Low-cost measurement of facemask efficacy for filtering expelled droplets • Hacker News Board

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#51

Post by jamesadney » Sun, Aug 09, 2020, 4:06 PM UTC

glofish wrote: post #43

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/ And here is a study that warns that wearing masks leads to car…

This is a bad faith post intentionally spreading misinformation.

Ignoring the quality of these studies, the first concluded that cloth masks were less effective than medical masks, not that the are worse than no mask. It also evaluated and discussed the use of cloth masks to protect health care workers, not to slow the spread of sars-cov-2 via respiratory droplets.

The second, tiny, study says nothing about damage. Their results suggested that surgical masks reduce cardiopulmonary function slightly with surgical masks and a little more with N95 masks.

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#52

Post by Kiro » Sun, Aug 09, 2020, 4:13 PM UTC

dragontamer wrote: post #48

Kiro wrote: post #44

Earlier quoted context omitted.

Yes, of course but that's the point. That people are unable follow correct mask usage and get sloppy, especially over time.

But why do you think that? The more you practice something, the better you get at it. Assuming people to be 100% noobs at masks for months is a bit pessimistic. It's easier today to use hand sanitizer with masks than months ago. In my experience anyway.

Because it's what the state epidemiologists of the Nordic countries are saying, and why they recommend against mask usage. I'm all for masks btw. All I said was that inefficient masks could be counterproductive due to that reason but apparently even that innocent suggestion is heresy here.

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#53

Post by yyyk » Sun, Aug 09, 2020, 4:33 PM UTC

superkuh wrote: post #34

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 t…

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]

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#54

Post by makomk » Sun, Aug 09, 2020, 4:44 PM UTC

yyyk wrote: post #53

superkuh wrote: post #34

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 t…

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]

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).

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#55

Post by mdorazio » Sun, Aug 09, 2020, 4:46 PM UTC

Kiro wrote: post #16

techsupporter wrote: post #8

Earlier quoted context omitted.

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 effectiven…

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.

You're getting downvoted because you provided zero evidence to backup a claim that seems pretty absurd. Touching your mask to adjust it is not the same as touching your nose, mouth, or eyes directly. Pretty much every reputable recommendation says to wash your hands after removing your mask, which avoids the contamination problem pretty well.

And to your point on Scandinavian countries, where are you getting that information? Here's Norway mandating that travelers from "red" countries wear a face mask until they get home [1] and planning to backpedal on their lax mask policies [2]. Here's Denmark backpedalling on their original mask policy [3]. Here's Iceland updating their policy because they also realized no face masks is a bad idea [4]. Basically, Scandinavian countries now recognize that their original policies were not that great.

[1] https://www.forbes.com/sites/davidnikel/2020/08/07/norway-cl...

[2] https://www.thelocal.no/20200806/norway-expected-to-announce...

[3] https://www.thelocal.dk/20200731/denmark-changes-face-mask-g...

[4] https://icelandmonitor.mbl.is/news/news/2020/07/31/when_to_u...

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#56

Post by glofish » Sun, Aug 09, 2020, 4:52 PM UTC

Nav_Panel wrote: post #45

glofish wrote: post #43

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/ And here is a study that warns that wearing masks leads to car…

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…

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".

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#57

Post by pmachinery » Sun, Aug 09, 2020, 4:53 PM UTC

Kiro wrote: post #52

dragontamer wrote: post #48

Earlier quoted context omitted.

But why do you think that? The more you practice something, the better you get at it. Assuming people to be 100% noobs at masks for months is a bit pessimistic. It's easier today to use hand sanitizer with masks than months ago. In my experience anyway.

Because it's what the state epidemiologists of the Nordic countries are saying, and why they recommend against mask usage. I'm all for masks btw. All I said was that inefficient masks could be counterproductive due to that reason but apparently even that innocent suggestion is heresy here.

It's not heresy, it's just a banality that has been stated countless times before.

Not washing your hands properly can be counterproductive. Not being socially distant enough can be counterproductive.

If you're not even arguing against masks, what is your point?

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#58

Post by glofish » Sun, Aug 09, 2020, 4:53 PM UTC

jamesadney wrote: post #51

glofish wrote: post #43

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/ And here is a study that warns that wearing masks leads to car…

This is a bad faith post intentionally spreading misinformation. Ignoring the quality of these studies, the first concluded that cloth masks were less effective than medical masks, not that the are worse than no mask. It also evaluated and discussed the use of cloth masks to protect health care workers, not to slow the spread of sars-cov-2 via respiratory droplets. The second, tiny, study says nothing about damage. T…

That is not what the paper found, all you need is to read the abstract:

"Cloth masks also had significantly higher rates of ILI compared with the control arm"

As for the second paper here is the summarry:

"The increased breathing resistance is especially problematic for patients with chronic obstructive pulmonary diseases. Patients with diffusion disorders have reduced capacity to compensate due to the reduced tidal volume. Another example of a population at risk is patients with heart failure. The observed mechanisms may lead to more severe symptoms in individuals with impaired capacity for myocardial compensation."

All I am pointing out is that masks are likely to have serious side effects, all which are completely disregarded and downplayed.

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#59

Post by yyyk » Sun, Aug 09, 2020, 4:56 PM UTC

makomk wrote: post #54

yyyk wrote: post #53

Earlier quoted context omitted.

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]

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).

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.

Re: Low-cost measurement of facemask efficacy for filtering expelled droplets

#60

Post by zucker42 » Sun, Aug 09, 2020, 4:59 PM UTC

glofish wrote: post #58

jamesadney wrote: post #51

Earlier quoted context omitted.

This is a bad faith post intentionally spreading misinformation. Ignoring the quality of these studies, the first concluded that cloth masks were less effective than medical masks, not that the are worse than no mask. It also evaluated and discussed the use of cloth masks to protect health care workers, not to slow the spread of sars-cov-2 via respiratory droplets. The second, tiny, study says nothing about damage. T…

That is not what the paper found, all you need is to read the abstract: " Cloth masks also had significantly higher rates of ILI compared with the control arm " As for the second paper here is the summarry: " The increased breathing resistance is especially problematic for patients with chronic obstructive pulmonary diseases. Patients with diffusion disorders have reduced capacity to compensate due to the reduced tid…

The control arm included mask usage.