6 ms·

MIT study finds indoor mask wearing much more effective than social distancing

63 points by antattack 5y ago

excerionsforte 5y ago
I mean respiratory virus meet respiratory system. You cover your respiratory system and you are most of the way there for protecting yourself. Social distancing indoors wouldn't be effective without ventilation as you'd be breathing in the same air that others are exhaling. Touching on the other hand, it is very effective for. You still wouldn't want to be in a room for extended time if someone is exhaling the virus as the mask can only do so much. Just more evidence for what I think is obvious.
- dathinab 5y ago
  The mask also "slows down" the exhaust making airosoles which escaped the mask of the infected person "be" more around that person, instead of further spread. Which combined with e.g. a air filter system which pulls out air (instead of pushing it in) can reduce the risk by quite a bit (especially if the system is installed at the ceiling). Or so I have heard. Which makes me wonder if you could "invert" and AC to act as such system in a improvising manner. I think there are also AC, which do both: Pushing in fresh air and pulling out old air. Which probably have the best chances to reduce infection, especially if combined with wearing at least some kind of mask.
briefcomment 5y ago
"By assuming that the respiratory droplets are mixed uniformly through an indoor space..." ... Is this a reasonable starting point? Social distancing assumes the distribution is not uniform. You would think the researchers would try measuring the distribution first instead of just assuming that a priori. Edit: Haha, I'm struggling to understand the point of this study when they state something like this: "These models are all based on the premise that the space of interest is well mixed; thus, the pathogen is distributed uniformly throughout. In such well-mixed spaces, one is no safer from airborne pathogens at 60 ft than 6 ft."
- dathinab 5y ago
  No not at all. Airflow in buildings is a complex topics and needs to be modeled with complex computer simulations to get right as "intuitive" assumptions can sometimes be very far of the reality. Any single source of heat, like heaters, laptops or even your body heat is influencing this. There are companies which do such analysis for hospitals to make sure/reduce the risk that Covid from Covid patients infect non-Covid patients over air flow. (Best would be an airlock between areas, but lets be realistic especially when they get many Covid patients this is often not possible). Either way it's completely unrealistic assumption. Still from all what I know about air (subtile) flow (which is not much) the end conclusion of: "wearing mask indoors is quite effective, maybe more then social distancing". Might still be true, assuming you don't strictly social distance etc.. Because not being ever in the same apartment as an affected person is definitively better then being there with a mask ;=). A example of how waring a mask indoors might unexpectedly help is that you body heat creates a minimal updraft, minimal but then the virus water droplets are also supper light wight. So if you combine a air conditioning/filter system which pulls out air (not uncommon for hospitals) with a mask and that effect the mask will cause the remaining airosoles to be "closer" to you as they where at least slowed down even if they escaped and the minimal updraft + vacuuming air filter system will with that have a higher chance to "pull out" the virus before any one can get affected by it. Or at least that is what I heard from some people of which I forgot the name of which do indoor air flow simulations.
- prvc 5y ago
  Borders on fraud, when such a strong unproven assumption gets transformed into a "guideline", which will then be disseminated and reported to a wider audience which isn't inclined to look into the details.
- upofadown 5y ago
  In an enclosed space mixing will eventually occur. The question is; how fast? So if social distancing initially works then there would come a time where it does not. If the mixing is fast enough in practice then this model might not be effected all that much if it predicts significant risk later.
barathr 5y ago
I hope we can get to a place by the Fall that everyone leaves windows open in public buildings, workplaces, etc. if they can be opened. It's the simplest mitigation strategy. The next easiest is changing the HVAC system to pull outdoor air in rather than recirculating the air, and putting in a higher MERV filter. Mask wearing is good too, but should be seen as a bonus on top of these simpler strategies. Less surface cleaning and more focus on air.
- woofie11 5y ago
  Mask wearing is incredibly effective with N95-equivalent masks, which are now easily and plentifully available. If everyone wore masks with proper filters, we might be done by now. The world seems too dumb to notice the difference between a piece of cloth and a proper filter. If everyone wears N95 masks, the virus basically doesn't seem to spread.
  - gfodor 5y ago
    Agree of all the stupidity in this pandemic, the false equivalence implied by leadership between n95s and cloth masks has probably killed the most people counterfactually. Particularly if you assume it has led to a false sense of safety by cloth-wearers, leading them to take risky behavior like going indoors they would have avoided otherwise if their cheap masks were explained to be insufficient protection.
    - metiscus 5y ago
