The Volokh Conspiracy
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Mask-Wearing in Airports Post-Vacatur
In Houston, about 5% of passengers wore masks. In DCA, about 20% are wearing masks.
Last week I was at the airport, and in the air, when the mask mandate was vacated and lifted. On Sunday, I took a flight from Houston. By my count, about 5% of the passengers in the terminal were wearing masks. On Tuesday, I flew back home from Washington National. By my count, about 20% of the passengers are wearing masks. Virtually all of the pilots and flight attendants were unmasked. The only people consistently masked were airport employees.
At this point, in the absence of a mandate, passengers wearing masks are doing so by choice. Yet, most of those masking up were wearing cloth masks. We have known since at least January that cloth masks are relatively ineffective against Omicron. They provide minimal filtering of the air you breath in, and because of the loose fit, are poor at blocking whatever you exhale. Moreover, people do not keep their cloth masks free from moisture, further decreasing their usefulness. Paper masks are marginally better, since they are disposable. But again provide minimal filtering, and often have poor fits. Starting in January, I had switched to wearing N95 masks exclusively. If I was wearing a mask, I wanted to wear something that would actually provide protection against the new variant.
Gary Leff from View From The Wing asks why passengers are sticking with the ineffective cloth masks, even in the absence of the mandate:
What I didn't understand was that a majority of people who were wearing masks were wearing either cloth or medical masks. I understand why people don't wear masks. And I understand why people choose to wear them when they are no longer required – to protect themselves – but I do not understand the choice to wear a cloth mask, which doesn't provide that protection.
Those who are critical of the mask mandate's end point out that masks protect the people around you from you, if you're infected, and the infectious period of Covid-19 prior to showing symptoms. Cloth masks didn't help with this. Medical masks likely do little against current variants. But better masks do help.
Perhaps cost is a factor. Though I think people who can afford to fly generally are able to purchase better masks, if they so choose Discomfort may also be a factor, as N95 masks may be tougher to breathe in. (I found the N95 pouch variants yielded the least amount of fog on my glasses.) But on balance, I don't understand why passenger who voluntarily wear masks are sticking with cloth masks.
I think these same questions exist for people wearing masks in other contexts where they are not mandated: why stick with cloth masks that are not effective against Omicron?
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It is presumably virtue signaling. "I'm one of the good people who wear masks, not the mask-less barbarians who want grandma to die". Seems pretty ignorant to me to wear a cloth mask at this point.
When I am required to or choose to wear a mask, I usually wear a KF-94 as I've found they have the best balance of comfort and functionality. Currently I only choose to mask on crowded subways, elsewhere I wear them where required or where it will make friends happier.
Da5id — Virtue signaling and vice signaling both have their points, pro and con. Discuss.
Meh. Wearing a cloth mask given what is known signals simple ignorance rather than virtue IMO. As does wearing a mask outdoors. And "virtue signaling" usually carries a sense that the act is in some way false or insincere.
When masking was mandatory I ware a cloth mask and it was very effective - people stopped yelling at me.
Some places have wised up to this and required N-95 equivalent masks. Examples include local social dances that still require masks. I'm totally fine with private groups (e.g. those running these dances) picking their rules and people then getting to choose whether to attend those events given the rules. Silly government mandates are more my issue.
Same here. And I found the most breathable mask I could buy (BreatheFreely). That way I could be comfortable while providing the same protection from the virus (aka none) and wokists (aka a lot).
Alternatively, they're libertarian types worried about government surveillance (5% seems about right). A smaller contingent may be criminals, or otherwise up to no good.
"It is presumably virtue signaling."
Rather presumptuous of you. 1) JB did not note whether the cloth mask was over a surgical mask or any other mask. He just did a crude estimate. 2) Some number of people of order of 10% to 20% are immuno-compromised to some degree or have other medical conditions that put them at risk.
So who are you to judge?
If you say someone is "wearing a cloth mask" it is fair to infer it isn't over a surgical one. Or that would probably be mentioned. And cloth masks are of little value. So sure, it *could* be plain ignorance rather than than virtue signaling.
And anyone who is significantly immunocompromised who is wearing just a cloth mask for protection needs some real education. In fact, I'd imagine such people are rare at this point. If you can afford an airline ticket you can probably afford KF-94/N-95 level masks.
