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Face masks effectively limit the probability of SARS-CoV-2 transmission

science.sciencemag.org

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Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#61

Post by brobdingnagians »

takeda wrote: post #47
brobdingnagians wrote: post #22

This isn't a study; it is a mathematical model [1]. > Here, we develop a quantitative model of airborne virus exposure that can explain these contrasting results and provide a basis for quantifying the efficacy of face masks. We show that mask efficacy strongly depends on airborne virus abundance. Based on direct measurements of SARS-CoV-2 in air samples and population-level infection probabilities, we find that the…

The study about mask being ineffective is about cloth mask. That's why the hospital masks are no longer made of cloth.

That is true; but a large number of people are walking around with cloth masks believing that they are helpful, while that study has shown them to potentially increase risk.

It did show "Penetration of cloth masks by particles was almost 97% and medical masks 44%." So that was a positive for medical masks. Though some of the other studies address how those need to be used properly and not re-used.

The main point is that, in general, media has not done a good job of transmitting studies on risk reduction; they've mainly done propaganda, which can do more harm by promoting things like cloth masks and not informing people about proper use of medical masks.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#62

Post by petertodd »

matz1 wrote: post #54
sschueller wrote: post #17

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

The problem is wearing mask is annoying and uncomfortable. If I have to choose, I'll choose the increased risk of covid all the time rather than wearing mask.

A big part of why they are annoying and uncomfortable is the lack of one-way valves to make it easier to breath in them. In industry, when you actually need to wear a mask/respirator, they almost always have valves.

Unfortunately, we got stuck on the "wear masks to protect others" narrative, and people who actually were at risk were prevented from wearing much more effective, much more comfortable, masks that would actually work well at protecting them. Eg here in Canada, it's illegal to wear a mask/respirator with a valve on a plane.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#63

Post by blumomo »

kickopotomus wrote: post #32
bitcurious wrote: post #24

Earlier quoted context omitted.

I’m not sure there was any popular doubt over the efficacy of N95 masks. The problem was rather getting one - marketplaces like Amazon restricted access to masks if you weren’t affiliated with a hospital. So you were left with sketchy deals and weird vendor sites. I suspect Amazon killed quite a few people over the last year by restricting access - supply scaled pretty quickly.

Unfortunately, a few of my friends fell victim to the Qanon conspiracy bandwagon and the fact that mask pore size is wider than the virus was heavily circulated as a reason for mask ineffectiveness.

Everyone is having assumptions about these observations. The conclusions might not be always right, but at least the observation is real. And when you observe that mask mandating states don’t do significantly better than mask-free states, then a curious mind rightfully starts pondering. No need to unterstand conspiracy theories (a difficult topic) to understand that science isn’t getting it right yet.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#64

Post by cimi_ »

takeda wrote: post #34
splitrocket wrote: post #5

Earlier quoted context omitted.

Virus particles do not travel naked in the air, instead they are colloidally suspended in liquid, both droplets and aerosols. So, if your filter catches the droplets and aerosols, which are much larger in size than the actual virus, the filter works.

Realization that somebody's droplets are getting into your mouth and nose makes one want to wear mask even after pandemic is over :)

You're of course free to do whatever you think makes sense, but please don't expect other people to follow. The world is full of risks, but everything is a tradeoff - it's really bad if we start thinking random people are a danger to us.

And for what it's worth, I'm not anti-mask in the context of the pandemic - I've been wearing masks indoors since the whole thing started and I'll continue to do this until most people around me are vaccinated, for their sake.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#65

Post by omegaworks »

tgsovlerkhgsel wrote: post #39

This entire study seems to be centered around a theoretical, mathematical model, and I didn't see any attempt to actually validate that model. Basically, the authors seem to assume that the virus behaves according to their formulas, and show that under their assumptions, face masks work, but don't actually prove that their assumptions match reality - or did I miss something?

It invites rigor in studying mask efficacy. Some studies out there show inconclusive results of mask usage, and this article helps give us an explanation as to why we might be seeing that. The model shows that in an extremely virus-rich environment masking can be rendered ineffective, but in virus-poor environments, even surgical masks decrease the probability of infection.

