
Testing the Efficacy of Homemade Masks: Protection in Influenza Pandemic? (2013) [pdf] - wallflower
https://www.researchgate.net/profile/Katy-Anne_Thompson2/publication/258525804_Testing_the_Efficacy_of_Homemade_Masks_Would_They_Protect_in_an_Influenza_Pandemic/links/53fefd8f0cf21edafd154e85/Testing-the-Efficacy-of-Homemade-Masks-Would-They-Protect-in-an-Influenza-Pandemic.pdf
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svara
We reviewed this and related literature in detail in a pre-print:

[https://medium.com/@matthiassamwald/promoting-simple-do-
it-y...](https://medium.com/@matthiassamwald/promoting-simple-do-it-yourself-
masks-an-urgent-intervention-for-covid-19-mitigation-14da4100f429)

The upshot is, masks work, and the simple ones are particularly effective for
protecting other people from transmission of infectious droplets from the
person wearing the mask.

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RileyJames
I’m about to craft my own mask before getting on a 16 hour flight home to
Melbourne.

I realise it’s fairly ineffective, but I think it will help me avoid touching
my mouth and face.

I have a beard anyway, which I’ve heard makes masks pretty ineffective anyway.

Wish me luck! Haha

Note: I would have bought one... but you know. Everyone else decided their
need for them to sit in their cupboard at home was greater.

Even my need is lower than anyone in a medical position.

~~~
adrianN
Try to find some non-woven fabric like felt, those usually have smaller pore
sizes. And don't forget adding a nose clip. You could also shave.

~~~
imabluedabbad
Going through all that trouble then _not_ shaving is hilarious.

~~~
markdown
Come on, the man wants to look cool at his viewing.

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s1mon
Related similar study: "Simple Respiratory Protection—Evaluation of the
Filtration Performance of Cloth Masks and Common Fabric Materials Against
20–1000 nm Size Particles" talks about SARS and H1N1 sized threats.
[https://academic.oup.com/annweh/article/54/7/789/202744?fbcl...](https://academic.oup.com/annweh/article/54/7/789/202744?fbclid=IwAR1STqBScwET_nBy2T7vnXUioLcnNGeHDyBABRK7NPf4EMW9g5r7Z3PmRVs)

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djzidon
I keep coming back to the fact that the main point of a mask is to prevent you
from touching your own nose and mouth --- NOT to keep the virus from passing
directly to your nose and mouth (or vice versa). Advice from doctor who
studied coronaviruses for 50 years: [https://halegenic.com/coronavirus-
covid-19/](https://halegenic.com/coronavirus-covid-19/)

I do understand, however, that my point is moot when you consider direct
contact with an infected person who is coughing and/or sneezing without cover
(and again vice versa).

~~~
oggy
Interesting, this is the first time I hear that touching fomites is the
primary vector of spreading. The CDC page says the opposite:
[https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmissi...](https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmission.html)
But I do appreciate that we still have a lot to learn about the virus, so
disinfecting your hands frequently and being careful about what you touch is
sound advice.

The other benefit of masks (and probably the main one of DIY masks) would be
that it decreases the chance of the wearer infecting others.

~~~
djzidon
Thank you for sending that. Of course looking at it from both angles couldn't
hurt.

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AltorX
Does anyone know the actual % effectiveness of masks (preferably including
fabrics used in home-made masks)?

It would be an easier sell to people if I could just say ,"it's not 100%
effective but estimates by studies show it to be about 20% effective"

I'm all for this. Can't hurt and might help.

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l_davis
Unless the lockdown ends before covid 19 completely dies out, we should all
think of what we can do to minimize the destruction.

If a mask doesn't harm the wearer, doesn't take away from the supply needed by
medical and other essential personnel, and can help stop or minimize spread
from asymptomatic carriers, why not wear one?

It seems that masks might harm the wearer if warn incorrectly. Well, here's
some information -
[https://www.info.gov.hk/info/sars/en/facemask.htm](https://www.info.gov.hk/info/sars/en/facemask.htm)
\- looks like there are already lots of videos as well. (And they would need
to be adequately cleaned, no question.)

Taking away from essential personnel - don't think that's applicable to cloth
ones.

And i think most studies show they reduce spread of viruses. Probably not
eliminate, but reduce.

So, I certainly intend to wear one - I have 2 on order. And I hope others will
too. It won't solve the entire problem, but it can help.

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hnaccy
I've found the changing mask narrative to be fairly nonsensical. Variations of
the following

\- they're too hard to use so only medical professionals should have them
(including chastising people who had masks laying around for whatever reason)

\- they don't do anything anyways

\- they only stop you from spreading so nobody should wear them in public
(even though asymptotic spreading is known to occur)

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adwi
Does anyone know of a way to be on a list to purchase masks in an ethical
manner? I’d like to get one, but only once the needs of the medical community
are adequately met.

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pibefision
"However, these masks would provide the wearers little protection from
microorganisms from others persons who are infected with respiratory diseases.
As a result, we would not recommend the use of homemade face masks as a method
of reducing transmission of infection from aerosols."

~~~
9oliYQjP
I hear you and understand in theory things like surgical masks allow
coronaviruses to pass through them. But we've got to stop thinking about
wearing masks in absolute terms of "it works" or "it doesn't work". Just like
computer security, wearing a mask is one layer of protection. I don't think
any reasonable person expects a mask to be foolproof. But when used in
conjunction with thorough and frequent hand washing and social distancing
measures, I suspect we'll find that wearing a mask is a prudent thing to do,
even if it's just a home-made one out of cotton pillowcases or a surgical
mask. Masks should not be relied upon in the absence of social distancing and
hand washing just as airbags should not be relied upon without wearing a
seatbelt.

