22 ms·

Low-cost measurement of facemask efficacy for filtering expelled droplets

107 points by pat2man 6y ago

deleted 6y ago
[deleted]
curiousgal 6y ago
It's kinda sad how the U.S. perceivedly went from conquering space and innovating to getting stuck having basic discussions about climate change, flat earth, vaccination and the effectiveness of face masks. I know it's all on the surface, a vocal minority if you will,and that great science continues to exist and innovation is ever so strong but boy would scientists from the 50s be disappointed if they were to look at the public discourse these days.
- Waterfall 6y ago
  Do you really think everyone in the 50s was in stem, supported the space program, and innvoates? It's always a minority. They were bombing soldiers, us soldiers with nuclear weapons saying it was harmless to see the effects. Is it sad we don't do that anymore? Just because you watch TV and have a bad Facebook feed doesn't make it America
  - adrianN 6y ago
    I think it's important which minority is seen as role model. The cultural narrative is was shapes the next decades.
- 082349872349872 6y ago
  Many US scientists from the 50s hadn't been educated in-country, as they were refugees from the Old World.
- Broken_Hippo 6y ago
  There has been a strong anti-science component in the US for literally centuries. These advances have been despite the sentiment. In addition, it isn't like other countries weren't going to space or weren't working on it (just like now). Tech has been mirrored elsewhere for a long time, but an American education might lead you to believe differently (I know mine didn't really mention that things like cars were being developed elsewhere - they just mention the first American to make things). If you want a fine example of this, look at the push against modern medicine. Folks were eshewing "European-style medicine" for quite some time. The US Took a really, really long time to eliminate lead from paint and gasoline, comparatively, even though we knew about the harm. We knew things about climate change before WWII, and the denial then was pretty strong. People were scoffing about Earth Day when I was a child - I'm 42 now. Anti-maskers were about in the 1910's with the Spanish flu. The anti-vax movement has been around since.. well, around the time we started to have vaccines. Yes, folks lined up for them, but not everyone. It is a whole heck of a lot easier to be vocal about it now, though, and easier to reach others to try to convince them.
  - fpgaminer 6y ago
    Yeah, it's interesting, even the comment you're replying to betrays the duality. 50 years ago the U.S. put a man on the moon, following the coattails of the civil rights movement, meanwhile suffering through one of the most corrupt presidencies, a resurgence of white supremacy that would echo for decades to come, and the beginning of an ignorant war that would destroy the lives of many tens of millions of Americans (the war on drugs). And here we are, today, with an American company SpaceX yet again redefining humanity's reach and we are again suffering through easily the most corrupt presidency to date, white supremacy, and ignorance that is destroying American lives. I think like many it's hard not to look at America today and worry that things are worse than they've ever been. But I think in many ways you're right; America has always been like this. A violent cocktail of the best and worst of humanity, shaken, not stirred.
- mattmanser 6y ago
  I was rewatching Stranger Things last night and Hopper made a comment about how a missing child brings out the crazies (his words, for those somehow not in the know, it's a show set in the 80s, no internet, no mobile phones). I'm starting to suspect that the media, police, government in all its forms, just used to filter them all out. File their reports and letters in the wastebin. I do wonder whether we've now just given those people an ability to talk to the whole world via Twitter/Facebook/etc., who aren't filtering them out. So perhaps the narrative was always there, but pre-internet was easily filtered.
  - codingdave 6y ago
    This is correct - I remember people had serious concerns about it in the early 90s when the web first started growing. It gave a vehicle for "the crazies" to find each other, talk to each other, and strengthen their views by validating each other. In many cases, this is a good thing as it allows a healthy diversity to grow in our society. But it is a double-edged sword. While it does help people find their tribe, it also creates unhealthy echo chambers.
