Mask effectiveness

[disco stu]

So I've been pondering how effective masks are for a while, especially since having to wear one in a room full of people for 6 hours a day. This is not a conversation about covid, but the science and research around masks.

** I'm very keen for this to not devolve into another argument thread. I'm keen to hear people's thoughts, but not to argue about covid etc**

I'm sure we've all noticed when wearing masks that most of the air is blowing around the sides and out the top. All you have to do is wear glasses to see this in action. I've also noticed when going to sneeze, when you suddenly breath in before the sneeze, when that mask sucks tight onto your mouth that you can't actually breath through it at all. It's just so restrictive to letting air through it.

Being a science guy this got me thinking about their use, and wondering how much research has actually been done into their effectiveness, plus how they actually work given that flow around the sides.

If you ask someone how masks work, "they filter the air, like duh-idiot" is the response. You don't need a PhD to know that for a filter to work you need to seal it into the flow or a fluid will just move around rather than through it. Knowing how hard it is to breath through the material when it's sealed around your mouth, it's obvious that most of the air is moving around the mask rather than through it, just like if the mask was made of something impervious like plastic. But does this actually do anything to stop virus or bacteria? It may, but that is the question and you shouldn't assume.

My main thinking here is something like a classroom full of kids, are they just directing their covid laden breaths onto those behind or beside them if the majority of their breath is unfiltered. Face to face people are obviously well protected.

So, off I go doing some research.

Looking at the standards type testing of masks, they seal it in a tube and pass air through it to measure it's filtering ability. Ok, but what about the air passing around it that we all know is occurring? Surely they don't all assume that the whole breath is filtered

So I go and look at scientific studies of mask effectiveness. There are many anecdotal studies comparing transmission of various illnesses in mask and non mask wearing communities. They are all positive that masks work, but none of them say how they work or address that air that moves around the side or top of the mask. Some of these types of studies or comparisons of mask types highlight that fit of the mask is far and away the most important factor, well ahead of particle size filtration etc etc. They don't address masks that you just can't get to seal like surgical masks, or the home made cloth masks that leave that gaping big hole in the top.

What I was looking for was studies that looked at masks being worn and stopping the nasties getting out. There was less of these compared to other types of studies, but still a reasonable amount to look at. Some looked at water droplets outside of the mask, and others used participants who were sick with the flu and measured viral numbers released. One thing they all had in common was they only looked at these things in front of the mask, nothing in regards to leakage around the mask.

So from my somewhat limited research, it seems that all of the studies around masks either assume people will only ever be facing one another, or make the assumption that all of the breath exhaled is filtered through the mask. I found nothing at all that measured the amount of leakage that occurs with the types of masks that the general public are wearing, or that analysed the amount of viruses released in other directions apart from directly in front.

I found this fairly surprising if I'm honest. Surely I'm not the first to notice the amount of air that doesn't get filtered through the mask, and then questioned whether the masks actually do anything. While those studies that find a difference in mask and non mask wearing communities found they work, that doesn't account for other potential reasons for less spread of viruses in those communities. Correlation is not causation and all that.

I thought I would throw this out there, as I'm sure others on here might either find it interesting, or others might actually have looked into this further and could provide some answers.

Keen to hear people's thoughts, while keeping away from covid itself or arguing about government decisions etc etc

[on_one_wheel]

Masks have proven very effective for a long time, that's why doctors, nurses and dentists use them.

Personally I hate wearing them but I prefer to be seen as a rule abiding citizen rather than a self entitled twat.
I have noticed more and more people not using them in SA.

[mchughcb]

Filtering of a N95 mask which if I remember back to my OH&S days was 0.3micron at 95% efficiency assuming a good seal around the face. Not helpful if you have facial hair. Arguments around the size of the virus compared to the filter size, versus the liquid droplets they adhere to versus the viral load required to catch the disease has so many variables that you will constantly be saying "if", this "if" ad nausem then in a laboratory or operating theatre they may make a difference. However translating that to the real world then the assumptions on the absolute best possible conditions in neither realistic or practical.

So the final say is, wear the mask and use some common sense. It might make SFA difference but at least you won't give the thought police a chance to fine you.