      I tend to agree with you on this. I've got some anecdata and commentary. So obviously I'm not the CDC or a doctor so don't decide anything based on my story here. My wife works in the hospital and employees are only given one mask a month or so and must use the hospital provided equipment. For staff that are not in the covid units, incidents of transmission and overall infection rates have been very low. For those in the covid units themselves, the infection rates are 60-70%. The PPE situation is still quite poor, gowns and face shields are being reused where in ordinary times they would be disposable. For ordinary people without regular contact with the infected and who take reasonable precautions (modeled in my anecdata by the staff outside the covid units) I believe that the masks combined with frequent hand washing are probably pretty effective. If you're in suboptimal circumstances and in constant contact with the infected I don't know. It's hard to tell with all of the PPE reuse. The story being told is that the cloth masks reduce spread from you to others but do not overtly protect you. I can see circumstances where improper doffing techniques could cause these to be counterproductive but overall I tend to believe this. Properly fitted N95 masks have similar protection of others but also protect you from some, but probably not all exposures.
logicslave 5y ago
"Study finds not driving a car much safer than driving a car", lets all stop driving and walk everywhere
- Barrin92 5y ago
  well that's unironically a good idea and it's why many of the most livable cities on earth aren't designed around cars, let's do it like Pontevedra, reinvigorated small business, improved air quality, noise pollution and people's level of physical activity: https://www.theguardian.com/cities/2018/sep/18/paradise-life-spanish-city-banned-cars-pontevedra https://www.theguardian.com/cities/2018/sep/18/paradise-life...
- chriswphoto 5y ago
  Yes! Best idea on here. Cars do so much damage to humans, cities and the planet.
akudha 5y ago
Social distancing is good, even if it doesn't help with covid. In the past year, I've seen people respect personal space a bit more. For example, while shopping. That is a positive thing in my book.
cheald 5y ago
This is a mathematical model, not a study of empirical data. It's worth distinguishing, because models are only as good as their assumptions. The model presumes a "filtration constant" for masks, which only apply for pressure-sealed masks, like properly-fitted N95s. Simple face coverings don't do much to protect you against aerosols, for the same reason that they don't do much to mitigate the effects of attempting to breathe in a smoke-filled room - the airflow is just redirected through the sides and top of the mask, rather than being filtered. So, while the results may have some value for N95s, I seriously question their value for "masks" as they are currently colloquially understood.
- toomim 5y ago
  A filtration constant can apply to poorly-fitted masks, too. They just have a smaller constant. The filtration constant for a well-sealed N95 can be 99.99%. The filtration constant for a thin cotton "face covering" can be 20%. The point isn't that the model doesn't apply to poor masks -- it's that they have poor constants. We will do much better to include them in the model, and then mathematically predict how important it is to improve your filtration constant, than to say "those masks don't apply" and throw up our hands at quantifying the improvement that could be gained by better masks.
exabrial 5y ago
These "studies" are stupid. Airflow is the [likely only] thing that matters. Social distancing in a 0 airflow environment isn't going to work, as droplets stay suspended. Masks prevent large droplet spread, but aren't fully effective (which is well known). What is effective is physics. It's impossible for a droplets to spread upwind, and often downwind as well, since they don't hang around in suspension. Get airflow certifications/requirements updated would not only help small businesses recover quicker but also pay dividends during normal flu season, let alone a pandemic.
- solarengineer 5y ago
  This is the first that I’m reading about “airflow certifications/requirements”. A brief search led me to this article explaining the concept of HVAC balancing. [0] [0] https://www.primexvents.com/certification-matters-balancing-hvac/ https://www.primexvents.com/certification-matters-balancing-...
29athrowaway 5y ago
You cannot get an infectious disease from someone who is not there. Stay home if you can.
mattkrause 5y ago
Actual article title: “A guideline to limit indoor airborne transmission of COVID-19” The actual article doesn’t seem to have the spin described in the title.
deleted 5y ago
[deleted]
chmod600 5y ago
It seems we are increasingly leaving the scientific method out of science. The scientific method is the most powerful tool we have to determine causation. It's also very strict, which means that it's limited in applicability. It's strict because you have to intervene in the real world after forming a hypothesis about what change might be caused by that intervention. The experiment should be constructed to try to refute the hypothesis. Increasingly, what I'm seeing is observational "science", where you keep forming hypothesis until you find one that fits the data you have. Another thing I see, which this MIT study appears to be, is where the scientists completely make up a fictional world (called a model), and intervene in that fictional world. (Note: models are more likely to work when they aren't completely made up by scientists. For instance, mouse models are very important to life sciences. But the reason they are useful is because scientists can't make up a complete fiction to support their preferred conclusion -- they still have to face the realities of mammals in all their complexity.) I wish we could have a different word for this, so that people can't use the vaneer of science to add authority to something as though it were a law of physics.