  - brianwawok 6y ago
    They would both filter out the crazies and the Whistleblowers. Bummer we can’t just get the actually useful ones.
pat2man 6y ago
The market for face masks is probably enormous right now but the information out there on which ones to buy is anemic. I assumed this was because masks were such a commodity that it didn't really matter which ones you bought, but this article shows otherwise. Even just among the cotton ones there is quite a difference.
- techsupporter 6y ago
  I think the broader point is one that still stands: wearing literally anything over your nose and mouth is shown, by this study, to cut droplet by at least 50%. Even the cotton varieties cut it from 70% to 90%. So...people need to just slap something over their two air exchanging orifices on their faces before leaving the house and contribute to the our greater health. You're right about the differences in effectiveness but 70% is still pretty good as long as many people are wearing something and not exposing their noses or wrapping the mask lovingly around their chins.
  - Izkata 6y ago
    > wearing literally anything Well, no: the fleece mask broke larger droplets into many smaller ones, resulting in an increase of 10% in the number of droplets compared to the no-mask baseline. Being smaller droplets, they would also hang in the air longer.
    - PierceJoy 6y ago
      Potentially a good thing to keep in mind for the upcoming ski season if people think their fleece face coverings will be effective.
  - Kiro 6y ago
    You touch your face more when adjusting the mask so if it's not efficient enough it may be a net negative. Edit: This is one of the main reason the Scandinavian countries recommend against _all_ mask use (including N95) so not sure why I'm getting downvoted for merely saying an inefficient mask could have that problem.
082349872349872 6y ago
The low-tech way I've seen (but not cross-calibrated), thanks to a pair of argie firemen: use an aerosol spray can, eg hairspray, to see what makes it through the mask candidate.
anonytrary 6y ago
I have an even better way, albeit a bit dirty. Take a vape pen and simply put your mask on before exhaling; "eyeball" the size and trajectories of the exhaled vapor, select the mask that wins, and call it a day.
- bjackman 6y ago
  I don't think there's any reason to assume vapour from a pen resembles the droplets in your breath. In fact, that one of them is visible and the other is not should suggest that they might behave very differently.
  - anonytrary 6y ago
    Mask hole size >> size of o2, n2, co2, and pretty much any aromatic molecule, so I doubt it.
nabla9 6y ago
The number of droplets is just one variable. Slowing down their speed is another. Since droplets are heavy and fall down fast that dry aresols, just having transparent face shield might give protection to others.
carbocation 6y ago
Somewhat off topic, but I think that the figure labeling in this article is disappointing. In figure 2, the masks are numbered but not named. In figure 3, the masks are named but not numbered. So, I can't (personally) tell which mask from figure 1 performed well and which mask performed poorly.
- Merrill 6y ago
  Table 1 gives the relation between mask names and numbers. Having to use the table to relate the pictures to the results does seem very poor.
  - carbocation 6y ago
    Thanks - I had actually missed that on my skim-through.
mhb 6y ago
Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7185834/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7185834/
superkuh 6y ago
Nice to see some empirical validation of valved N95 masks still being better than the vast majority of other "masks" when it comes to protecting other people. And of course valved N95 masks are the gold standard for cheap masks (not full organic vapor gas masks, etc) even outperforming non-valved N95 in protection of self because of the valve preventing them from becoming unsealed during peak outflow. And of course they are much more comfortable to wear for long periods and during heavy work. I just wish the US government would go all in on production of real, effective, fit N95 masks and distribute them to everyone.