[cz515]

So there are a few things to mention. When we talk about masks it should always be properly fitted, esp around your nose and face...so as alluded to above no facial hair. When properly fitted almost all the air is going through the filter material, and I am not sure which makes of masks you use, all the ones I have seen, let air pass through. I have to wear a mask everyday related to my work (before covid) and I can assure you a good mask you can tell the difference in fitments and use, if fitted properly maskes work to filter the smallest dust or microbial particles as specified.

With regards to covid research, they all say is more about stopping the droplets as that's what got a large viral load, hence even wearing surgical masks is better than nothing.

So then you see people wearing the masks in shops, work places etc such that their nose is uncovered.... the mask is doing Jack all, and it's a tiny bit better than wearing nothing.

[disco stu]

Yeah, this isn't about whether I should wear the mask etc. My interest is in the fact whether they're actually effective in the community, more a scientific discussion.

I personally hate wearing them, but had no complaints putting up with it for 20min at Woolworths etc. It was when I had to wear it for 6hrs at work, trying to talk loudly to a class full of kids, that I really started to hate it. It was in the class that I started to wonder about howv they work, I'd they do, or if there was just a lot of assumptions made that no one had ever questioned.

On one wheel-doctors, dentists, surgeons etc are all facing the patient they're protecting. What I'm asking about is when you're not facing that person, given the amount of air blowing out the rear sides are you spreading the same amount, just in a different direction?

[disco stu]

So there are a few things to mention. When we talk about masks it should always be properly fitted, esp around your nose and face...so as alluded to above no facial hair. When properly fitted almost all the air is going through the filter material, and I am not sure which makes of masks you use, all the ones I have seen, let air pass through. I have to wear a mask everyday related to my work (before covid) and I can assure you a good mask you can tell the difference in fitments and use, if fitted properly maskes work to filter the smallest dust or microbial particles as specified.

With regards to covid research, they all say is more about stopping the droplets as that's what got a large viral load, hence even wearing surgical masks is better than nothing.

So then you see people wearing the masks in shops, work places etc such that their nose is uncovered.... the mask is doing Jack all, and it's a tiny bit better than wearing nothing.

What sort of mask do you wear for work? I'm assuming it's a proper fitted respirator type rather than surgical mask, because there doesn't seem to be anything you can do to get a surgical mask to seal of your face. It is a piece of fabric layed over your face, there is nothing to actually seal.

Seriously, anyone who thinks they can breathe through them try sealing it tight against your mouth and breathing through it.

I understand the water droplets etc, I did mention this in my post. What I'm wondering is do those water droplets actually get trapped when that air blows around the openings in the mask? I'm asking if anyone has quantified this, because I've only seen data from in front of the mask. That screams assumptions during the testing. I'm interested in the mechanism causing them to be trapped if they are, but I don't even know if they're trapped in that unfiltered air yet.

I'm not just assuming at least some of the air blows out the openings, I know it does in the surgical masks everyone is wearing. I seal it against my nose as well as I can and my sunnies are fogging up even on hot days. Puts it's going out the sides

[disco stu]

Maybe I'm not being clear enough. I'm purely talking about surgical or cloth masks here, ones which don't have rubber or similar to seal around the face. The only fitment is that they're laying over your mouth and nose, with a small piece of wire over noise bridge. The most common type seen in the community. Not referring to n95 or similar, what they call respirators in the literature, used where filteting out things is essential to the wearer's safety. I'm well aware that they work well when fitted properly

I'm also not questioning if there is leakage and at least some of the air exhaled or inhaled goes unfiltered with a surgical mask, it's well known by wearing one that this occurs and I don't know anyone that doesn't have this issue, though I don't know everyone.

[bladeracer]

I wear a mask made by Platatac, three-layers thick and fully enclosing the nose and mouth, making it very noticeably harder to breathe, and damned hot. I doubt I could run very far at all wearing it. Some places prefer I wear a five-cent surgical mask that has no discernible effect on restricting your breathing, so in those places I wear their crap mask under my good one.