63 points by antattack 5y ago

I mean respiratory virus meet respiratory system. You cover your respiratory system and you are most of the way there for protecting yourself. Social distancing indoors wouldn't be effective without ventilation as you'd be breathing in the same air that others are exhaling. Touching on the other hand, it is very effective for. You still wouldn't want to be in a room for extended time if someone is exhaling the virus as the mask can only do so much. Just more evidence for what I think is obvious.

dathinab 5y ago
The mask also "slows down" the exhaust making airosoles which escaped the mask of the infected person "be" more around that person, instead of further spread. Which combined with e.g. a air filter system which pulls out air (instead of pushing it in) can reduce the risk by quite a bit (especially if the system is installed at the ceiling). Or so I have heard. Which makes me wonder if you could "invert" and AC to act as such system in a improvising manner. I think there are also AC, which do both: Pushing in fresh air and pulling out old air. Which probably have the best chances to reduce infection, especially if combined with wearing at least some kind of mask.

briefcomment 5y ago

"By assuming that the respiratory droplets are mixed uniformly through an indoor space..." ... Is this a reasonable starting point? Social distancing assumes the distribution is not uniform. You would think the researchers would try measuring the distribution first instead of just assuming that a priori. Edit: Haha, I'm struggling to understand the point of this study when they state something like this: "These models are all based on the premise that the space of interest is well mixed; thus, the pathogen is distributed uniformly throughout. In such well-mixed spaces, one is no safer from airborne pathogens at 60 ft than 6 ft."

dathinab 5y ago
No not at all. Airflow in buildings is a complex topics and needs to be modeled with complex computer simulations to get right as "intuitive" assumptions can sometimes be very far of the reality. Any single source of heat, like heaters, laptops or even your body heat is influencing this. There are companies which do such analysis for hospitals to make sure/reduce the risk that Covid from Covid patients infect non-Covid patients over air flow. (Best would be an airlock between areas, but lets be realistic especially when they get many Covid patients this is often not possible). Either way it's completely unrealistic assumption. Still from all what I know about air (subtile) flow (which is not much) the end conclusion of: "wearing mask indoors is quite effective, maybe more then social distancing". Might still be true, assuming you don't strictly social distance etc.. Because not being ever in the same apartment as an affected person is definitively better then being there with a mask ;=). A example of how waring a mask indoors might unexpectedly help is that you body heat creates a minimal updraft, minimal but then the virus water droplets are also supper light wight. So if you combine a air conditioning/filter system which pulls out air (not uncommon for hospitals) with a mask and that effect the mask will cause the remaining airosoles to be "closer" to you as they where at least slowed down even if they escaped and the minimal updraft + vacuuming air filter system will with that have a higher chance to "pull out" the virus before any one can get affected by it. Or at least that is what I heard from some people of which I forgot the name of which do indoor air flow simulations.
prvc 5y ago
Borders on fraud, when such a strong unproven assumption gets transformed into a "guideline", which will then be disseminated and reported to a wider audience which isn't inclined to look into the details.
upofadown 5y ago
In an enclosed space mixing will eventually occur. The question is; how fast? So if social distancing initially works then there would come a time where it does not. If the mixing is fast enough in practice then this model might not be effected all that much if it predicts significant risk later.

barathr 5y ago

I hope we can get to a place by the Fall that everyone leaves windows open in public buildings, workplaces, etc. if they can be opened. It's the simplest mitigation strategy. The next easiest is changing the HVAC system to pull outdoor air in rather than recirculating the air, and putting in a higher MERV filter. Mask wearing is good too, but should be seen as a bonus on top of these simpler strategies. Less surface cleaning and more focus on air.

woofie11 5y ago
Mask wearing is incredibly effective with N95-equivalent masks, which are now easily and plentifully available. If everyone wore masks with proper filters, we might be done by now. The world seems too dumb to notice the difference between a piece of cloth and a proper filter. If everyone wears N95 masks, the virus basically doesn't seem to spread.
- gfodor 5y ago
  Agree of all the stupidity in this pandemic, the false equivalence implied by leadership between n95s and cloth masks has probably killed the most people counterfactually. Particularly if you assume it has led to a false sense of safety by cloth-wearers, leading them to take risky behavior like going indoors they would have avoided otherwise if their cheap masks were explained to be insufficient protection.
  - metiscus 5y ago
    I tend to agree with you on this. I've got some anecdata and commentary. So obviously I'm not the CDC or a doctor so don't decide anything based on my story here. My wife works in the hospital and employees are only given one mask a month or so and must use the hospital provided equipment. For staff that are not in the covid units, incidents of transmission and overall infection rates have been very low. For those in the covid units themselves, the infection rates are 60-70%. The PPE situation is still quite poor, gowns and face shields are being reused where in ordinary times they would be disposable. For ordinary people without regular contact with the infected and who take reasonable precautions (modeled in my anecdata by the staff outside the covid units) I believe that the masks combined with frequent hand washing are probably pretty effective. If you're in suboptimal circumstances and in constant contact with the infected I don't know. It's hard to tell with all of the PPE reuse. The story being told is that the cloth masks reduce spread from you to others but do not overtly protect you. I can see circumstances where improper doffing techniques could cause these to be counterproductive but overall I tend to believe this. Properly fitted N95 masks have similar protection of others but also protect you from some, but probably not all exposures.