And I don't judge people for wearing *functional* masks in most circumstances. Outdoors masks seem really silly to me (again probably ignorance about risk factors). Indoors I think they mostly aren't needed for *my* safety at this point, but I'm not at all bothered or judgmental about other people taking what seem to them to be reasonable precautions for *their* safety as long as they aren't trying to dictate my choices. And I'm also OK with people who are hosting events or running businesses coming up with whatever rules they like w.r.t. masks and people deciding whether to attend or not accordingly. I'm just pleased the government is mostly out of the way of that. I am perfectly willing to attend masked events, and attend a number weekly.
Outdoor mask are silly. Air circulation forced either by winds or body movement are far more effective at dispersing the aerosols
And solar UV kills the virus FAST -- as confirmed by Homeland Security's research department, who tested to find out whether this virus has the same sensitivities as other enshrouded-RNA viruses (mildly sensitive to temperature, quite sensitive to humidity, and VERY sensitive to UV) [Note that this gives the lie to "good faith" claims for the establishment: the government knew that there were other measures both much more effective and much less intrusive than masking and social distancing.]
Not arguing with the general point that masks are unnecessary outside, but I will note that it's possible to go outside at night time in which case solar UV is not going to be helping you at all.
That is true but the air citculation due to temperature variations between structures ground and air is quite large and extremely effective in making viral concentrations very low
That was well known before the DHS stepped in.
"But on balance, I don't understand why passenger who voluntarily wear masks are sticking with cloth masks."
I think masks are very useful. They clearly identify the Democrat douche bag in the room. I have proposed requiring double N95 masking, that really fit snuggly, for all children and adults in all Democrat jurisdictions.
Pouch variants. Everyone wants a mask which makes it easier to breath. Everyone, that is, except the few folks who understand that ease of breathing is synonymous with reduced protection. Think about it. If your mask filters 95% of some standard particles, the more air your mask allows to pass, the more particles come with it. No matter how well they seal, and no matter whether they pass the N-95 standard, other things equal, masks with more surface area will pass more virus.
So....masks really are ineffective.
No, he did not say that. But if your glasses fog up the mask is not sufficiently well fit.
Still the mask does reduce the number of virions that get into your lungs, the question is by how much. Some masks are totally ineffective some do a good job.
I truly hate the mask fogging up my glasses, Don Nico.
So do I. But I find it not so difficult to adjust the mask(s) to avoid it.
That is a phenomenally stupid comment even by your standards.
No matter what kind of mask you wear (or don't), you need to suck in the same 3-6 liters of air per breath. That means for a given quality of mask, you're going to inhale the same quantity of virus particles either way.
The difference between the "pouch" masks and softer masks only matters to how hard you have to work to get those 3-6 liters in and out. A soft mask will be mostly in direct contact with your face - only the square inch or two directly in front of your mouth or nostrils will actually be passing air back and forth. A more rigid "pouch" mask will stand out from your face and exploit the pressure differential created by your breathing to pass air back and forth through the entire surface - call it roughly 24 square inches.
Either way, the same amount of air and (again, for a given quality of mask) the same leakage of particles. The only difference is in ease of use.
Well, plus the "pouch" masks tend to stay in place a bit better but we can ignore that factor for now.
Rossami, you're thinking about the science. Stephen is talking about The Science. We all need to understand the difference now.
Ducksalad - you forgot to put "The Science" in quotes - though comment remains valid.
"The Science" is a religion
I have been blasted on the blog frequently for stating that masks are very ineffective, yet none of the believers in "The Science" have been able to point to a single empirical study using real world data that shows that masks are effective.
Yes, "The Science" creed is practiced by Branch Covidians.
speaking of branch davidians - I worked on a 2 week project directly across the road from them about 4-5 years prior to the atf raid. very common for them to be shooting off weapons on their firing range. The locals just thought they were strange nuts.
Joe,
As I have pointed out many times to you, the so-called "real world data" are meaningless when it is uncontrolled the the methods in which masks are used, the types of masks, the measurements that are made, etc.
Every time someone points out carefully controlled experiments in which the masks are tightly fit and must filter all air that passes and in which the from and rear surfaces are not cross-contaminated, you complain that those tests are not "real world data."
