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Home-made face masks likely need at least 2 layers to curb COVID-19 spread:
Home-made cloth face masks likely need a minimum of two layers, and preferably three, to prevent the dispersal of viral droplets from the nose and mouth that are associated with the spread of COVID-19, indicates a video case study published online in the journal Thorax.
[...] A team of Australian researchers therefore compared the effectiveness of single and double-layer cloth face coverings (175 g/m² cotton fabric, with a thread count of 170/ inch) with a 3-ply surgical face mask (Bao Thach) at reducing droplet spread.
[...] The video recording showed that the 3-ply surgical face mask was the most effective at reducing airborne droplet dispersal, although even a single layer cloth face covering reduced the droplet spread from speaking.
But a double layer covering was better than a single layer in reducing the droplet spread from coughing and sneezing, the recording showed.
This is just one case, added to which several other factors contribute to the effectiveness of cloth face masks, note the researchers. These include the type of material used, design and fit, as well as the frequency of washing.
Nevertheless, based on their observations, a home made cloth mask with at least two layers is preferable to a single layer mask, they say, adding: "Guidelines on home-made cloth masks should stipulate multiple layers."
And they emphasise: "There is a need for more evidence to inform safer cloth mask design, and countries should ensure adequate manufacturing or procurement of surgical masks."
Journal Reference:
Prateek Bahl, Shovon Bhattacharjee, Charitha de Silva, et al. Face coverings and mask to minimise droplet dispersion and aerosolisation: a video case study [$], Thorax (DOI: 10.1136/thoraxjnl-2020-215748)
(Score: 2) by Dale on Monday July 27 2020, @05:04PM (2 children)
The cloth masks I have someone made are super thick. I can't breath in it for more than about 10 minutes before I feel like I've been out in 100 degree weather for an hour or two. I wear it when I go to the grocery store.
I have a couple I picked up online that are the full face coverings (Guy Fawkes one for example). They are so thin they can't be doing squat to prevent spread either from my breathing or from others to me. I wear it around the common areas of the office. I still don't care for it, but I can tolerate it for most of the day.
If I had to actually wear it all day for prevention I would have to find some other alternative versus what I have. As it stands, my only public exposure is the grocery stores. My office time is almost all solitary with the garbage mask mentioned above for when transitioning through common areas to my car.
How I'm supposed to get my 6 & 9 year old to wear them all day at school in another month or so is not something I'm looking forward to. Since we're in Texas in the Austin suburbs I figure that will expose us all relatively quickly once things get going regardless of the efforts we've put in up to this point.
(Score: 2) by tizan on Monday July 27 2020, @05:48PM (1 child)
Don't forget static bind virus and bacteria to dust and water vapor ...that is why for e.g 3M airfilters work great at filtering microbes etc from the are.
So just don't look at thinness or absolute size of particulate of material that can go through.
If viruses were all free floating only then we're doomed we have to use scuba diving equipmemt !
(Score: 2) by FatPhil on Monday July 27 2020, @08:09PM
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