg in Marburg, Germany compared 32 types of mask used in hospitals, including cloth and surgical masks, respirators and face shields. Masks used for the test included certified (EN 14683 which is EU quality standard) and non certified surgical masks, KN95 respirators.
“To achieve protection against airborne pathogens by mask. It should fit well around the nose and mouth and the ability to filter airborne pathogens from crossing the material,”said Dr. David Hirschwerk .
The conclusion reached after three separate experiments
Measuring filtration efficacy of masks of different materials
Each mask is attached inside an air tight tank an air-collecting tube is placed. Di(2-ethylhexyl) sebacate (DEHS), an aerosol was pumped into the tank. Particle counter is used to count the aerosol particles which are caught in the collecting tube.
The findings of the study are as follows:
- Cloth masks had the lowest average filtration efficacy at 28 percent.
- Then follows noncertified surgical masks at 63 percent.
- Certified surgical masks at 70 percent.
From the specific observations, KN95 respirator material’s filtering capacity was at 94 percent while FFP2 mask material was at 98 percent.
Surgical masks feel the best with respect to breathing and filtration.
By measuring air pressure on both sides of the surgical mask, it has the lowest drop in pressure. This is beneficial in providing least resistance to breathing. Respirator type masks have the highest drop in pressure.
Filtration efficacy of masks when worn over face:
For this experiment masks are placed over “dummy heads”, the difference being the replacement of air-collecting tube with an artificial windpipe. The dummy head had a coating which is similar to that of human skin and head size equal to average American head size.
The following are the observations:
- FFP2 respirators blocked 65 percent of the particles.
- KN95 respirators blocked 41 percent of the particles.
- A type II surgical mask surprisingly blocked 47 percent of particles.
- As expected cloth masks and uncertified masks has the lowest filtration rates at 11.3 and 14.2 respectively.
Was Face Shield’s really Important?
Face Shields were of no importance at all.
“Members of the public should wear certified surgical face masks of good quality rather than cloth masks or face shields, which performed poorly in our study. Respirators are supposed to be reserved for medical staff,” reported Dr. Christian Sterr.
Evidence suggests that SARS CoV-2 is the virus that causes COVID-19. People expel virus-containing droplets (sneeze/ cough) and it is transmitted.
Studies found that breathing or talking can expel droplets containing the virus. These can remain in the room which poses threat to others who will be present.
Hirschwerk emphasized that although face shields might pass as protective equipment, its not suffice to provide protection or resistance against infection in a highly virus contained environment.
Results of the study:
“A surgical mask provides some protection to the wearer, but not as much as an N95 respirator. Since there is the potential for a pathogen like SARS-CoV-2 to cause infection through the membranes associated with the eyes, the face shields can help reduce that risk. Face shields is not enough in high exposure situations,” he mentioned.
Dr. Teresa Murray Amato, chair of emergency medicine at Long Island Jewish in Queens, New York advices on the usage of cloth masks, “The use of N95 for the general public is most likely unnecessary, especially if social distancing can be maintained.”
Choosing masks is the personal preference of individuals. However experts say advice on wearing masks would change based on the findings of the study.
They also added that masks usage would decrease with time thanks to COVID-19 vaccinations provided. People should approach a healthcare professional concerning vaccines and masks.
In conclusion, plastic shields have no value. Plastic shields don’t prevent aerosol. Masks offer the necessary protection. Health care workers advised to use good masks like respirators. The public should follow social distancing with cloth masks.