- yyyk 6y ago
  The authors themselves point out the valved N95 masks might be worse than what the raw results show: "Furthermore, the performance of the valved N95 mask is likely affected by the exhalation valve, which opens for strong outwards airflow. While the valve does not compromise the protection of the wearer, it can decrease protection of persons surrounding the wearer." [emph. mine]
  - makomk 6y ago
    I'm pretty sure the difference they're referring to is already there in the raw results - remember, they're measuring how well the masks protect others against the wearer by filtering out expelled moisture droplets, and the results show that valved N95 masks are worse than non-valved (though about as good as the very best of the cotton masks).
    - yyyk 6y ago
      I doubt the results completely account for the airflow effect, and perhaps the researchers were careful enough to note this. After all, they merely tested one infected person speaking at whatever level is normal for that person at that stage of the disease. It's quite possible that the typical carrier has stronger flow. Besides, sometimes people yell - quite a few people have reason to be on edge these days.
      - 6y ago
jjoonathan 6y ago
Yesterday I walked through a cloud of gnats with my mask on. I breathed in. No gnats got through. That's something!
known 6y ago
Check https://masks4all.co https://masks4all.co
glofish 6y ago
The damages and side effects of masks are consistently and systematically downplayed. Benefits are vanishing if exist at all. The group think is such that you will never see any of these mentioned in the media. Here is a study that shows that cotton masks increase(!) the incidence of flu like diseases: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ And here is a study that warns that wearing masks leads to cardiac damage: https://link.springer.com/article/10.1007/s00392-020-01704-y https://link.springer.com/article/10.1007/s00392-020-01704-y
- Nav_Panel 6y ago
  From first study: "The null hypothesis is that there is no difference between medical masks and cloth masks. ... The control arm was ‘standard practice’, which comprised mask use in a high proportion of participants [NOT "mask free"]." -- this means "increase relative to surgical masks", not relative to no mask. Second study is only N95s. Just don't wear an N95 if you need more air for aerobic capacity. The OP study shows that they're not _that_ much better than surgical masks anyway. But hey believe what you want to believe.
  - glofish 6y ago
    not sure what your are getting at with the null hypothesis. Look at the results. Mandatory cloth masks were associated with 3 times as many ILIs (Influenza Like Illnesses). So it is not some tiny statistical variation. It is a huge effect size. As for the second study, it concludes:"The observed mechanisms may lead to more severe symptoms in individuals with impaired capacity for myocardial compensation." I am talking about how the all sources of information systematically downplay the negative effects and serious side effects of masks. Masks do have side effects. The relentless propaganda tells you that is a "mere inconvenience".
    - Nav_Panel 6y ago
      > 3 times as many ILIs Compared to surgical masks. There was no study of unmasked people. I expect it would be 10x. > The observed mechanisms may lead to more severe symptoms in individuals with impaired capacity for myocardial compensation. The study was only on N95 masks! Most people are wearing surgical or cloth, it's irrelevant. > I am talking about how the all sources of information systematically downplay the negative effects and serious side effects of masks. There appear to be very few, similar to how all sources downplay the negative effects of walking on the sidewalk vs walking in the road. I would be a lot more sympathetic if you targeted your ire at "washing down surfaces", because that seems irrelevant with respect to spread. But masks work, and that's the long and short of it.
jschwartzi 6y ago
I’d be interested in seeing them test the CDC mask pattern for bandanas because that pattern has you make like 9 layers. I slip a piece of shop towel in the folds and put pipe cleaners at the nose bridge.
rbritton 6y ago
Have there been any studies that factor in the repeated reuse of the same masks?