In 2010 I was dead from a massive asthma attack when Rose got me to the hospital one night. I was six-hours on a ventilator in ICU with a nurse stationed by my side. I was then moved onto a ward as I stabilised, and I made a full recovery with no lasting damage at all. I have religiously stuck to my asthma medication since with just a handful of very, very minor incidents, requiring a puff of Ventolin and a few minutes rest from exertion to recover my breath.

I caught pneumonia (stalking foxes in horrendous weather for several days) and was moments from death in 2015, spending fifteen days in hospital with a cavitating abscess in my left lung that was turning my lung tissue into toxic waste and pumping it throughout my body. The respiratory surgeon who saved my life calls me Lazarus, because he never imagined me making any kind of recovery at all. Most unpleasant, for myself, and others, and not something I'm anxious to repeat by being around people that don't understand the basic principles behind wearing a mask, let alone having any care at all about what germs they might be spreading. I wear a properly-fitted mask for my safety, not anybody else's.

I think the vast majority of the public wear a mask because they have to, with no understanding of why they're supposed to. I avoided spending time in rooms full of strangers even before covid, if I have to wait to see somebody I wait outside in fresh air. Before covid it never occurred to me to simply wear a mask, I just preferred to avoid centres of risk, like pharmacies, hospital waiting rooms, public transport, and anywhere addicts hang out puffing on their drugs.

Despite my respiratory issues since childhood, I still lead a very active life, but I don't allow others to put me at risk with their complete disregard for the health of other people. In that regard I don't consider the mandatory masks rules to have been implemented in such a way that they would've had any measurable effect on the virus. The rules probably put people off hanging around others though, and perhaps served as an in-your-face reminder not to breathe around other people. But I don't believe they had much mechanical effect on preventing transmission.

Oh, my masks are woodland camouflage before anybody asks

[geoff]

The surgical mask is not the best tool for this job - it is said time and time again that the n95 is the preferred option.

Onto the question at hand, this isn't rocket science. A droplet, or a parcel of air being exhaled, is just a projectile. The surgical mask is admittedly doing one thing well - reducing the velocity of that exhale and any projectiles that may be caught up in it, as well as dispersijg it into several smaller parcels of air in different directions.

Shooters in particular shouldn't take too much nudging to figure out how this works to slow the spread of droplets. If it's leaving your face at a reduced velocity, it's not travelling as far. Remember how we were all social distancing really well for a while? The surgical mask is adding to that effect.

These measures are all tools that contribute various amounts of the effort of slowing spread in a community.

[Blr243]

We all admit freely that they restrict our breathing ( and we hate that with a passion) if it somewhat restricts the free flow of air into our lungs then it makes sense that it somewhat restricts other people’s covid containing vapour getting into our lungs ....I think they reduce sneeze and cough distance transmission of covid containing vapour .....masks can’t eliminate covid transmission but they can somewhat reduce the amount of transmission that would occur in none were being worn at all. The percentage of covid transmission reduction from masks is the unknown factor ...and depends on a few variables. Even If it saves one life it’s probably worth all the hassle of us wearing one ....fortunately for me I’m only wearing one occasionally when I have to go near people or enter a building . I do sympathise with retail or other staff who must wear them for 8 hours.

[womble]

Some strains of the flu have been wiped out for good because they weren’t up to the task with so many donning masks worldwide.
Didn’t get the flu season in Australia. Haven’t had a death here from influenza since the start of covid restrictions.
https://www1.racgp.org.au/newsgp/clinical/australia-records-zero-flu-deaths-over-past-12-mon
So i dont think you can underestimate the effectiveness of the basics. Masks, disinfectants, hygiene.

[Bugman]

I will just wear mine as a precaution etc.

[cz515]

I think Geoff and blade got the nail on its head. The masks esp the surgical are just trying to stop the spit droplets which are carrying the most amount of virus particles. So indoors in among children I would suggest even wearing a surgical mask is better than nothing.

Mate working in a very dust environment, I have always worn p2/n95 masks, but on recommendation by a doctor who does a lot of woodworking I tried a half face respirator and I suspect due to figment etc it is noticeably better, i go have a shower and clean my nose and I find I am not spewing out dark brown gunk.. sorry

It's heavy and sweaty, but that's a cost.. you eventually just get used to it.

