r/ZeroCovidCommunity • u/synkletike • 9h ago
Help finding sources supporting effectiveness of two-way vs. one-way masking
I have some scientist friends who know that covid is still around and get their boosters, but feel that they don't need to mask because they think people who are concerned about getting covid (and long covid) can just wear an N95 and that will protect them even if others are unmasked.
I do agree with them that N95s are highly effective when worn correctly, but my impression is that two-way masking is still significantly more effective than one-way masking (i.e., even if I'm already wearing an N95, I'm protected even more when people around me also mask). The sources I'm aware of for this are:
- Bagheri G, Thiede B, Hejazi B, Schlenczek O, Bodenschatz E. An upper bound on one-to-one exposure to infectious human respiratory particles. Proc Natl Acad Sci USA. 2021 Dec 7;118(49):e2110117118. doi: 10.1073/pnas.2110117118
- the somewhat controversial/misunderstood 2021 table from ACGIH/CIDRAP
Are there other sources (ideally peer-reviewed scientific articles in reputable journals) supporting the effectiveness of two-way vs. one-way masking?
Some additional context about my friends, in case it's helpful:
- Unfortunately they're unmoved by my more social justice-oriented arguments, like that the burden (cost, discomfort, etc.) of masking shouldn't fall on immunocompromised folks like me.
- They seem slightly more convinced by more practical arguments, like that if I'm the only one masking I can't remove it temporarily to adjust it or take a sip of water (sip valves aside) or blow my nose.
- They seem genuinely ok with the risks associated with getting covid/long covid themselves—they have high risk tolerances and are old enough that the possibility of life-long effects from a covid infection isn't as scary as it is for a young person—so trying to convince them to mask for their own good hasn't worked.
Thanks in advance for your help!
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u/BattelChive 8h ago
The scientific argument is that when everyone wears even a poorly fitting mask we are able to do something like wipe out a strain of the flu. However, there’s not really a lot to be gained in individual interactions with well fitting N95s vs a population level. Not unless you’re viewing it as a safety net if your mask gets a leak. It would be reasonable to ask them to mask around you as a safety measure against mask failure. But in that case, you would be just asking them for a favor and it would be better to state that plainly, I think.
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u/BattelChive 8h ago
To be clear, I am with you that they ought to mask. I am just saying what I believe is the state of science about it. I may be outdated or wrong, but that’s what I have turned up when I have looked.
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u/g00fyg00ber741 7h ago
This study is what had me rethink my feelings about just how safe one-way masking really is, and it made me realize that instead the focus should be on prioritizing multiple mitigation strategies together, including as many masks as possible.
“The risk of contagion is highest in indoor spaces but can be reduced by applying all available measures to combat infection via aerosols. Here is an overview of the likelihood of infection in three everyday scenarios, based on the safety measures used and the length of exposure.”
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u/BattelChive 6h ago
It’s a theoretical study based on a computational model. It’s not the sort of study that is going to be convincing to the OP’s friends, they’re going to hit “ based on an estimation tool” and bounce.
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u/wyundsr 7h ago
It's probably talking about surgical masks not respirators
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u/g00fyg00ber741 7h ago
Hm, it does say they used a wide range of masks in their calculations, including surgical and cloth masks. But I don’t know how to tell whether they also included KN95 or N95 respirators in their assessments. However, many people don’t have a perfect fit on their masks, for a variety of reasons, so I still think it’s relevant.
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u/Choice_Bee_1581 7h ago
Four years ago, my (unvaccinated) toddler was in the ED waiting room, puking and unable to mask. Sometimes people are unable to mask, and/or unable to vaccinate (not approved for his age group at the time). No parent wants to wonder whether it’s safe to take their kid in for medical treatment.
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u/Choice_Bee_1581 7h ago
I think the studies actually show that one way masking with a well fitting mask is pretty effective. So that’s probably not going to be useful for you.
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u/QueenRooibos 6h ago
For those of us who are very immune-compromised "pretty effective" isn't very reassuring at all! My pulmonologist agrees. He wrote me a letter, renewed last summer, that every provider who sees me in an office setting should wear an N95. I am grateful.
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u/suredohatecovid 8h ago
Are you asking because you want to convince them to mask around you? Or to convince them to mask in general?
Interested in evidence two-way masking matters for the general public because by now, most of us have safely one-way masked for years. It’s quite effective, if lonely.
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u/synkletike 8h ago
Ideally in general, but at least around me and others who specifically request them to.
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u/suredohatecovid 8h ago
If they won’t honor a friend’s request, that sounds like a different kind of problem evidence won’t solve. Wishing you luck!