What you call "real world data" is actually only anecdotal and not in any sense a well structured, scientific investigation of the efficacy of mask filtration.
Do many people get that benefit? Obviously not. That is not science; it is human falibility.
Don - As I have repeatedly pointed out to you and to everyone that points out the perceived error - The highly structured controlled lab tests which you refer to are not what is happening in the real world.
Theoritically, those highly structured lab test should be meaningful. yet since that is not what is happening in the real world they are meaningless
That's not how any of that works, Joe.
"Studies show seat belts save lives."
Joe: "But not everyone wears seat belts, so they're useless."
No Jason. Bad analogy
Seat belt saves life.
Everybody is tying a rope around their waist and calling it a seat belt. So all the studies that say seat belts work, are meaningless, because 99% of the users are not using the seat belts being used in the study.
Or we could say that studies of NASCAR drivers show the survive-ability of crashes at 100 mph is very high so we can raise the speed limits to 100mph with no increase risk of death. Since NASCAR uses seat belts and all cars have seat belts, so we can extrapolate the study.
Joe,
That is exactly what I said in my comment. That people act like fools does not mean that the advice is wrong. Don't confuse the two.
Lab tests are NOT meaningless. What people do with them is stupid. You are falling into a common epistemological error.
But, the only place calling for the cheap paper medical masks are medical. All the other places are fine with cloth. Almost all the people voluntarily wearing masks are cloth and wearing them wrong.
There is talk of N95, but I have never seen a PSA explaining what is proper for the most safety. Which includes...no more the 2 hours?
But its all a show. A wink and nod. The people wearing them know they aren't effective and everybody gives them Emperors new clothes treatment.
"Almost all the people voluntarily wearing masks are cloth and wearing them wrong."
This may be a regional thing. Locally, maybe 10% of people still wear masks, and almost all of those are N95.
Which are effective. If you don't think N95's are effective enough, you can always get an N100, which is 5/.03=166 times more effective than an N95.
Again, just because people are stupid does not mean that the requirement or recommendation is stupid
" "The Science" is a religion "
You make that sound like a bad thing. I thought gullible, obsolete right-wingers liked and respected religion -- even the silliest religion.
Rev, you still talkin', Groomer? You need to STFU. First, resign from your law firm, then, interview the diverse replacement. You stole your seat in law school, and then that job by having your white privilege.
Actually Rossami is thinking about his fantasy. He obviously has never used a tea strainer.
You mistake volume, which is the same, for pressure, which causes the discomfort. A larger surface area is analogous to a larger pipe though which you pass the same amount of water. The larger pipe requires less pressure (pound per square inch) to pass the same volume of air. The amount of virus in the air is a constant. Passing half of that volume through each half of a twice as large area means the same amount of virus is filtered out either way.
CJ, the proper measure is not discomfort, which is subjective. The proper measure is aerobic capacity, which can be measured directly, or indirectly by tests of performance.
And your critique is circular. You presume equal volumes of air. The contention you are asked to refute is that different mask designs do not, in practice, deliver equal volumes of air, so you are not entitled to that presumption.
"You presume equal volumes of air"
Can you explain how you think wearing a mask changes your body's oxygen requirement?
Absaroka, I do not have the same oxygen requirement from moment to moment. It changes according to activity level.
Plus which, if the oxygen must be metered through sieves with varying dimensions, knowing the amount required tells me nothing about the rate at which the requirement can be met.
Rates and amounts are not the same. Other things equal, smaller sieves will support smaller maximal rates, and deliver smaller amounts. Larger sieves will support larger maximal rates, and deliver larger amounts. Virus exposure will depend on amounts primarily.
Why is this hard?
"Why is this hard?"
It's not.
Stephen, it isn’t a presumption; it’s a stated part of Rossami’s comment and he is right about that. You breath the volume of air you need to fill and empty your lungs. If you breath it through a larger surface area, each square inch of the mask will pass a smaller portion of that volume and will have to filter a correspondingly smaller portion of whatever is being filtered. Your lungs will have to exert less pressure to move the air, which should be objectively more comfortable, all other things being equal. Finally, since a smaller amount of air is being passed through each square inch, the velocity of the air and any particles will be lower and the filter should be more effective. (That last part may be offset if the makers of the mask used less effective filter material.)