[cz515]

I also wanted to add.

P2 disposable masks are obbligato good for a few hours, and shouldn't be taken off and on. Let alone wearing one over multiple days

So like you when I heard of wearing a bandana or surgical masks I went WTF. But it appears the scientists are mostly worried about the water droplets in our breath or when we speak, so even wearing a surgical one is better than nothing

[disco stu]

How do you increase the velocity of a fluid, such as air? Force the same volume through a smaller opening. If breath is leaking around the side of a mask it's probably going through a small opening and could be going at an increased velocity, potentially spreading breath further.

If it's leaking around the side, are any of those water droplets being caught? That's what I'm asking. It could be caught, but I don't know and it seems that no one has actually looked at it from the angle I'm coming from

I feel like everyone here is making the same assumptions that it seems the researchers make, and could be why this hasn't been looked at. I thought it would have been an important thing to at least consider and analyse. That's science.

Funnily enough, one article found that shedding of viral particles from ppe was higher than any other source, with the room where hospital staff donned and doffed their gear having highest concentration in the whole hospital. Highlighted what was mentioned by someone about playing with the mask. Whether that's is a risk still though is a different issue because they would have been dry rather than in the droplets of water

[Baronvonrort]

So there are a few things to mention. When we talk about masks it should always be properly fitted, esp around your nose and face...so as alluded to above no facial hair. When properly fitted almost all the air is going through the filter material, and I am not sure which makes of masks you use, all the ones I have seen, let air pass through. I have to wear a mask everyday related to my work (before covid) and I can assure you a good mask you can tell the difference in fitments and use, if fitted properly maskes work to filter the smallest dust or microbial particles as specified.

With regards to covid research, they all say is more about stopping the droplets as that's what got a large viral load, hence even wearing surgical masks is better than nothing.

So then you see people wearing the masks in shops, work places etc such that their nose is uncovered.... the mask is doing Jack all, and it's a tiny bit better than wearing nothing.

Yes if the mask doesn't fit properly it's useless this even applies to N95 etc facial hair does interfere with quality of fit.

The current research shows Covid is spread by aerosols so previous methods to contain droplets are not effective which also has implications for social distancing. Protection for droplets differs from protecting against aerosols.

Berlin made N95/PP2 masks compulsory as lesser quality ones aren't effective with covid.

I only use N95 masks.

In litigation prone USA they have this on boxes which is saying we warned you don't sue us if you catch covid.

[disco stu]

This thread has led to me trying some different search terms, leading to this article

https://www.nature.com/articles/s41598-021-91487-7

The authors seem to be critical of previous studies ignoring leakage around surgical masks, stating that there is barely any research on it, and specifically address one study that only looked at particles/water droplets in front of the masks by repeating their method but looking at sides, top and bottom. This was exactly what I've been looking for, do they work for all angles and if they do, why.

Basically, they did find a reduction from the sides and bottom, but no statistical difference at the top of the mask (hence the dramas of the poor long suffering glasses wearer's). Greater reduction in larger particles/water droplets, with less reduction in smaller particles. Smaller particles would be the ones that travel further.

Given the difference in particle sizes, they modelled things and concluded that inertia caused the larger particles to not take the turn out the side of the mask but to travel into it and get caught. I thought this might have been how it worked, if it worked, but before this one I wasn't even sure if it did work, and given what the authors say it seems no one else knew with any amount of confidence either.

Anyway, these authors seemed to have the same questions I did, and the same realisation that this hasn't actually been studied much if at all, getting quantified data.

I know my thinking can often be way out there, questioning things that people don't, but it seems everyone responding here has the same response as everyone else I've talked to-they filter the air, they catch the water droplets type of thing, how could you even question this. Feel a little more justified now

[bladeracer]

In California do the masks also carry the warning that they contain substances known to cause cancers?

So there are a few things to mention. When we talk about masks it should always be properly fitted, esp around your nose and face...so as alluded to above no facial hair. When properly fitted almost all the air is going through the filter material, and I am not sure which makes of masks you use, all the ones I have seen, let air pass through. I have to wear a mask everyday related to my work (before covid) and I can assure you a good mask you can tell the difference in fitments and use, if fitted properly maskes work to filter the smallest dust or microbial particles as specified.