There's anecdotal evidence from places like Taiwan and Hong Kong that masks
are somewhat helpful and very little real evidence that they're harmful except
in terms of making masks unavailable to frontline health workers. I firmly
believe that in hindsight, public health agencies in the west will realize
they did a lot of harm by saying masks were worthless.

~~~
DanBC
> But we've got to stop thinking about wearing masks in absolute terms of "it
> works" or "it doesn't work".

We're not saying that. We're saying masks _make you touch your face_ , and
that without training and correct fitting the minimal protection they give is
probably countered by the increased risk.

[https://www.nih.gov/news-events/news-releases/new-
coronaviru...](https://www.nih.gov/news-events/news-releases/new-coronavirus-
stable-hours-surfaces)

> If the viability of the two coronaviruses is similar, why is SARS-CoV-2
> resulting in more cases? Emerging evidence suggests that people infected
> with SARS-CoV-2 might be spreading virus without recognizing, or prior to
> recognizing, symptoms. This would make disease control measures that were
> effective against SARS-CoV-1 less effective against its successor.

[https://www.nejm.org/doi/10.1056/NEJMc2004973](https://www.nejm.org/doi/10.1056/NEJMc2004973)

> We found that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1
> under the experimental circumstances tested. This indicates that differences
> in the epidemiologic characteristics of these viruses probably arise from
> other factors, including high viral loads in the upper respiratory tract and
> the potential for persons infected with SARS-CoV-2 to shed and transmit the
> virus while asymptomatic.3,4 Our results indicate that aerosol and fomite
> transmission of SARS-CoV-2 is plausible, since the virus can remain viable
> and infectious in aerosols for hours and on surfaces up to days (depending
> on the inoculum shed). These findings echo those with SARS-CoV-1, in which
> these forms of transmission were associated with nosocomial spread and
> super-spreading events,5 and they provide information for pandemic
> mitigation efforts.

~~~
9oliYQjP
I keep hearing that masks make people touch their face. I put to you the
following questions:

1\. Do frontline healthcare workers also "touch [their] face" when wearing
these masks for the same reasons regular people do? I imagine it's to adjust
the fit? If the answer is no, is it because they have been educated not to?
People, at least where I am in Canada, are being told not to touch our faces
already. Can we not just extend the messaging to be "avoid touching your face,
even when wearing a mask"?

2\. If increased face touching when wearing a mask is truly a problem, would
we not expect Hong Kong and Taiwan to have a worse community spread situation?
Why is it that they have this contained? Again, the example is anecdotal. But
coincidentally, they're both locations that learned from SARS and H1N1 and
mask wearing is a foundational part of their public health response.

------
nr2x
Worth noting the authors are from Porton Down:

"Porton Down opened in 1916 as the War Department Experimental Station,
shortly thereafter renamed the Royal Engineers Experimental Station, for
testing chemical weapons in response to German use of this means of war in
1915. The laboratory's remit was to conduct research and development regarding
chemical weapons agents used by the British armed forces in the First World
War, such as chlorine, mustard gas, and phosgene."

[https://en.wikipedia.org/wiki/Porton_Down](https://en.wikipedia.org/wiki/Porton_Down)

------
haunter
Simple Respiratory Mask

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/)

~~~
travisporter
Really grateful for this resource, but the instructions are not exactly clear.
Do you take the t-shirt and make it a single layer of cloth or somehow cut the
shape into "1 outer layer (≈37 cm × 72 cm) rolled and cut as in panel B with 8
inner layers (<18 cm2) placed inside (against the face)." How do the inner
layers stay put?

~~~
dwighttk
looks like the 8 layers are sewn to the single layer. Or possibly the
innermost is sewn to the outermost and the other 7 layers are put in the
resulting pocket.

------
baxtr
_“Our findings suggest that a homemade mask should only be considered as a
last resort to prevent droplet transmission from infected individuals, but it
would be better than no protection.“_

Sounds like common sense

~~~
DanBC
> Sounds like common sense

Unless it causes people to touch their face more.

~~~
njarboe
I don't think touching your face is a problem. It is touching your eyes, nose,
and mouth. When you are wearing a mask you can't touch your mouth and nose.
The "don't touch your face" is a simplification of what people should really
be worried about. Rubbing eyes, touching inside the nose, and in the mouth.
Sometimes this is advice given.

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ummonk
Note that these are results for aerosolized bacteria that tend to hang in the
air. The new coronavirus is only spread via droplet transmission, which would
make even rudimentary masks way more effective.

TL;DR of the results though: homemade mask filtered ~50-70% and surgical mask
~90-95%. Homemade mask reduced transmission into the air by ~75-80%, surgical
mask by ~85%.

~~~
chrischen
I’d imagine at least some of the advice against buying masks is to prevent
hoarding and a supply shortage where they are needed most: healthcare workers.

~~~
adolfojp
The masks can be counterproductive if used without discipline or training.
It's not uncommon to see people adjusting their masks and scratching
underneath them constantly. The masks are transformed into virus concentrators
and rebreathers.

~~~
goodside
Are you aware of any studies on this specifically? Sounds very plausible but
hard to weigh against the benefit of catching expelled droplets. I imagine the
calculus changes depending on age, and whether your primary concern is
preventing your own infection vs. transmission to others.

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ck2
oh wow "vacuum cleaner bag" almost as good as surgical mask

I bought 60 HEPA bags a month before this disaster started.