Except that the air inside the mask has higher CO2 and lower O2 than the air outside. This means that you need to breathe in MORE air and also suffer the cardiovascular stress of the extra CO2.
" the filter should be more effective"
how did you get to that? The effectiveness is independent to air velocity over the relevant range.
"No matter what kind of mask you wear (or don't), you need to suck in the same 3-6 liters of air per breath. That means for a given quality of mask, you're going to inhale the same quantity of virus particles either way. "
Buddy, you are dead wrong. Have you ever used any kind of sieve for any purpose whatsoever?
Learn to read: " for a given quality of mask, you're going to inhale the same quantity of virus". Or in your simplistic lingo, for a sieve of given hole sizes, the same amount of particles is going to get through, whether you use a large sieve or a small one.
ZZZ wake up and learn to think.
I am awake, thanks. I explained your mistake to you. read it slowly and maybe you'll understand.
As i said learn to think.
Yes, many times. Have you?
Here's an experiment for you. Take 1 pound of water. Dissolve 1 pound of sugar into it. Find two sieves, one large and one small but both with the same tightness of weave. Pour the sugar water through the large sieve and weigh the result.
Since all the dissolved sugar will flow through your sieve no matter what the weave, you better get 2 pounds. Now pour the same sugar-water through your small sieve. Being smaller, it will take longer but you will still have 2 pounds at the end. The amount that gets caught by the sieve is dependent on the tightness of the weave, NOT by the surface area of the sieve. The surface area ONLY determines how long it will take (or, if you constrain time, how much pressure you have to apply to get the same volume through in the same time).
Rossami, you seem to suppose for this comparison that sugar dissolved in water is analogous to particles suspended in air. I doubt that works.
For the purposes of understanding the point, it does not matter whether the filter is 100% effective or 0% effective. The point is that the effectiveness (whatever it is) is dependent solely on the tightness of the weave of your sieve and not even slightly dependent on the size of your sieve.
But you can do a different experiment. Use pulpy orange juice. Use two sieves of the same tightness of weave, one that's 2 inches in diameter and one that's 4 inches in diameter. Assuming they are roughly the shape of a symmetric cone, that works out to 9.5 sq inches and a shade under 38 sq inches respectively.
The bigger sieve will definitely process your quart of juice faster (or, if you force it through in the same time, take less pressure), but you'll have exactly the same volume of juice at the bottom and exactly the same amount of pulp in the sieves.
Proving what exactly? If the holes allow all the pulp to be trapped in both cases the volume in the receptor beaker will be equal.
IF the holes are of sufficiently different size that one traps plup and the other does not the volumes will be different if the same volume of liquid is introduced to both seives
Rossami,
You really need to take (and pass) a course in physical chemistry. What you describe is a bogus (irrelevant) experiment.
Have some real knowledge about matters before you comment
Nico, I invite Rossami to try a demanding aerobic workout two ways, without any mask, and with N-95 mask. I suggest twenty 100-yard sprints, starting each sprint 20 seconds after you started the previous one. Or reduce the number of sprints according to your athletic capacity. Do the test with a day or two of rest between tries. Use a stop watch to measure your cumulative resting time. See how you perform unmasked, and then masked.
From what Rossami says, I presume he may never have worn an N-95, or maybe any mask. It is hard to believe anyone who uses an N-95 routinely would conclude you get the same volume of air masked as otherwise, or that differently designed masks do not affect the volume of air available.
Rossami, at my present age my aerobic capacity is not as great as it once was. Still good, still getting up and down stairs without getting winded. But when I was younger I had more reserve aerobic capacity than I do now. When you get older, you will have less capacity too.
It may be your reserve aerobic capacity is still so high that it makes you subjectively insensitive to a casual, insufficient aerobic test. After a rigorous test shows you the difference, you ought to be able to infer that differences in mask design will affect the volume of air available, and thus affect virus exposure.
I have done this and more. You are wrong. If you want to really test it, don't use just a dinky N-95 mask. Run your daily PT (physical training) in MOPP-4. A full military gas mask is a LOT harder to breathe through than any of the masks we're talking about. Despite being harder and a lot more tiring, the volume of air you need to move in and out of your lungs is the identical. You do not start to breathe more shallowly or have some miraculous transformation in how your body processes oxygen just because the muscles in your diaphragm and ribs have to work harder.