107 points by pat2man 6y ago

deleted 6y ago

[deleted]

It's kinda sad how the U.S. perceivedly went from conquering space and innovating to getting stuck having basic discussions about climate change, flat earth, vaccination and the effectiveness of face masks. I know it's all on the surface, a vocal minority if you will,and that great science continues to exist and innovation is ever so strong but boy would scientists from the 50s be disappointed if they were to look at the public discourse these days.

Waterfall 6y ago
Do you really think everyone in the 50s was in stem, supported the space program, and innvoates? It's always a minority. They were bombing soldiers, us soldiers with nuclear weapons saying it was harmless to see the effects. Is it sad we don't do that anymore? Just because you watch TV and have a bad Facebook feed doesn't make it America
- adrianN 6y ago
  I think it's important which minority is seen as role model. The cultural narrative is was shapes the next decades.
082349872349872 6y ago
Many US scientists from the 50s hadn't been educated in-country, as they were refugees from the Old World.
Broken_Hippo 6y ago
There has been a strong anti-science component in the US for literally centuries. These advances have been despite the sentiment. In addition, it isn't like other countries weren't going to space or weren't working on it (just like now). Tech has been mirrored elsewhere for a long time, but an American education might lead you to believe differently (I know mine didn't really mention that things like cars were being developed elsewhere - they just mention the first American to make things). If you want a fine example of this, look at the push against modern medicine. Folks were eshewing "European-style medicine" for quite some time. The US Took a really, really long time to eliminate lead from paint and gasoline, comparatively, even though we knew about the harm. We knew things about climate change before WWII, and the denial then was pretty strong. People were scoffing about Earth Day when I was a child - I'm 42 now. Anti-maskers were about in the 1910's with the Spanish flu. The anti-vax movement has been around since.. well, around the time we started to have vaccines. Yes, folks lined up for them, but not everyone. It is a whole heck of a lot easier to be vocal about it now, though, and easier to reach others to try to convince them.
- fpgaminer 6y ago
  Yeah, it's interesting, even the comment you're replying to betrays the duality. 50 years ago the U.S. put a man on the moon, following the coattails of the civil rights movement, meanwhile suffering through one of the most corrupt presidencies, a resurgence of white supremacy that would echo for decades to come, and the beginning of an ignorant war that would destroy the lives of many tens of millions of Americans (the war on drugs). And here we are, today, with an American company SpaceX yet again redefining humanity's reach and we are again suffering through easily the most corrupt presidency to date, white supremacy, and ignorance that is destroying American lives. I think like many it's hard not to look at America today and worry that things are worse than they've ever been. But I think in many ways you're right; America has always been like this. A violent cocktail of the best and worst of humanity, shaken, not stirred.
mattmanser 6y ago
I was rewatching Stranger Things last night and Hopper made a comment about how a missing child brings out the crazies (his words, for those somehow not in the know, it's a show set in the 80s, no internet, no mobile phones). I'm starting to suspect that the media, police, government in all its forms, just used to filter them all out. File their reports and letters in the wastebin. I do wonder whether we've now just given those people an ability to talk to the whole world via Twitter/Facebook/etc., who aren't filtering them out. So perhaps the narrative was always there, but pre-internet was easily filtered.
- codingdave 6y ago
  This is correct - I remember people had serious concerns about it in the early 90s when the web first started growing. It gave a vehicle for "the crazies" to find each other, talk to each other, and strengthen their views by validating each other. In many cases, this is a good thing as it allows a healthy diversity to grow in our society. But it is a double-edged sword. While it does help people find their tribe, it also creates unhealthy echo chambers.
- brianwawok 6y ago
  They would both filter out the crazies and the Whistleblowers. Bummer we can’t just get the actually useful ones.

pat2man 6y ago

The market for face masks is probably enormous right now but the information out there on which ones to buy is anemic. I assumed this was because masks were such a commodity that it didn't really matter which ones you bought, but this article shows otherwise. Even just among the cotton ones there is quite a difference.

techsupporter 6y ago
I think the broader point is one that still stands: wearing literally anything over your nose and mouth is shown, by this study, to cut droplet by at least 50%. Even the cotton varieties cut it from 70% to 90%. So...people need to just slap something over their two air exchanging orifices on their faces before leaving the house and contribute to the our greater health. You're right about the differences in effectiveness but 70% is still pretty good as long as many people are wearing something and not exposing their noses or wrapping the mask lovingly around their chins.
- Izkata 6y ago
  > wearing literally anything Well, no: the fleece mask broke larger droplets into many smaller ones, resulting in an increase of 10% in the number of droplets compared to the no-mask baseline. Being smaller droplets, they would also hang in the air longer.
  - PierceJoy 6y ago
    Potentially a good thing to keep in mind for the upcoming ski season if people think their fleece face coverings will be effective.
- Kiro 6y ago
  You touch your face more when adjusting the mask so if it's not efficient enough it may be a net negative. Edit: This is one of the main reason the Scandinavian countries recommend against _all_ mask use (including N95) so not sure why I'm getting downvoted for merely saying an inefficient mask could have that problem.

082349872349872 6y ago

The low-tech way I've seen (but not cross-calibrated), thanks to a pair of argie firemen: use an aerosol spray can, eg hairspray, to see what makes it through the mask candidate.

anonytrary 6y ago

I have an even better way, albeit a bit dirty. Take a vape pen and simply put your mask on before exhaling; "eyeball" the size and trajectories of the exhaled vapor, select the mask that wins, and call it a day.

bjackman 6y ago
I don't think there's any reason to assume vapour from a pen resembles the droplets in your breath. In fact, that one of them is visible and the other is not should suggest that they might behave very differently.
- anonytrary 6y ago
  Mask hole size >> size of o2, n2, co2, and pretty much any aromatic molecule, so I doubt it.

nabla9 6y ago

The number of droplets is just one variable. Slowing down their speed is another. Since droplets are heavy and fall down fast that dry aresols, just having transparent face shield might give protection to others.

carbocation 6y ago

Somewhat off topic, but I think that the figure labeling in this article is disappointing. In figure 2, the masks are numbered but not named. In figure 3, the masks are named but not numbered. So, I can't (personally) tell which mask from figure 1 performed well and which mask performed poorly.