logicslave 5y ago

"Study finds not driving a car much safer than driving a car", lets all stop driving and walk everywhere

Barrin92 5y ago
well that's unironically a good idea and it's why many of the most livable cities on earth aren't designed around cars, let's do it like Pontevedra, reinvigorated small business, improved air quality, noise pollution and people's level of physical activity: https://www.theguardian.com/cities/2018/sep/18/paradise-life-spanish-city-banned-cars-pontevedra https://www.theguardian.com/cities/2018/sep/18/paradise-life...
chriswphoto 5y ago
Yes! Best idea on here. Cars do so much damage to humans, cities and the planet.

akudha 5y ago

Social distancing is good, even if it doesn't help with covid. In the past year, I've seen people respect personal space a bit more. For example, while shopping. That is a positive thing in my book.

cheald 5y ago

This is a mathematical model, not a study of empirical data. It's worth distinguishing, because models are only as good as their assumptions. The model presumes a "filtration constant" for masks, which only apply for pressure-sealed masks, like properly-fitted N95s. Simple face coverings don't do much to protect you against aerosols, for the same reason that they don't do much to mitigate the effects of attempting to breathe in a smoke-filled room - the airflow is just redirected through the sides and top of the mask, rather than being filtered. So, while the results may have some value for N95s, I seriously question their value for "masks" as they are currently colloquially understood.

toomim 5y ago
A filtration constant can apply to poorly-fitted masks, too. They just have a smaller constant. The filtration constant for a well-sealed N95 can be 99.99%. The filtration constant for a thin cotton "face covering" can be 20%. The point isn't that the model doesn't apply to poor masks -- it's that they have poor constants. We will do much better to include them in the model, and then mathematically predict how important it is to improve your filtration constant, than to say "those masks don't apply" and throw up our hands at quantifying the improvement that could be gained by better masks.

exabrial 5y ago

These "studies" are stupid. Airflow is the [likely only] thing that matters. Social distancing in a 0 airflow environment isn't going to work, as droplets stay suspended. Masks prevent large droplet spread, but aren't fully effective (which is well known). What is effective is physics. It's impossible for a droplets to spread upwind, and often downwind as well, since they don't hang around in suspension. Get airflow certifications/requirements updated would not only help small businesses recover quicker but also pay dividends during normal flu season, let alone a pandemic.

solarengineer 5y ago
This is the first that I’m reading about “airflow certifications/requirements”. A brief search led me to this article explaining the concept of HVAC balancing. [0] [0] https://www.primexvents.com/certification-matters-balancing-hvac/ https://www.primexvents.com/certification-matters-balancing-...

29athrowaway 5y ago

You cannot get an infectious disease from someone who is not there. Stay home if you can.

mattkrause 5y ago

Actual article title: “A guideline to limit indoor airborne transmission of COVID-19” The actual article doesn’t seem to have the spin described in the title.

deleted 5y ago

[deleted]

chmod600 5y ago

It seems we are increasingly leaving the scientific method out of science. The scientific method is the most powerful tool we have to determine causation. It's also very strict, which means that it's limited in applicability. It's strict because you have to intervene in the real world after forming a hypothesis about what change might be caused by that intervention. The experiment should be constructed to try to refute the hypothesis. Increasingly, what I'm seeing is observational "science", where you keep forming hypothesis until you find one that fits the data you have. Another thing I see, which this MIT study appears to be, is where the scientists completely make up a fictional world (called a model), and intervene in that fictional world. (Note: models are more likely to work when they aren't completely made up by scientists. For instance, mouse models are very important to life sciences. But the reason they are useful is because scientists can't make up a complete fiction to support their preferred conclusion -- they still have to face the realities of mammals in all their complexity.) I wish we could have a different word for this, so that people can't use the vaneer of science to add authority to something as though it were a law of physics.