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Hi Jayne
Are 2 Masks Better Than 1 at Preventing COVID-19 Spread? (healthline.com)
This is taken from the popular press, so take it as you will, but this part makes physiological and mechanical sense to me:
Binghamton University mechanical engineering assistant professor Scott Schiffres, PhD, who’s been working on testing masks since the COVID-19 pandemic began, said that increasing protection isn’t just about adding more layers of filtration.
If the masks are worn in a way that compromises the fit of the masks on the face, this may allow unfiltered air to leak through gaps.
For example, wearing two surgical masks won’t be better than one, Schiffres said.
“It is not the ability of the filter that limits performance,” he said, “but the fit to the face (how much air leaks at the face seal).”
“The surgical mask material itself is very good (>95 percent at 0.1 um), but in practice about 20 percent of the air will slip between the mask and the seal of the mask, so the efficiency would effectively be about 80 percent,” Schiffres said.
“If you were to just put two surgical masks one on top of another, more of the air would actually leak around the seal as the resistance through the masks increases, and even less air would be filtered, making this double masking detrimental,” he said.
“The most important thing,” Schiffres said, “is not to have a false sense of confidence in the filtration of the mask, as it can only be as good as the fit to your face allows.”
As Kareen has pointed out, CDC does recommend double masking with cloth masks, as filtration is definitely increased, especially if you have two 2-layer masks (many cloth masks commercially sold in the US are 2 layer rather than 3).
Cheers
Michael
Michael Wishart | Infection Control Coordinator, CICP-E
St Vincent’s Private Hospital Northside | 627 Rode Road CHERMSIDE QLD 4032
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Hi Brains Trust,
Have you noticed staff wearing double surgical masks? I have noticed this practice recently and just looking for evidence to refer to when discussing with staff that think it is a good idea?.
Many Thanks in advance
Jayne
Jayne O’Connor RN ,BSc.,Inf.Cont
IPC Co-Ordinator
Sydney Adventist Hospital | 185 Fox Valley Road, Wahroonga, NSW 2076
p: +61 2 9480 9732 | f: +61 2 9470 8052 | m: +61 0406 752685 | e: jayne.oconnor@sah.org.au
http://www.sah.org.au
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