With regards to covid research, they all say is more about stopping the droplets as that's what got a large viral load, hence even wearing surgical masks is better than nothing.

So then you see people wearing the masks in shops, work places etc such that their nose is uncovered.... the mask is doing Jack all, and it's a tiny bit better than wearing nothing.

Yes if the mask doesn't fit properly it's useless this even applies to N95 etc facial hair does interfere with quality of fit.

The current research shows Covid is spread by aerosols so previous methods to contain droplets are not effective which also has implications for social distancing. Protection for droplets differs from protecting against aerosols.

Berlin made N95/PP2 masks compulsory as lesser quality ones aren't effective with covid.

I only use N95 masks.

In litigation prone USA they have this on boxes which is saying we warned you don't sue us if you catch covid.

[disco stu]

So there are a few things to mention. When we talk about masks it should always be properly fitted, esp around your nose and face...so as alluded to above no facial hair. When properly fitted almost all the air is going through the filter material, and I am not sure which makes of masks you use, all the ones I have seen, let air pass through. I have to wear a mask everyday related to my work (before covid) and I can assure you a good mask you can tell the difference in fitments and use, if fitted properly maskes work to filter the smallest dust or microbial particles as specified.

With regards to covid research, they all say is more about stopping the droplets as that's what got a large viral load, hence even wearing surgical masks is better than nothing.

So then you see people wearing the masks in shops, work places etc such that their nose is uncovered.... the mask is doing Jack all, and it's a tiny bit better than wearing nothing.

Yes if the mask doesn't fit properly it's useless this even applies to N95 etc facial hair does interfere with quality of fit.

The current research shows Covid is spread by aerosols so previous methods to contain droplets are not effective which also has implications for social distancing. Protection for droplets differs from protecting against aerosols.

Berlin made N95/PP2 masks compulsory as lesser quality ones aren't effective with covid.

I only use N95 masks.

In litigation prone USA they have this on boxes which is saying we warned you don't sue us if you catch covid.

That is gold!

[disco stu]

In fact I'm wondering if the statement on those mask boxes is based on any research or data at all, or if it is just covering their butts if someone does catch covid while wearing them as mentioned

[Blr243]

The latter I think stu. A lot of people / companies are ever mindful of protection from litigation

[cz515]

Lol at blade, and as blr said is probably the latter.

I am not a fluid dynamics professor. For me though, my simpleton mind came up with this

Screenshot_20211221-140720_Samsung Notes.jpg (68.78 KiB) Viewed 4361 times

So the water droplets hit and either pass through or the pressure behind is large enough they might escape to the side but as material is absorbent the larger water droplets atleast are caught by the mask.

Now a lot of research has been done on masks pre covid, there must be a reason why surgeons wear surgical masks and not full respirators in operating theatre...esp In a litigation prone country like America. I am not intelligent or interested enough to search further into this. Esp when it see 60% of all people wearing masks outside wear the mask so that ot covers the most with their nose free.... the mask is doing nothing there. Look at the Asians they wear masks when outside and it covers their full face because they see benefit...we been forced to wear so we find dodgy ways around mask wearing mandate

[disco stu]

Instead of drawing pictures, put on one of the surgical masks and see how much air is blowing out the sides and top. I still think you just must not have experienced what I'm saying if you think most of the air is pushing through the material. This may the case if you're wearing the same mask you wear for work when out at the shops. Try a surgical mask if this is the case, especially with some glasses on-they'll fog up in no time unless it's really hot.

And just because a whole group of people does something doesn't mean automatically that what they do actually works. That's what science is, it questions assumptions to see if there is something in it. There are countless examples of people don't things that don't actually work or are stupid, especially when it's at a population level.

Yes, this research you mention I have actually looked at, as mentioned in the initial post where I outlined it. This research made the assumption that all of the air is pushing through the mask not around it. For this to occur the edges of the surgical mask would have to be glued to your face all the way around.

