We know that face-mask-shield don't protect against droplet nuclei which float in the air, so one could end up infected, with COVID-19, even when wearing them.

However the face-mask-shield plus a surgical mask leads to better protection.

Approximately, how much of protection? e.g. 50%, 70%, ?

Additionally, would the protection be improved by extending the borders of the face-mask-shield (the limit is up to the chin)? that is, if one glues a larger piece of plastic to the face-mask-shield?

For example these mask, is there a real difference among them regarding protection?

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    I think this is way too broad and lacks prior research. What disease are you asking about? Ebola? Measles? Whooping cough? COVID-19? It matters.
    – Carey Gregory
    Commented Apr 27, 2020 at 4:37
  • @CareyGregory: Isn't enough by including the covid-19 tag? I am referring to that disease Commented Apr 27, 2020 at 15:52
  • You also added the infectious-diseases tag. Better to spell out in text what you're asking and not rely on tags.
    – Carey Gregory
    Commented Apr 27, 2020 at 19:29
  • @CareyGregory: Ok, I'll edit Commented Apr 28, 2020 at 1:34

1 Answer 1


Any component of PPE is a part of a whole and the protection one gets relates to the environment where one is working. One component doesn't work without the other.

A face shield reduces the amount of virus that then has to get past air tight goggles and a respirator. If a person is in close contact with an infected person then the shield will stop large droplets reaching your face. But smaller droplets and aerosols can bypass the face shield and will then be blocked by the respirator and goggles which have less of a viral load to deal with. Away from the patient the shield is less useful.

Let me summarise the evidence we have found on PPE for healthcare workers to date. First, there is almost no direct evidence on the efficacy of PPE from research studies on COVID-19. Second, there is a lot of indirect evidence from a variety of study designs and real-world data (randomised controlled trials, natural experiments, artificial laboratory studies and more). This evidence varies in quality, and its relevance to the current outbreak is contested. Third, PPE provided to healthcare workers is in short supply and it does not always meet the minimum standards recommended by national and international bodies. Fourth, healthcare workers at the front line are dying.


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