5 ms·

Testing the Efficacy of Homemade Masks: Protection in Influenza Pandemic? (2013) [pdf]

52 points by wallflower 7y ago

RileyJames 7y ago
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 7y ago
  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 7y ago
    Going through all that trouble then _not_ shaving is hilarious.
    - markdown 7y ago
      Come on, the man wants to look cool at his viewing.
  - deleted 7y ago
    [deleted]
- deleted 7y ago
  [deleted]
- agumonkey 7y ago
  even if imperfect, if they reduce 1) output 2) input 3) social proximity it's already great
  - __s 7y ago
    3 is a neat point as a reminder to people
baxtr 7y ago
“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
- Gibbon1 7y ago
  That what I've been pushing, I don't see any downside considering the alternative for most people is DYI or none. Also wearing a mask, any mask helps normalize wearing masks in public.
- DanBC 7y ago
  > Sounds like common sense Unless it causes people to touch their face more.
  - njarboe 7y ago
    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.
pibefision 7y ago
"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 7y ago
  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.
  - pjscott 7y ago
    Exactly: protection is probabilistic. Hand-washing isn't perfect, social distancing isn't perfect, and therefore in a sense you could say that they also "don't work" -- but they work in the sense that matters, i.e. reducing the spread of the virus.
  - DanBC 7y ago
    > 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-coronavirus-stable-hours-surfaces https://www.nih.gov/news-events/news-releases/new-coronaviru... > 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.
ummonk 7y ago
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 7y ago
  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.
  - jmrko 7y ago
    That's a bad argument against DIY masks though. I tend to also agree with Zeynep Tufekci in this matter: https://www.nytimes.com/2020/03/17/opinion/coronavirus-face-masks.html?action=click&module=Opinion&pgtype=Homepage https://www.nytimes.com/2020/03/17/opinion/coronavirus-face-...
  - deleted 7y ago
    [deleted]
  - adolfojp 7y ago
    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 7y ago
      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.
haunter 7y ago
Simple Respiratory Mask https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/
- travisporter 7y ago
  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 7y ago
    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.
nr2x 7y ago
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
ck2 7y ago
oh wow "vacuum cleaner bag" almost as good as surgical mask I bought 60 HEPA bags a month before this disaster started.
s1mon 7y ago
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?fbclid=IwAR1STqBScwET_nBy2T7vnXUioLcnNGeHDyBABRK7NPf4EMW9g5r7Z3PmRVs https://academic.oup.com/annweh/article/54/7/789/202744?fbcl...
svara 7y ago
We reviewed this and related literature in detail in a pre-print: https://medium.com/@matthiassamwald/promoting-simple-do-it-yourself-masks-an-urgent-intervention-for-covid-19-mitigation-14da4100f429 https://medium.com/@matthiassamwald/promoting-simple-do-it-y... 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.
adwi 7y ago
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.
djzidon 7y ago
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 7y ago
  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/transmission.html https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmissi... 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 7y ago
    Thank you for sending that. Of course looking at it from both angles couldn't hurt.
AltorX 7y ago
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.
hnaccy 7y ago
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)
l_davis 7y ago
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.

52 points by wallflower 7y ago

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 7y ago
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 7y ago
  Going through all that trouble then _not_ shaving is hilarious.
  - markdown 7y ago
    Come on, the man wants to look cool at his viewing.
- deleted 7y ago
  [deleted]
deleted 7y ago
[deleted]
agumonkey 7y ago
even if imperfect, if they reduce 1) output 2) input 3) social proximity it's already great
- __s 7y ago
  3 is a neat point as a reminder to people

baxtr 7y ago

“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

Gibbon1 7y ago
That what I've been pushing, I don't see any downside considering the alternative for most people is DYI or none. Also wearing a mask, any mask helps normalize wearing masks in public.
DanBC 7y ago
> Sounds like common sense Unless it causes people to touch their face more.
- njarboe 7y ago
  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.

pibefision 7y ago

"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 7y ago
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.
- pjscott 7y ago
  Exactly: protection is probabilistic. Hand-washing isn't perfect, social distancing isn't perfect, and therefore in a sense you could say that they also "don't work" -- but they work in the sense that matters, i.e. reducing the spread of the virus.
- DanBC 7y ago
  > 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-coronavirus-stable-hours-surfaces https://www.nih.gov/news-events/news-releases/new-coronaviru... > 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.

ummonk 7y ago

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 7y ago
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.
- jmrko 7y ago
  That's a bad argument against DIY masks though. I tend to also agree with Zeynep Tufekci in this matter: https://www.nytimes.com/2020/03/17/opinion/coronavirus-face-masks.html?action=click&module=Opinion&pgtype=Homepage https://www.nytimes.com/2020/03/17/opinion/coronavirus-face-...
- deleted 7y ago
  [deleted]
- adolfojp 7y ago
  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 7y ago
    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.

haunter 7y ago

Simple Respiratory Mask https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3373043/

travisporter 7y ago
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 7y ago
  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.

nr2x 7y ago

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

ck2 7y ago

oh wow "vacuum cleaner bag" almost as good as surgical mask I bought 60 HEPA bags a month before this disaster started.

s1mon 7y ago

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?fbclid=IwAR1STqBScwET_nBy2T7vnXUioLcnNGeHDyBABRK7NPf4EMW9g5r7Z3PmRVs https://academic.oup.com/annweh/article/54/7/789/202744?fbcl...

svara 7y ago

We reviewed this and related literature in detail in a pre-print: https://medium.com/@matthiassamwald/promoting-simple-do-it-yourself-masks-an-urgent-intervention-for-covid-19-mitigation-14da4100f429 https://medium.com/@matthiassamwald/promoting-simple-do-it-y... 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.

adwi 7y ago

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.

djzidon 7y ago

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 7y ago
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/transmission.html https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmissi... 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 7y ago
  Thank you for sending that. Of course looking at it from both angles couldn't hurt.

AltorX 7y ago

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.

hnaccy 7y ago

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)

l_davis 7y ago

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.