Yes, aerobic capacity declines with age. Since we're comparing mask vs no-mask at the same age, that has nothing to do with this issue. Yes, wearing a mask is tiring. It does not change the volume of air.
" Despite being harder and a lot more tiring, the volume of air you need to move in and out of your lungs is the identical. "
Which proves exactly nothing with respect to how many virions go into your lungs.
You could change the volume of air by adding a small oxygen pack
Do a measured test, Rossami. Then report. If you think an N-95 is dinky, give the 20 sprints test a try wearing one. I predict you won't make it without tearing the mask off. Or maybe you can, without sprinting, by turning it into a continuous 2,000 yard run. But not if you play the game according to the rule, to maximize rest time.
The volume of air a person needs to move in and out is not a constant, except minimally. It is possible for one filter to restrict air flow to minimal amounts, while another filter passes larger amounts in the same time. The minimal filter will permit only minimal performance. The other will provide greater performance, allowing full use of the aerobic reserve most folks are born with. Thus, greater performance will result from larger air volumes, but with Covid, that comes at the cost of higher virus exposures.
Why is this hard?
What a bizarre non-sequitur.
"It is hard to believe anyone who uses an N-95 routinely would conclude you get the same volume of air masked as otherwise,"
1)I have used N95 and N100 masks for many years. The fabric ones, the rubber ones with canisters, etc, etc.
2)Rossami's point is that if you need 3 liters of air to supply enough oxygen to survive, you either get 3 liters of air or you become hypoxic. You may have to work harder to pull in that three liters through a mask, but you are going to get it or pass out. And *it doesn't matter how many square inches of XX% effective filter media you pull 3 liters of air through, you are still filtering 3 liters of air at XX% efficiency* [1].
3)I'm trying hard to try and grok what you are saying. It almost sounds like you think filters work by reducing airflow instead of filtering it. I mean, in one sense that's true, if you pull a plastic bag over your head you will be 100% protected against covid, but you will also suffocate. Masks work by removing contaminants from the air. They don't reduce your need for oxygen/the volume of air you have to breathe to survive.
4)As an aside, masks aren't screens that keep out mosquitos larger than the mesh, or tea balls, or sieves. They work electrostatically. The whole 'pore size vs virus size' discussion misunderstands the mechanisms at work.
5)Just think about what you said originally: "other things equal, masks with more surface area will pass more virus". If that was true, would a mask filter better if you used duct tape to cover all but a 1 square inch section of it? When the filter media was in short supply, why did manufacturers keep making the whole mask out of filter media?
[1]You could posit second order effects based on static pressure or velocity effects, and I'm glad to look at whatever data you have on those (as opposed to deductions out of the aether), but generally speaking I would expect those to favor the larger surface area filter because it would reduce the static pressure and airflow velocity.
Of course, the issue is NOT how many gas molecules pass through the mask but how many virion-bearing aerosols do.
The area does matter in that the over or underpressue on the wearer side and consequently the dynamic tightness of fit does vary.
"The area does matter in that the over or underpressue on the wearer side and consequently the dynamic tightness of fit does vary."
So the theory is that with a fairly impermeable mask, you can inhale sharply enough to get a momentary seal? And that adding surface area that would lessen the pressure imbalance would mean it doesn't collapse as tightly on your face?
I dunno. With a good mask (especially, say, the ones that have a rubbery face seal around the perimeter like, say, a 3M 8212) with straps you can cinch down tightly enough to leave a crease in your face, you shouldn't be getting much leakage. That seems more reliable than depending on a transient vacuum when you inhale.
When I put on a mask, I do a sharp inhalation, and you indeed should feel it pull in to your face. But I'm not breathing that hard walking around the grocery store; I don't think there is much of a pressure differential then. I think I'd rather just tighten the straps.
"When I put on a mask, I do a sharp inhalation, and you indeed should feel it pull in to your face. "
Agreed, if you do that at the beginning of your inhale you will increase the effectiveness of filtration.
