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Prof Claire J. Horwell 😷 Profile picture
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20 Dec 21, 6 tweets, 4 min read
Thanks for the interest in my #mask tweets. For new followers: Pre-covid, I led a large project on effectiveness of #masks for the public, in relation to 🌋 ash exposures. I have extensive experience communicating to the public about mask wearing. ivhhn.org/information #IVHHN
Adding to my pinned tweet with links to each of my mask threads. In the tweet above I link to the 🧵about re-use of disposable masks.
Here, I link to the 🧵about the features of #BetterMasks which enhance comfort and fit:
Here is the 🧵about how the public do not need to be fit-tested in order to wear #BetterMasks (N95/FFP2 etc.)
Here is the 🧵about some healthcare facilities forcing people to wear surgical masks instead of N/FFP masks:
This 🧵is about the fit of #bifold (vertical fold) #FFP2/#N95 masks, especially for small faces: #KidsMasks
Here's my latest 🧵on non-disposable hi-fi masks - different kinds, pros and cons versus disposable ones.

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More from @claire_horwell

Prof Claire J. Horwell 😷 Profile picture
7 Jan
What are 'non-disposable' hi-fi #masks and are they effective respiratory protection? Another short 🧵...

Disclaimer: To demonstrate mask features/types, I will show example images of masks and credit their source. I do not endorse these or any brands, or specific masks.
1/
2/ I will discuss 2 types of non-disposable #facemasks. The 1st has layer/s of #N95/#FFP2 material internally and usually cotton outer layers. They are marketed as being washable & re-usable. The 2nd is called an '#elastomeric' or 'half-face' #respirator. Images: @vogmask @3M ImageImage
3/ Important: if the mask comes with a certification (e.g. CE mark in the UK/EU; NIOSH-CDC label in the US) then they have been tested and fulfil the requirements of relevant product standard e.g. #FFP2/#N95. If this is absent, the mask may use the materials but not be certified.
Read 14 tweets
Prof Claire J. Horwell 😷 Profile picture
5 Jan
Since I posted this tweet, people made suggestions on how to improve fit. Since #bifold #masks are the most commonly available, I decided to try them again, in the context of considering them for my kids who now need to wear masks in school classrooms and communal spaces. 1/
2/ I bought some standard sized #FFP2 bi-fold masks from a major online retailer. 10 masks for £10 - good value. I have a narrow, small face, so quite good analogue for some kids. As soon as they arrived, I could see they would be large on me (photo pre-fitting). Image
3/ I first flattened the nose clip, as people had commented that this sorted out the issue of the masks coming with the nose clip bent in half. This can lead to a 'pinched' clip which lets air in and out between the mask and the bridge of the nose. Image
Read 10 tweets
Prof Claire J. Horwell 😷 Profile picture
1 Jan
Following my @guardianopinion article, people asked which #mask I recommend. I won't recommend a specific brand or model but I can recommend features of masks that will enhance comfort and fit. This🧵relates to industry-certified masks. 1/ theguardian.com/commentisfree/…
#BetterMasks
2/ Firstly, what do I mean by 'industry-certified'? These respirators conform to (and have passed tests for) industry standards of filtration efficiency (at a minimum). To cut a long story short, mainly #N95/N99 (US), #FFP2/FFP3 (Europe/UK) & KF94 (Korea). theguardian.com/commentisfree/…
3/ Although these masks pass tests for how well they filter (capture) particles & aerosol, and all are excellent at doing this, the actual effectiveness of your mask also depends on how well it seals to your face. This also depends on your face shape/size. sciencedirect.com/science/articl… Image
Read 16 tweets
Prof Claire J. Horwell 😷 Profile picture
14 Dec 21
Short🧵on healthcare facilities insisting on the public swapping #N95/#FFP2 #masks with surgical masks on entry. I have heard of this happening in @NHSuk too. Is it a ridiculous request? 1/
2/ I assume that the reason healthcare facilities insist on this is to ensure that people do not enter the facility with contaminated masks and that, for the majority of the public, who are wearing cloth masks, or don't have a mask, a surgical mask will provide better protection.
3/ Let's look at filtration efficiency: #N95/#FFP2 masks are certified to be 95% efficient at capturing particles of 0.3 micron diameter. Surgical masks do not have that certification.
Read 14 tweets
Prof Claire J. Horwell 😷 Profile picture
2 Dec 21
With UK regs changing to mandatory #masks, here's a short 🧵to answer the question: can you wear a disposable #facemask more than once? The answer is YES. Many manufacturers state that masks should be disposed of after 8 hours but this is not true. Read on to find out why ... 1/ Image
2/ Certified #masks (e.g. N95/N99, FFP2/FFP3) are manufactured for workers exposed to harmful airborne particles in industry or healthcare settings. The masks are designed to be worn for one shift (usually 8 hours) and then disposed of. Photo: @3MUK Image
3/ Unless a mask has become clogged full of particles in a very high exposure scenario (e.g. mining, construction) or the worker is in a contaminated front-line healthcare setting, it is still perfectly useable after 8 hours, unless it is broken. Photo: John Hamlett Image
Read 16 tweets
Prof Claire J. Horwell 😷 Profile picture
12 Jul 21
Short 🧵to address this comment. The public do not need to be fit tested in order to wear an FFP3/N99 or FFP2/N95 mask. Here's why: 1/
2/ Fit testing is a procedure which employers are legally obliged to undertake to ensure the safety of workers in dusty industries. It ensures that respirators fit so that workers are protected from the constant exposure to potentially toxic dusts, that they receive over a shift. Image
3/ Whilst it would be great to fit test the public, it is not practical or possible. Nevertheless, FFP2/3 N95/99 masks are widely used, especially in humanitarian crises, by the public and are even donated by major mask manufacturers, for public use, during these crises.
Read 6 tweets

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