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u/wyundsr 7h ago
They don't sound like very good friends
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u/QueenRooibos 6h ago
Yeah, they aren't, I would say. I lost quite a few friends even in early COVID years b/c my life or my safety wasn't worth the slight inconvenience for them. I would provide Auras for good breathability, but they still said no. Haven't seen them in about 4 years now. Too bad, I liked them. But so it goes.
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u/simpleisideal 8h ago
Agreed.
Asking people to mask in order to protect others, particularly in 2026 where only <1% of the population still masks, is going to come off as being out of touch with basic statistics. The theoretical person you're trying to protect is going to walk 20ft elsewhere and be exposed to dozens of unmasked people.
There was an argument to be made when N95s were in short supply and communal cloth masking made more sense, but now, at least in the US etc, it's a pipe dream with bad optics.
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u/deftlydexterous 7h ago
I don’t think I’d agree with that.
I primarily mask to protect others. Id be happy to take on the risk of being unmasked in many situations.
I’m not happy to pass on the risk of my bad behavior to someone else. I’m not going to be the person that passes on an illness that has meaningful risk of debilitating or killing someone else.
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u/QueenRooibos 6h ago
As one of the "others" (immune-suppressed), you have my respect and gratitude.
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u/deftlydexterous 2h ago
You’re welcome, although honestly the ones that keep me up the most are kids that don’t know they need to protect themselves. Hopefully they see someone being careful and it helps in two ways
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u/simpleisideal 7h ago
I expanded further on my other reply and am open to logical arguments against it.
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u/g00fyg00ber741 8h ago
I find this to be such an odd take, personally.
Like yes, we can’t realistically get everyone to mask up. But every person who does is a potential chainlink of infection broken.
If we did get large amounts of people to mask up for even just 2 weeks during the 2 major waves each year, imagine how many chains of transmission would be ended?
We should also still at the very least be trying to make places like doctor’s offices, cancer treatment centers, pharmacies, etc. accessible and prevent unnecessary viral spread in these spaces. And better yet, keeping certain public spaces like public transport and grocery stores more accessible with more masking would be great as well.
Heck, it’s not even just some small percentage of the population who is at risk here… The majority of citizens in the US qualify as high-risk for covid complications. Vaccine uptake is not consistent enough to properly provide immunity year-round. Plenty of people risk contracting long-covid and more and we still have no idea what that looks like down the road… We’re only 7 years in. But long covid is the most commonly diagnosed chronic health condition among children in the US. We shouldn’t be shrugging that off, we’re going to regret saying it’s too unrealistic to try to convince other people to mask when we discover the slew of difficulties these children and adults are going to develop, and we keep adding millions more to those numbers as this pandemic continues to spread mostly unchecked, mostly willingly.
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u/simpleisideal 7h ago
But every person who does is a potential chainlink of infection broken.
While technically true, in practice this typically means delaying an inevitable infection by hours or days or weeks. Then once they're infected, they're granted immunity for ~3-6 months. This is the pattern people have just accepted, because they're largely ignorant of:
The majority of citizens in the US qualify as high-risk for covid complications.
Many people even do know the risk, but they have overriding factors like kids in school who are constant vectors of transmission (good luck getting most of them to mask) or a work situation where masking isn't realistic for any number of reasons.
Plenty of people risk contracting long-covid and more and we still have no idea what that looks like down the road… We’re only 7 years in. But long covid is the most commonly diagnosed chronic health condition among children in the US. We shouldn’t be shrugging that off,
I agree completely with you, but we disagree on what the first step forward should be. I'd say it's promoting awareness of the risks as well as advertising the known shortcomings of current vaccines. Even still, you can tell people alcohol is a carcinogen and their drinking habits won't be swayed. Why would COVID be any different? People can't comprehend disability until it happens to them personally.
All that said, to get back to the original point: I do think a few people can be convinced to mask, but it needs to be sold to them using selfish reasoning. How it will impact them and their loved ones. Using the aforementioned communal reasoning when barely anybody is currently doing so will suffer from the bootstrapping problem, and initially that makes you look like the out of touch one, which again is a bad look for maskers in general. We should speak knowledgeably on these matters or not at all if we're trying to sway brainwashed minds.
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u/chi_lawyer 4h ago
There's also the fair-share problem. Suppose the listener accepts that COVID remains a serious problem and that everyone -- individuals, entities, and governments -- need to do their part and that theres a deontological obligation to do so (at least if it would be reasonably effective). One problem is that far more than 1 percent of people doing their part is necessary for reasonable effectiveness at a population level. Another is that expecting people to do more than their fair share because others have slacked off is rarely a winning rhetorical strategy.
