FACE SHIELD vs FACE MASK. Effectiveness of Face shield against COVID.

Face shields were present since long, but the covid pandemic brought face shields in light and used by normal population too!! But, What is the effectiveness of face shield in COVID? Can you use face shield instead of  mask? How long can you wear face shield? Can your glasses/goggles work as face shield?
TODAY we will solve all the face shields myths which are confusing people.


DIRECT ANSWER –
FACE SHIELD are an add-on to your MASK. Not a REPLACEMENT.

Many highly consious people started using face shields and face mask both. But some started using only one of the above thinking they both provide equal protection

The importance can be easily undderstood once we understand how diseases like covid spread .

Diseases like covid-19 spread by means of infective droplets. Hence for prevention of this infection, we need to stop the contact of such infective droplets with our eyes, nose and mouth. Face shields provide good protection in this aspect, but can’t be used as a replacement to face mask.


INFECTIVE DROPLETS- 

Whenever a person breaths heavily or speaks or coughs, he/she disperses a considerable amount of droplets into his surrounding environment. These droplets can be of various sizes.

How long these droplets can remain in air or how far these droplets can travel depends on the size of the droplets. 

Larger droplets are heavy and hence can not travel far enough. Such droplets also settle down quickly on surrounding surfaces and can make the surrounding surface infective.

Smaller droplets (aerosols) do not settle easily and remain suspended in air for long time. Such droplets can infect you even if you are far enough from the infected person. 

A healthy individual generates droplets of size between 0.01 and 0.05 micrometer whereas an infectious individual produce droplets between 0.05 and 500 micrometer.

While working in an infective environment, such as a hospital ward filled with infectious patients, it has been found that within 5 min, a worker anywhere in room would be exposed to infectious aerosols released by the patient.

Confused which material is effective in providing your protection against bacteria and viruses? Check out all the answers here 👇.

https://www.medicalmythbuster.info/2020/09/Masks-n95-surgical-cloth-allexplained.html


How CORONA ENTERS OUR BODY

It is necessary to know that corona can enter our body by 3 sites-

  • eyes
  • nose
  • mouth
Now, this can be either direct entry or by indirect way (touching your eyes,nose/ mouth after touching an infected surface)

FACE SHIELD DESIGN-

According to CDC (Centre for Disease Control and prevention), a FACE SHIELD should cover the front and side of the face uptill the ears, so that the tiny droplets do not enter the eyes from the sides.


FACE SHIELD USES AND BENEFITS-

Face Shields provide a transparent protection layer in front of the face so that droplets and aerosols can be prevented  and at the same time the visibility of the user in not hampered.


FACE SHIELD provide an efficient barrier against large droplets. According to the studies these reduced inhalation exposure of worker by 96% and reduced the contamination of mask outer surface by 97%.

BUT  when it comes to smaller droplets or aerosols, face shields block only 68% of cough and 76% of surface contamination. and reduced inhalation by only 23%. Hence, these FAIL to provide enough protection against smaller droplets.

FACE SHIELD ADVANTAGES

Face shields provide protection to your eyes, which the face mask can not provide. Many infections particles such as the COVID-19 virus can enter your body through the mucous membranes of your eyes also. This can occur by direct entry of the virus or by indirect entry (that is touching your eyes after touching an infective surface).

Wearing a Face shield also leads to settlement of less infectious materials on outer surfaces of mask. This provides an additional benefit when the user removes the mask. 

Face shields are re-usable ! These can be used repeatedly till they break or they develop scratches and you have difficulty in vision.


FACE SHIELD DISADVANTAGES-

As discussed earlier, Face sields reduce the short term exposure to large droplets but are not that effective to smaller dropletes or aerosols.

The shield can get scratches over the time of use. This is more if you use cheap quality shields. These scratches can end up creating a visual disturbance and obstruction in sight of the wearer.

Face shields are not easy to carry.

WHEN SHOULD YOU REPLACE YOUR FACE SHIELD?
HOW MANY TMES  CAN U USE IT ?

Generally, face shields are reusable, but there are certain things one should keep in mind for safety-

  • Do not share your face shield
  • Consider sterilizing it using a sanitizer before and after every use
  • If the trasparent plastic of the face shield got scratches and is affecting your visibility, consider changing it


FACE SHIELD vs FACE MASK

are FACE SHIELDS better than FACE MASKS ??

NO

Face shield can never replace your mask !

They just provide an additional layer of protection to your face after face mask.

They provide a protection to your eyes which masks can not provide.

They also reduce the contamination to the outer layers of your mask. This indirectly reduces the the chances of covid infecting you during your process of removing your mask.


FACE SHIELD ARE NEVER AN OPTION TO FACE MASKS

So your preferance should be – face mask and shield > only face mask >  only face shield.

Your regular prescription glasses and contact lenses are NOT to be considered as eye protection.


Check out THE POINTS TO KEEP IN MIND WHILE USING A MASK👇.

https://www.medicalmythbuster.info/2020/04/how-to-use-mask.html


WHEN and WHO SHOULD WEAR A FACE SHIELD?

Medical professionals, especially those working in infective envionments such as covid-19 center and also while performing procedures such as intubation, endoscopy.

Heavy crowded locations.

Caretakers of covid patients.

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SOURCES-

  1. Efficacy of face shields against cough aerosol droplets from a cough simulator” by William G Lindsley and others in J Occup Environ Hyg. 2014.
  2. CDC (centre for disease control) https://www.cdc.gov/niosh/topics/eye/eye-infectious.html
  3. Risk of bacterial exposure to the endoscopist’s face during endoscopy” by Elyse R Johnston and others in Gastrointest Endosc. 2019 Apr.
  4. The role of particle size in aerosolised pathogen transmission: a review” by Jan Gralton and others in J Infect. 2011 Jan.
  5. Dispersion and exposure to a cough-generated aerosol in a simulated medical examination room” by William G Lindsley and others in J Occup Environ Hyg. 2012.
  6. Particle sizes of infectious aerosols: implications for infection control” by Kevin P Fennelly in Lancet Respir Med. 2020 Sep.

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