Forgive me, but I'm still skeptical that altering one's breathing pattern to sharply inhale (and presumably slowly exhale?) is intended by mask designers. It certainly not mentioned in the instructions for any of the masks I have used. They go into a lot of detail about fitting and using the mask, but that kind of altered breathing isn't part of the instructions. Those instructions are about eliminating leakage regardless of whether you are breathing hard or not.
I also doubt that the mask designers take that into account. It is an automatic feature of the relevant physics.
Absaroka, why would anyone suppose the volume of air needed to survive is the only volume of air relevant to using a mask—or relevant to limitations which different masks might impose on activity, by restricting to different degrees the wearer's access to oxygen?
Do you suppose with all other factors equal, that the rate of maximum fluid flow through a small-area sieve is identical to the maximum rate which can go through a large-area one? Intuitively that sounds like nonsense. Mathematically, I expect you might find tricky exponents in the equations.
Or alternatively, why would anyone size pipes differently, if not to match their capacity to the rate of flow they are expected to accommodate?
"why stick with cloth masks that are not effective against Omicron?"
Because you can't fix stupid. Like the people walking alone on empty streets or alone in their car with the windows rolled up who wear masks.
"Because you can't fix stupid. "
Ah, yes. That is the cause of many of our society's problems. Too damned many stupid people.
A drive through any shopping center parking lot proves that.
The masks are a signal that you despise Trump and the Republican yahoos. It's not surprising that you see more of them in DC than in Texas. Of course, the signal imposes some cost, and so even some of those who share the aforesaid sentiment don't have enough invested to wear a mask.
If the mask fogs your glasses at all, you are getting/giving no protection.
Before it went full fascist, the CDC advice on masks was closer to correct:
"If you are sick," the CDC says, "you should wear a facemask when you are around other people (e.g., sharing a room or vehicle) and before you enter a healthcare provider's office." But "if you are NOT sick," it adds, "you do not need to wear a facemask unless you are caring for someone who is sick (and they are not able to wear a facemask).
...of course this was subject to change without notice.
"If the mask fogs your glasses at all, you are getting/giving no protection."
I'd agree that you are obviously getting less protection. My experience disagrees with 'no protection'. I base this on years of using masks for welding, sanding drywall, and in recent years during episodes of dense wildfire smoke. Even with some air leakage my highly scientific metric of 'how dark the kleenex gets' suggests non trivial protection even with some air leakage. In fact, the kleenex test results are dark for no mask, and not dark for both no leakage and a little leakage; the kleenex looks the same for both of those.
Less leakage is better, but a little leakage is better than the 100% leakage you get with no mask. As Rossami correctly notes above, you inhale/exhale maybe 3 liters of air per breath. Your glasses fogging a little doesn't mean you are pulling 3 liters of air in past your nose when you inhale. You'd notice that much flow in such a small area.
Some of what you say may be true but we are talking about a virus that is smaller than what even an N95 mask is designed to block.
"... we are talking about a virus that is smaller than what even an N95 mask is designed to block."
Here's what OSHA has to say about that:
"Yes, an N95 respirator is effective in protecting workers from the virus that causes COVID-19. "N95" refers to a class of respirator filter that removes at least 95% of very small (0.3 micron) particles from the air. Some people have mistakenly claimed that since the virus that causes COVID-19 is approximately 0.1 microns in size, wearing an N95 respirator will not protect against such a small virus. That mistaken claim appears to result from a misunderstanding of how respirators work...
The National Institute for Occupational Safety and Health (NIOSH) tests respirators using particles that simulate a 0.3 micron diameter because this size particle is most likely to pass through the filter. If worn correctly, the N95 respirator will filter out at least 95% of particles this size. An N95 respirator is more effective at filtering particles that are smaller or larger than 0.3 microns in size."
Why would a smaller particle be less likely to pass through the mask?
I think Absaroka lost a bit of the explanation to copy-paste. Or maybe the OSHA website just explains it badly.
An N95 mask will stop 95% of particles that are 0.3 microns in size. The same mask will stop more (but not necessarily all) particles that are larger. It might also stop 99% of particles that are 0.6 microns and 99.999% of particles that are 1.0 microns. That same mask will also stop some (but definitely not all) particles that are smaller. it might stop 80% of particles that are 0.25 microns and 60% of particles that are 0.2 microns. Rather than give people real data - a chart with a curve showing how much at each size really gets filtered, the regulators and manufacturers assume that we are stupid and can only understand "N95" and try to distill the entire concept down to one number.
