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A primary school in Buckinghamshire appears to be the first to require pupils to wear face masks in school:-
Of course the debate over the usefulness of face masks in the face of (so to speak) Covid-19 continues. However, it is not uncommon to also see people wearing, and being advised to wear, not face masks but face-shields, and this article suggests the pupils in this particular school will be allowed to switch from masks to shields for the day in the classroom. But leaving aside the issue of the effectiveness of face masks and the problems to be anticipated in trying to make children under eleven keep them on all day (not to mention swap and share them… good luck with that!)… can anyone actually explain to me the point of wearing a face-shield?
Now I confess that I cannot claim by any means to possess any expertise on either on face masks or shields; my expertise is protective clothing. But in the interests of producing guidance on clothing for Covid protection I have, I think, gained at least some understanding of how it transmits from person to person:-
1. The virus can be suspended in droplets breathed, coughed or sneezed out by a contagious person. These droplets can remain suspended in the air to be breathed in by others.
2. These droplets (or contamination from an infected persons hands) can settle on surfaces and survive for some time. Anyone else can touch the contaminated surface and then transfer the virus to their mouth or nose when they touch their faces (which incidentally is one of the reasons that face masks could potentially make things worse… because being uncomfortable… and in the process of putting them on and taking them off to go in and out of shops – they tend to result in people touching their faces far more often than they would if they were not wearing them, thus increasing the probability of transmission if their hands do become contaminated).
Given these possible routes of contamination I can appreciate that a face mask may be at least partially effective at preventing an infected person breathing (or coughing or sneezing) these infected moisture particles out – the principle being that the mask fabric will “catch” them (assuming the fabric is a sufficiently effective filter). At the same time they will be less effective at preventing people breathing them in because these moisture droplets tend to behave like dust particles; they will move with air flows and unless a perfect seal is achieved around the face mask air will more easily flow through the gaps around it rather than through it – so the droplets will not be “caught” and will be breathed in by the wearer anyway.
But a face shield..?
I can envisage that some limited protection may be provided if an infected person stands six inches from your face (shield) and sneezes at you. In that case the droplets (at least those from your torturers’ mouth – those from his nose will head downwards – see below) will be shooting at high speed in a specific direction (towards your face) with their own kinetic energy. Fortunately however they will be stopped short of your face by the shield.
All well and good. There are however two problems I can see with this theory;
a. the droplets have little in the way of mass and so very limited kinetic energy… you are quite likely to still breath some in around the face-shield in any case
b. In the world we currently live in, if an infected person sneezes at you six inches from your face it is a reasonable assumption that they are doing so deliberately; they are clearly quite determined to infect you and will probably find a way face-shield or not.
Failing this unlikely scenario however I can see no circumstances in which a face shield will make any difference:-
a. From the point of view of the wearer protecting others, unfortunately (or fortunately, depending on which way you look at it) most nostrils point downwards, so the result of breathing or sneezing is to shoot those droplets down below the face shield and into the surrounding atmosphere, and,
b. From the point of view of the wearer being protected from others, the point of a mask is to prevent the wearer breathing in droplets floating in the surrounding environment. These droplets however will follow air flows. When the wearer breathes in the air will simple flow underneath or around the shield and the droplets will follow it, completely ignoring the shield and heading straight up the nasal passageways of the wearer to do its despicable work…
So I am genuinely struggling to see the point of wearing face-shields for Covid protection and if anyone can explain it, please do go right ahead and educate me.
Assuming I am correct however – and again, please do correct me if I have entirely misunderstood the way Covid-19 works – it seems to me that whether from the point of view of a carrier wishing to avoid infecting others or from the point of view of anyone else wishing to avoid being infected – to the Covid-19 virus, a face-shield presents as much of a barrier to transmission as would a Panama hat with a wide brim…
And if this is correct, then please forgive me… but I’ll stick with the Panama… far more stylish…