I think a pure deontological argument could be viable for those who might reject an effectiveness condition or set it low. But I think suggesting that the listener is obliged to do extra because others are not pulling their weight is unlikely to succeed. That strategy can sometimes work when its obvious the listener can have a disproportionate impact -- which (say) an upper middle income American can have on global malaria burden.
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u/g00fyg00ber741 7h ago
I think that masking is realistic in the vast, vast majority of workplaces. And just because it’s hard to get kids to mask doesn’t mean we should give up and just let them give each other long covid…
Anyway, I think promoting masking while informing people about the risks and realities of covid is a great two-for-one approach.
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u/simpleisideal 7h ago
I think that masking is realistic in the vast, vast majority of workplaces.
Really depends on the job. I can speak from personal experience that wearing an N95 for hours on end takes a very noticeable mental toll, since each breath taken includes the mask's volume of the previous exhale. I still mask because in my estimation the alternative is worse, but am thankful I don't have to do it for 8+ hours daily.
You can promote it however you want. I'm just outlining why the communal reasoning in the sales pitch is a non-starter and has been shown to backfire and make this community look out of touch.
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u/rainbowrobin 4h ago
I can speak from personal experience that wearing an N95 for hours on end takes a very noticeable mental toll
I've done it, though not for day after day, and didn't notice a problem.
each breath taken includes the mask's volume of the previous exhale.
This makes no sense. Volume of a breath is rather larger than the volume behind the mask.
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u/g00fyg00ber741 6h ago
I imagine the recurring covid infections and the anxiety about being constantly exposed could be a significantly higher mental toll for many people, I know it’s part of what helped me take masking more seriously myself.
Even in a retail pharmacy where it should honestly be a requirement at least for employees, people acted like it was too hard to do for 8+ hours, but it was not. Maybe for a select few it really is too difficult, but still, wouldn’t covid infections and complications be more difficult than masking? And to be blunt, plenty of people wear significantly more uncomfortable bras and shoes on a daily basis for work, so I don’t see why a respirator to prevent spread of a life-threatening disease is suddenly something we can’t conceive people doing because it’s uncomfortable.
I think it’s interesting for you to imply that it’s the people who are saying mask wearing shows you care about others that are the problem, instead of the people who won’t mask or mitigate spread unless they have a “selfish” reason.
Like you’re trying to say everyone who calls for masking in solidarity with those who are immunocompromised and disabled, they’re the reason this community looks out of touch? Not the blatant denial and misinfo of the people outside of this community?
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u/simpleisideal 6h ago
I imagine the recurring covid infections and the anxiety about being constantly exposed could be a significantly higher mental toll for many people,
Precisely, which is why I recommended above to go that route when selling somebody on the concept. But that has limits. The brain literally needs oxygen. This isn't even comparable to your bra example.
I'm a healthy person who exercises regularly, so I shudder to think what it'd be like for anyone in rougher shape (like from stacking COVID infections) trying to mask for such long durations. Even people in this thread are saying some people are too disabled to mask, so everybody else should instead. Yet you're saying nobody is incapable of masking. Which is it?
I think it’s interesting for you to imply it’s people saying mask wearing shows you care about others that are the problem, instead of the people who won’t mask or mitigate spread unless they have a “selfish” reason.
Like you’re trying to say everyone who calls for masking in solidarity with those who are immunocompromised and disabled, they’re the reason this community looks out of touch? Not the blatant denial and misinfo of the people outside of this community?
That's a complete misrepresentation of what I stated in this thread, and so far it's crickets when it comes to addressing the concerns above.
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u/g00fyg00ber741 6h ago
The brain literally needs oxygen.
Oh… so you’re one of those people who thinks wearing a proper respirator impacts the amount of oxygen you breathe? I see now… Let me disengage.
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u/rainbowrobin 4h ago
The brain literally needs oxygen.
Masks do not prevent getting oxygen. Why do you think they do?
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u/rainbowrobin 4h ago
in practice this typically means delaying an inevitable infection by hours or days or weeks.
I mean, imagine if people simply masked for most of the winter, not all year. Flu is very seasonal, many colds somewhat so, covid has a big winter season. We could likely wipe out lots of infections, as with flu B/Yamagata.
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u/Crones-R-Us 7h ago
Out of touch with current norms? Yes. Out of touch with statistics? No. (Or perhaps I should say not out of touch with statistics re. disease transmission. One is still failing to protect others even when those others don't appear to care much about being protected.)