Sorry. Let me get off my soap box. The point is that every mask type has this same basic curve, just with different values. So if your N95 mask will stop some (but not all) particles smaller than 0.3 micron, an N99 mask will stop more of them and an N85 mask will stop less of them.
The N95 is "more effective" than a cloth mask at blocking really small stuff is a true statement because "more effective" is a relative statement (and, in this case, a very low bar).
Rossami, your comments show singular faith in plausibility as a standard of proof. I will not call you stupid for that, just suggest that there are smarter ways to think about practically everything, than to rely on explanations because they sound plausible.
Here's a wiki article describing the different mechanisms, which vary by particle size (see the 'Mechanism of Operation' section.
They have an idealized chart of efficiency vs. particle size, which parallels real world charts I have seen.
The article explains: "A HEPA filter must remove at least 99.97% (US) or 99.95% (EU) of all airborne particulates with aerodynamic diameter of 0.3 μm. Particles both smaller and larger are easier to catch, and thus removed with a higher efficiency.[6][7][8] People often assume that particles smaller than 0.3 microns would be more difficult to filter efficiently; however, the physics of Brownian motion at such smaller sizes boosts filter efficiency".
I claim no particular expertise, but that is the explanation I usually hear, for HEPA, Nxx, and high MERV filters, all of which have similar curves.
" however, the physics of Brownian motion at such smaller sizes boosts filter efficiency"
That sounds reasonable up depending on the gas flow parameters through the filter.
Nico, a further factor which I have seen cited is that N-95s are treated to provide static charge protection, to which smaller particles may be more sensitive. That is also cited as a reason not to reuse N-95s, because that static charge degrades with use.
That is correct SL Although GUV was shown very early by Batelle, to disinfect the mask after one wearing without damaging the filtration capability.
No so fast bumble. The virus is transported on aerosols the size of which is large than the N95 pore size.
I think you are falling into the common fallacy of confusing droplets for aerosols.
Here's a good test:
Inhale a vape. Then exhale through different types of masks. The "smoke" you see penetrating is pure aerosol.
Sure, if you sneeze a mask will capture the droplets you expel, Aerosols are a completely different story.
Not at all, CurrentsGuy. The droplets are huge. Even most multi-layer cloth masks stop those. I have seen size distributions many times; I understand the physics involved in the hydrodynamic transport as a function of size, weight and density.
Your "good test" is a banality.
In the future don't assume what I do not know.
The particles generated from welding, sanding drywall and smoke are larger than a virus, so the mask offers some protection from them.
1)You might want to read some of the references above.
2)I offer those examples not as some comment on particle size, but on how much unfiltered bypass is occurring when your glasses are fogging. When we're talking about unfiltered bypass, particle size isn't relevant,
Your glasses fog because the pressure inside the mask exceeds that outside during exhaling.
When you inhale, the inner pressure is lower tightening the seal. therefore the leakage in and out is not symmetrical. If you are protecting you neighbor it is the exhaling leakage that is important.
If you are inhaling the inhaling leakage is controlling.
No disagreement there.
"no" was an exaggeration. but "less" or even "much less" would be more accurate
Prof. Blackman - the effectiveness of the mask is not modulated in any way by the "variant." Cloth masks are equally ineffective against Alpha/Beta as they are against Omicron. These viruses are identical in size and mechanism of transmission.
I guess disinformation can fool even highly educated people (that would be you Prof. Blackman).
Obviously you're right about the physical filtering effect being the same.
But, depending on one's philosophy of risk management, the difference in contagiousness and virulence could make a difference.
Omicron is more contagious but less dangerous, therefore one might decide that unless a mask is really going to stop it, it's not "effective". Alpha was less contagious but more dangerous, so even a partial mitigation of risk might be worth it.
Variant — A moment's thought might suggest that viruses which vary in virulence would require less protection for the less virulent. So for the same volume of exposure, the less-virulent viruses might be protected against, while the more-virulent viruses would not.