Merrill 6y ago
Table 1 gives the relation between mask names and numbers. Having to use the table to relate the pictures to the results does seem very poor.
- carbocation 6y ago
  Thanks - I had actually missed that on my skim-through.

mhb 6y ago

Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7185834/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7185834/

superkuh 6y ago

Nice to see some empirical validation of valved N95 masks still being better than the vast majority of other "masks" when it comes to protecting other people. And of course valved N95 masks are the gold standard for cheap masks (not full organic vapor gas masks, etc) even outperforming non-valved N95 in protection of self because of the valve preventing them from becoming unsealed during peak outflow. And of course they are much more comfortable to wear for long periods and during heavy work. I just wish the US government would go all in on production of real, effective, fit N95 masks and distribute them to everyone.

yyyk 6y ago
The authors themselves point out the valved N95 masks might be worse than what the raw results show: "Furthermore, the performance of the valved N95 mask is likely affected by the exhalation valve, which opens for strong outwards airflow. While the valve does not compromise the protection of the wearer, it can decrease protection of persons surrounding the wearer." [emph. mine]
- makomk 6y ago
  I'm pretty sure the difference they're referring to is already there in the raw results - remember, they're measuring how well the masks protect others against the wearer by filtering out expelled moisture droplets, and the results show that valved N95 masks are worse than non-valved (though about as good as the very best of the cotton masks).
  - yyyk 6y ago
    I doubt the results completely account for the airflow effect, and perhaps the researchers were careful enough to note this. After all, they merely tested one infected person speaking at whatever level is normal for that person at that stage of the disease. It's quite possible that the typical carrier has stronger flow. Besides, sometimes people yell - quite a few people have reason to be on edge these days.
    - 6y ago

jjoonathan 6y ago

Yesterday I walked through a cloud of gnats with my mask on. I breathed in. No gnats got through. That's something!

known 6y ago

Check https://masks4all.co https://masks4all.co

glofish 6y ago

The damages and side effects of masks are consistently and systematically downplayed. Benefits are vanishing if exist at all. The group think is such that you will never see any of these mentioned in the media. Here is a study that shows that cotton masks increase(!) the incidence of flu like diseases: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4420971/ And here is a study that warns that wearing masks leads to cardiac damage: https://link.springer.com/article/10.1007/s00392-020-01704-y https://link.springer.com/article/10.1007/s00392-020-01704-y

Nav_Panel 6y ago
From first study: "The null hypothesis is that there is no difference between medical masks and cloth masks. ... The control arm was ‘standard practice’, which comprised mask use in a high proportion of participants [NOT "mask free"]." -- this means "increase relative to surgical masks", not relative to no mask. Second study is only N95s. Just don't wear an N95 if you need more air for aerobic capacity. The OP study shows that they're not _that_ much better than surgical masks anyway. But hey believe what you want to believe.
- glofish 6y ago
  not sure what your are getting at with the null hypothesis. Look at the results. Mandatory cloth masks were associated with 3 times as many ILIs (Influenza Like Illnesses). So it is not some tiny statistical variation. It is a huge effect size. As for the second study, it concludes:"The observed mechanisms may lead to more severe symptoms in individuals with impaired capacity for myocardial compensation." I am talking about how the all sources of information systematically downplay the negative effects and serious side effects of masks. Masks do have side effects. The relentless propaganda tells you that is a "mere inconvenience".
  - Nav_Panel 6y ago
    > 3 times as many ILIs Compared to surgical masks. There was no study of unmasked people. I expect it would be 10x. > The observed mechanisms may lead to more severe symptoms in individuals with impaired capacity for myocardial compensation. The study was only on N95 masks! Most people are wearing surgical or cloth, it's irrelevant. > I am talking about how the all sources of information systematically downplay the negative effects and serious side effects of masks. There appear to be very few, similar to how all sources downplay the negative effects of walking on the sidewalk vs walking in the road. I would be a lot more sympathetic if you targeted your ire at "washing down surfaces", because that seems irrelevant with respect to spread. But masks work, and that's the long and short of it.

jschwartzi 6y ago

I’d be interested in seeing them test the CDC mask pattern for bandanas because that pattern has you make like 9 layers. I slip a piece of shop towel in the folds and put pipe cleaners at the nose bridge.

rbritton 6y ago

Have there been any studies that factor in the repeated reuse of the same masks?