Researchers need to measure concentration of virus in the environment as well as mask usage to show the efficacy of masks in real world situations.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#66

Post by abfan1127 »

splitrocket wrote: post #5
tryonenow wrote: post #2

>Surgical masks with particle collection efficiencies around ~50% cannot prevent the release of millions of particles per person and their inhalation by others (green dots in Fig. 1, B and D). In other words, the human-emitted respiratory particle number is so high that we cannot avoid inhaling particles generated by another person even when wearing a surgical mask So the entire premise of the modeling in the paper r…

Virus particles do not travel naked in the air, instead they are colloidally suspended in liquid, both droplets and aerosols. So, if your filter catches the droplets and aerosols, which are much larger in size than the actual virus, the filter works.

assuming: 1) 100% capture of air flow 2) no fatigue (ie capture is same at t=0, and t=later)

anyone with glasses will tell you 1 isn't a very good assumption. As masks saturate in moisture, back pressure causes (1) to be more false.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#67

Post by matz1 »

petertodd wrote: post #62
matz1 wrote: post #54

Earlier quoted context omitted.

The problem is wearing mask is annoying and uncomfortable. If I have to choose, I'll choose the increased risk of covid all the time rather than wearing mask.

A big part of why they are annoying and uncomfortable is the lack of one-way valves to make it easier to breath in them. In industry, when you actually need to wear a mask/respirator, they almost always have valves. Unfortunately, we got stuck on the "wear masks to protect others" narrative, and people who actually were at risk were prevented from wearing much more effective, much more comfortable, masks that would a…

Not only that, there is one more thing to carry when you go out and impairment of social interaction because of lack of facial expression.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#68

Post by bsder »

Laforet wrote: post #55
bitcurious wrote: post #24

Earlier quoted context omitted.

I’m not sure there was any popular doubt over the efficacy of N95 masks. The problem was rather getting one - marketplaces like Amazon restricted access to masks if you weren’t affiliated with a hospital. So you were left with sketchy deals and weird vendor sites. I suspect Amazon killed quite a few people over the last year by restricting access - supply scaled pretty quickly.

According to the data presented, surgical masks are still highly effective even after converting the scales to linear. Add social distancing on top, it is almost as good as N95. And I very much doubt that N95 masks are effectively utilized by the general public considering how many poorly fitted masks I have seen over the past year. Before the pandemic there had been several studies looking at the efficacy of N95 vs.…

> And I very much doubt that N95 masks are effectively utilized by the general public considering how many poorly fitted masks I have seen over the past year.

I agree. When people can't even wear surgical masks properly, there's no hope with an N95.

> Most of them never got anywhere because it was soon realized that even doctors and nurses cannot be trusted to wear and change masks properly during the daily routine. Let's hope things have improved by now.

At the very least, everybody is washing their hands. Before Covid, you couldn't even get all the doctors to do something even that simple.

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#69

Post by slashdot2008 »

petertodd wrote: post #62
matz1 wrote: post #54

Earlier quoted context omitted.

The problem is wearing mask is annoying and uncomfortable. If I have to choose, I'll choose the increased risk of covid all the time rather than wearing mask.

A big part of why they are annoying and uncomfortable is the lack of one-way valves to make it easier to breath in them. In industry, when you actually need to wear a mask/respirator, they almost always have valves. Unfortunately, we got stuck on the "wear masks to protect others" narrative, and people who actually were at risk were prevented from wearing much more effective, much more comfortable, masks that would a…

I don't think it is an unfortunate narrative. two people wearing masks without valves is twice the reduction in likelihood that either one gives the other covid. If someone does have covid the mask without the valve will greatly reduce the concentration of virus particles in the air around them. I think that is working as intended!

Re: Face masks effectively limit the probability of SARS-CoV-2 transmission

#70

Post by goatcode »

sschueller wrote: post #17

N95/FFP2 seem to be very effective. I wish the media and government would have spent more time in educating people in things like how N95 masks work and that it isn't like a coffee filter. Even thought the pores are larger than a virus the masks are statically charged causes smaller things to get trapped. Many people don't know this but probably had an interaction with static electricity sometime in school and would…

The only time "N95" was uttered was last year, when we were being told: 1. Masks aren't needed; 2. Don't buy masks, healthcare workers need them.

It's unfortunate that we didn't go back to talking about proper masks before people started knitting them and making them out of rags and beads. One wonders what difference it might have made.

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