I flew out of LAX over the weekend---after LA County had reimposed a mask mandate for airports (not airplanes), bus terminals, etc. Outside of airport employees, five to ten percent wore masks of some sort. Obviously, nobody was enforcing the local mandate. About the same percentage wore masks on the plane. None of the crew wore masks.
"Masks are not only tools, they are also talismans that may help increase health care workers’ perceived sense of safety, well-being, and trust in their hospitals. Although such reactions may not be strictly logical, we are all subject to fear and anxiety, especially during times of crisis. One might argue that fear and anxiety are better countered with data and education than with a marginally beneficial mask ..."
Klompas, Michael, et al. "Universal masking in hospitals in the Covid-19 era." New England Journal of Medicine 382.21 (2020): e63.: https://www.nejm.org/doi/full/10.1056/NEJMp2006372
It could be "'virtue signalling", but more likely it's just a security blanket. It makes people feel better. Whether it actually works against virus transmission is beside the point. The real question is does it work against virus anxiety.
DaveM, as a consistent mask wearer during the pandemic, over more than two years, I have not suffered a single cold, not even a sniffle. Normally, I would rack up about 3 colds and one episode of severe bronchitis per year. So wearing a mask has in that respect made me feel much better.
Stephen,
Although I advocate mask wearing, and try hard not to do so in a stupid manner, the mask generally slides to some extent especially those with ear loops. Adjusting the mask does invariably lead to cross contamination front to back.
Despite double masking except when sleeping when I single masked I did come down with nearly asymptomatic COVID, most likely made more likely because I am moderately immune suppressed.
Nonetheless I strongly suggest masking about aircraft, especially if one's medical condition makes one more susceptible than average.
This does NOT prove Joe's claim that masks don't work. It only shows that no method is 100% effective.
That is reasonable. It also could be a bit of both. I do think a goodly number of people have acquired a phobia about being in groups unmasked that takes a bit of time to unwind.
You are right about the virus anxiety element.
However, to the extent that masks did not work as well as claimed — for all but N95, the gulf was huge — people invariably took risks they were unaware of, in that they did things with masks they wouldn't have done if they were aware the mask they were wearing was useless.
And there is a further issue. Let's say that an N95 mask removes 95% of virions in a single breath cycle. That absolutely does not mean that the risk of infection is reduced by 95%.
I found that I could get about three or four weeks use out of a disposable paper mask before it eventually fell apart.
If that is the way you use a mask, then you are getting little to no benefit.
Josh, are you wearing an N95 mask, which is certified to meet standards set by OSHA and the EPA, and is a registered medical device, or are you wearing KN95 masks, made in China and they promise they are almost as good?
What was great was watching people in the airport wearing a cloth mask post-mandate with the mask pulled down from their nose but still covering their mouth. Why are you still wearing a mask, and if you insist on wearing a mask, why are you doing it incorrectly?? Boggles the mind.
"pulled down from their nose but still covering their mouth."
I saw exactly the same thing. Then the mask is useless.
It is useful, like asking people to voluntarily wear a dunce cap. I hope the trend continues.
1) I strongly suggest that people try to internalize the most important meta-lesson of science, which has enabled it to explosively transform our world much more in the past 300 years than in the preceding 200,000 years despite the fact that human brainpower was roughly constant over that entire period: An attitude of humility concerning how certain is each piece of our knowledge and how to learn more.
2) Slightly off-topic but relevant to reducing air travel infection risk: I find it plausible that for any given level of personal and general passenger masking, aiming the cabin air nozzle at one's face is a good way to reduce COVID infection risk. That is because a) there is higher infection risk when one inhales large viral loads, b) commercial airline air filters are at least somewhat effective at filtering out viral particles, so c) to the extent one is breathing a steady stream of just-filtered air rather than unfiltered, relatively stagnant air, the combination of air movement and filtration reduces the chance of inhaling a particularly large viral load just exhaled by a nearby passenger. Comments invited.
arch1,
It is fine to aim the nozzle at your self. The airflow is down from the top of the row to the intake at the bottom. There is little airflow along the axis of the cabin.
The biggest problem is during the times when the engine is shut down; that means during boarding and landing. That is also when the density of people is highest, when air circulation is minimum to scarcely existing, and therefore when viral load in the air is highest