A reasonable amount of the research is post covid, but very little of it addresses the leakage around the mask, which is what this whole thread was all about. I know you said you don't really want to research this, but if you want to prove me wrong then find some data or something saying there isn't any leakage, which you seem to keep arguing. I've since found one that addresses this leakage and measured what happens, as described above. There appeared to be a few more, but way less than just assumed all the air passes through the mask and only measured it in front.

[cz515]

Mate I have worn surgical masks plenty. I have never had a mask that blocks half or more of the airflow. I think I said that earlier.

Maybe Bill can help I think he imports masks from China for medical use.

[Blr243]

Revolvers are not perfect , they lose some gas at the cylinder gap , but they still work good enough that I don’t want to be standing at the wrong end of one ( especially if Alec is hanging onto it ) Masks are never going to be perfect either , if they stop even some transmission, then that’s why we are having to wear them ...if there are not already scientific accurate test results on how effective they are , sooner or later someone will do it and we will hear about it

[Baronvonrort]

Lol at blade, and as blr said is probably the latter.

I am not a fluid dynamics professor. For me though, my simpleton mind came up with this

Screenshot_20211221-140720_Samsung Notes.jpg

So the water droplets hit and either pass through or the pressure behind is large enough they might escape to the side but as material is absorbent the larger water droplets atleast are caught by the mask.

Now a lot of research has been done on masks pre covid, there must be a reason why surgeons wear surgical masks and not full respirators in operating theatre...esp In a litigation prone country like America. I am not intelligent or interested enough to search further into this. Esp when it see 60% of all people wearing masks outside wear the mask so that ot covers the most with their nose free.... the mask is doing nothing there. Look at the Asians they wear masks when outside and it covers their full face because they see benefit...we been forced to wear so we find dodgy ways around mask wearing mandate

It is accepted covid is an aerosol virus by those who are up to date so warnings on mask box in the US reflect this reality as surgical masks are good for droplets yet useless with aerosols..

We aren't talking droplets with covid it has already been established it's aerosol which means all the previous ideas we had for droplet transmission are obsolete. With science when something is proved to be wrong it's chucked in the garbage and truth is embraced. The truth is they were wrong in assuming transmission was by droplets so whatever applies to droplet transmission isn't relevant with aerosols.

There has been plenty of research on masks i saw a good one recently which showed N95 masks aren't really effective if not fitted properly. I don't have covid so i don't wear a mask to protect others i wear one to protect me from others so it's minimum N95.

Airborne transmission = aerosols, droplets aren't airborne so here are a couple of links take note of the dates..
https://www.thelancet.com/article/S0140-6736(21)00869-2/fulltext
https://www.mja.com.au/journal/2021/australia-must-act-prevent-airborne-transmission-sars-cov-2

Germany is the only country that made N95 the minimum standard of masks for everyone with covid with their manatory mask rules.

[mchughcb]

Thanks Baron. I've read similar papers.

[disco stu]

That is interesting, and highlights my thoughts that I hope the workers in close contact with covid patients are getting good ppe.

One of the problems seems to be that going by what was in those articles and other things I've read, the virus is still likely viable for a decent amount of time, and sheds off the ppe when the workers take off the equipment. My understanding initially was that it "dies" if it dries out, and that doesn't seem to be the case

[Communism_Is_Cancer]

I once saw what I can only describe as a brain dead junkie driving in a car alone wearing a muzzle. This was on the sunshine coast several months ago. He probably had a boner and a smile on his face when he stood in line to hand over his rifle. Don't get bigger Stockholm syndrome than people like him.

[cz515]

Baron..... your first article clearly states that the authors are proposing the theory of aerosols.

The thing with research papers is people come up with ideas...theories, and then go about giving reasons in support of the theory. Then other scientists come read the article and try to prove it, either failing or winning. And that's why the article need to be taken in context.

That's why I prefer using authorative sources. Here researches or people expert in their fields give advice based on their expert knowledge.


Looking at the advice from CDC, WHO and our own RACGP the main forms of transmission is still classed as droplets with aerosol an important one as well. Now this is new and as things change and new information is found the advice will also change. But even if aerosols are the dominant factor droplets will still be important and stopping them would be better than having nothing.

Finally no one said you shouldn't wear a n95 mask... the only thing they say is wearing a mask of any sort is better than not wearing anything.