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Face shields useless?
Posted: Sun Jul 19, 2020 8:17 pm
by Brightonian
Swiss government warns against face shields.
Health officials in the canton of Graübunden studying a recent outbreak among staff at a hotel found a worrying trend - all of those who were infected wore plastic face shields, while those who avoided infection wore face masks.
Re: Face shields useless?
Posted: Mon Jul 20, 2020 11:39 am
by Sciolus
My understanding is that face shields offer some protection if people are talking directly into your face, and therefore spraying coarse droplets onto your face; but they're obviously useless against aerosols and suspended droplets. Likewise the screens at shop tills, which are a reasonable precaution given the prevalence of face-to-face talking here.
Re: Face shields useless?
Posted: Tue Jul 21, 2020 10:32 am
by Martin Y
I can't help wondering if this result also reflects the different work being done by mask-wearers and shield-wearers. Were they giving serving staff face shield rather than masks so they were less intimidating to customers/guests or so they could be heard better? If you do that then your shield-wearing staff are also the ones who interact with the most different people.
Re: Face shields useless?
Posted: Tue Jul 21, 2020 7:14 pm
by sTeamTraen
Why is the discussion about the relative protection afforded to the wearer, when the entire story of mask wearing is that anything short of an N95 mask is only useful to protect others? Did I miss a memo? I mean, it would be great if regular (disposable surgical or cloth) masks did protect the wearer, and one can easily imagine that they might, but that whole article reads as if everybody involved expects face coverings to protect the wearer, and is disappointed that shields failed.
Oh, and the sample size is reported as "several". Let me just take the square root of that and calculate the standard error.
Re: Face shields useless?
Posted: Tue Jul 21, 2020 8:07 pm
by Sciolus
Well, I would expect that shields and screens provide (some) protection for both parties with regard to the specific transmission pathway I mentioned. Masks are a different matter.
Re: Face shields useless?
Posted: Wed Jul 22, 2020 4:19 pm
by raven
Well... d'uh?
I thought the whole point of face shields was that they prevent direct droplet splatter into the eyes and they're mostly of use in addition to masks in hospital/care settings where staff are exposed to that kind of thing during procedures that create aerosols, and when they have to get up close & personal with patients who are ill and coughing....
I can't see face shields being much use in shops or bars, where the risk is mostly from droplets/aerosol exhaled by customers and then inhaled by staff. A visor doesn't filter the air you breathe in.
It also doesn't stop you scratching your nose or picking your teeth. Which is perhaps the main way masks protect the wearer, although I've seen people pull down masks to do that anyway.
Re: Face shields useless?
Posted: Thu Jul 23, 2020 5:40 am
by RoMo
raven wrote: ↑Wed Jul 22, 2020 4:19 pm
Well... d'uh?
I thought the whole point of face shields was that they prevent direct droplet splatter into the eyes and they're mostly of use in addition to masks in hospital/care settings where staff are exposed to that kind of thing during procedures that create aerosols, and when they have to get up close & personal with patients who are ill and coughing....
I can't see face shields being much use in shops or bars, where the risk is mostly from droplets/aerosol exhaled by customers and then inhaled by staff. A visor doesn't filter the air you breathe in.
It also doesn't stop you scratching your nose or picking your teeth. Which is perhaps the main way masks protect the wearer, although I've seen people pull down masks to do that anyway.
That's what I thought as well, but government guideline for close contact services specifically says "advise workers to wear visors when working within 2 metres of clients"
Re: Face shields useless?
Posted: Fri Jul 24, 2020 8:45 pm
by raven
RoMo wrote: ↑Thu Jul 23, 2020 5:40 am
That's what I thought as well, but government guideline for close contact services specifically says "advise workers to wear visors when working within 2 metres of clients"
Oh. It does, doesn't it. And it says:
This should take the form of a clear visor that covers the face and provides a barrier between the wearer and the client from respiratory droplets caused by sneezing, coughing or speaking.
So I guess they're working on the assumption it's spread by droplet & not aerosol, so a visor is adequate. But there's some evidence for aerosol spread under some circumstances I think, so I'd have thought you'd want a mask as well. But maybe they've decided droplets are the bigger risk so protecting against that is more important...