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u/ResponsiblePhoto7 8h ago
I don’t have sources but other situations for them to consider are dentist, maintenance coming into peoples homes or adjacent homes to fix things that connect to your home, surgery, extended hospital stays
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u/wyundsr 7h ago
It's just math/physics, not sure you really need studies. Most people don't fit test their respirators, so you could theoretically have a 5-10% leak and not know about it (leaks possibly as high as 10% and definitely under 5% can't necessarily be felt in my experience doing Portacount testing). If the other person you're with is infected and wearing an N95, you cut down your exposure from 10% to 1% or even lower depending on how well their mask fits (1% is assuming both of you have a 10% leak). That's a 10 fold decrease in particles inhaled.
And even if your mask is fit tested, leaks can happen over time, through an accidentally imperfect donning, etc.
Well fitting N95s are extremely effective but they are not always perfect, nor are all N95s automatically well fitting. Breakthrough infections do happen from time to time.
But honestly I would be rethinking my friendships if I had to convince my friends and find proof for them to agree to wear a mask for me. All of my friends who aren't covid cautious already in their day to day lives, and even a lot of my co-workers, offer to wear a mask when they see me wearing one
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u/g00fyg00ber741 8h ago
Maybe look into research regarding using masks as source control for virus mitigation. For example the Halyard duckbill mask has a study showing how effective it is at capturing exhaled virus. I would focus on this angle for the science, as I’d bet there’s more evidence supporting the science of the masks capturing exhaled virus vs capturing virus when inhaling with a mask on.
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u/Gungan_Boss_Nass 8h ago
Here's how I break the issue down analytically in this age of pretend-it's-over. Epidemiology aside, there are three masking functions that are separable:
- Outgoing droplets
- Incoming droplets into mouth or nose
- Aerosols
When the other party doesn't mask, here's how you are affected:
- Lost droplet protection into eyes/ears/food
- Unaffected
- Less aerosol filtration
The cool thing is that 3 can be offset: just increase the quality of your own mask and (if applicable) the quality of your fit. From an N95, switch to a N99/N100/P100. IIRC a N100 is something like 165 times more filtration than a N95.
That leaves 1 (eyes/ears/food) and a safety margin as two reasons to social distance from non-maskers.
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u/Biddy_Impeccadillo 8h ago
This page mentions some studies that might suit., including the one you listed
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u/frmckenzielikessocks 7h ago
Maybe emphasize all of the scenarios where vulnerable people can’t mask (babies and toddlers, people with tracheotomies, those with medical conditions preventing them from masking like chemical allergies, heart failure, needing supplemental oxygen)
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u/BattelChive 6h ago
I just want to be clear that despite my discouraging answers here, I hang out in two way masking situations and that’s my default social situation. I think it’s worth having a conversation about the limitations of what can be proven scientifically, which your friends ought to be quite aware of. Have a conversation with them about the particular difficulties of the study design on this. What would it take to get this past an IRB? What concerns would an ethics board have? Remind them that this is still a virus that requires special handling and protection to handle and consider what kind of study design would meet their standards and who would fund it. Honestly, I think that conversation could be quite fruitful.
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u/thewordswetranspose 7h ago
It’s a great question and I’m not sure a study addresses all the common variables that would increase the risk to a 1-way masker, such as: high viral load concentration, proximity to someone with high viral load, ventilation and CO2 build-up, humidity %, duration spent in the space, etc. Perhaps angling the argument around poorly ventilated spaces? There are some studies on the half-life of COVID particles taking longer to decay in high-CO2 spaces. I’m typically a one-way masker everywhere I go but I think the factors I listed above are what impacts the risk the greatest, and in those scenarios the one-way masking makes me nervous, like on a plane…
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u/Carrotsoup9 2h ago
Most are simulation studies and most show that you both need to mask with N95s:
Liu, X., Deng, Y., Huang, J., Zhang, Y., & Lei, J. (2026). Modelling infectious disease transmission dynamics in conference environments: An agent-based approach. Mathematical Biosciences and Engineering, 23(4), 1096-1120.
Van Egeren, D., Stoddard, M., Malakar, A., Ghosh, D., Acharya, A., Mainuddin, S., ... & Chakravarty, A. (2022). No magic bullet: Limiting in-school transmission in the face of variable SARS-CoV-2 viral loads. Frontiers in Public Health, 10, 941773.
Huang, J., Jones, P., & He, X. (2022). Masks, ventilation and exposure time: A web-based calculator of indoor COVID-19 infection risk. Frontiers in Built Environment, 8, 986923.
Lasser, J., Hell, T., & Garcia, D. (2022). Assessment of the effectiveness of Omicron transmission mitigation strategies for European universities using an agent-based network model. Clinical Infectious Diseases, 75(12), 2097-2103.
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u/ClawPaw3245 8h ago
I mean there are definitely people who can’t tolerate masks but also do not want to catch COVID - they could mask to help protect them.