N95s are better, universal masking is better – and no, masks do not have a destruct sequence countdown, so whatever the time period, you’re at lower risk if wearing one than without.
This is a mask chart to demonstrate the relative improvement of both people wearing higher efficacy masks that other mask charts are trying to convey but which have been at times way way misunderstood with other mask chart infographics.
There are no arbitrary time limits or expiration.
Masks, including N95 respirators, work at their particular level of efficacy until they get clogged and difficult to breathe through, become wet, get soiled somehow, a strap breaks or loosens, or the mask wears out to the point it’s not making a good seal on the face anymore.
Is there a time limitation for wearing an N95 Filtering Facepiece Respirators? There is no time limit to wearing an N95. Respirators can be worn until they are dirty, damaged, or difficult to breathe through. To be effective, a respirator needs to be worn correctly and worn throughout the duration of the hazardous exposure. People using a respirator will need to go to an area with safe air to remove the respirator for any reason, including to eat and drink.
The Physics of N95 Masks.
N95 masks have filtration that uses layers and, as described in a MinutePhysics video:
The Astounding Physics of N95 Masks by MinutePhysics
“By electretizing the fibers in an N95 mask, they gain a long-lasting ability to attract particles, which means they capture about 10 times as many particles as regular fibers.”
This is also why if you leave your mask out in the open when you’re not using it, it could get clogged with dust sitting around – because it attracts particles and traps them. The physics hasn’t changed. And the only thing outdated about the MinutePhysics video is that N95s are no longer limited to expensive uncomfortable hardware store cup numbers, there are so many more options now.
Nowadays NIOSH approved N95 respirator masks, and other alternative respirator options, such as elastomerics, PAPRs, and KN95s, are widely available in a variety of more comfortable styles and price points.
And there are currently no shortages as of publishing this in December 2023.
Respiratory protection not limited to aerosol transmitted infectious disease.
Even before the pandemic, respirators have been used in a variety of settings for multiple types of respiratory protection such as painting, working in the presence of dust, exposure to allergens such as pollen, and for air pollution including wildfire smoke.
N95 respirators are very effective in reducing exposure to particulate matter pollutants like PM2.5. However, just as with COVID precautions, none of our precautions are perfect, so reducing exposure is important as well. This means reducing time spent outdoors. Today I skipped my dog walk.
Respirator masks are useful for mitigating airborne hazards, including respiratory viruses, and can be highly effective especially when used alongside vaccination, air filtration and ventilation, when avoiding the hazards is not feasible.
The mask chart misunderstandings.
These are some examples of the chart concept that’s been used in various iterations of a graphic meant to explain why one should upgrade their masking and how it’s better if both parties are masked, and with better masks.
The time periods on these charts are really meant to convey a sense of risk factor comparisons, and your odds of being infected given a certain length of exposure time in various levels of mask protection. There’s fine print on a chart stating that “The baseline of 15 minutes is not based on any science and could be shorter or longer, depending on the number of sources” – meaning that the time intervals on these charts are proxy concepts for calculating risk odds, but most don’t read the fine print, and even those who do seem to miss this aspect of the usage of time expressions.
Unfortunately there are several ways that people have misunderstood this graphic, and some ways the information presented is, albeit unintentionally, nevertheless misleading. If you already well understand aerosol transmission of respiratory disease, things may seem straightforward, but if you don’t already have an understanding of the physics of masks, and how airborne infectious disease spreads, as many in the general public still do not, it’s easy to misconstrue the concepts being presented in the mask charts.
The ways people misunderstand the charts:
People mistakenly believe that the time periods on the chart refer to an expiration date type time period, where after a certain time, the mask starts letting the virus through because the mask is degrading somehow, and will self-destruct or become degraded somehow.
- Someone posted on social media that in a particular situation they would do a time calculation based on the mask chart, assuming if everyone is masked while they were wearing an N95 since they’d be good for 25 hours, but if others weren’t masked they would step outside every hour and change their mask because of the 1 hour limit on the mask chart.
- The idea that you can reset the risk of exposure by just stepping outside, or replacing the mask is wrong. But it seems to make sense if you take the mask chart with the time frames at face value.
- Sometimes people think that the mask itself is degrading within that time period OR other times people think that you have to give the mask a rest because wearing it continuously is what’s causing the problem.
- When the people hear others are reusing their masks, this understandably causes more confusion, either reinforcing the misunderstanding, or they think people are in danger.
People mistakenly believe there’s some standardized infectious dose time for a virus, and that the mask slows that infectious dose time down by only letting in some virus, and as long as they only have a little bit of virus they won’t get sick, or that the mask will work reliably to entirely prevent infection up to that point, then stop.
- I’ve seen professionals quoted in news articles saying they’re not bothering to wear a mask if they’re “just running into the store for a few minutes” -possibly because that chart says 15 minutes to infectious dose with no masks on.
- You can infect or be infected within a few minutes. There have been instances where people have contracted covid with very brief exposure.
- Documented spread in Australia in 2021: CCTV captures ‘scarily fleeting’ encounter that resulted in Bondi COVID-19 cluster growing By Kathleen Calderwood – Mon 21 Jun 2021 – ABC News Premier Gladys Berejiklian added the encounter was “scarily fleeting”. “Literally people not even physically touching each other but fleetingly coming into the same airspace has seen the virus transfer from one person to another,” the Premier said. “That’s how contagious it is.”
- There’s fine print on a chart stating that “The baseline of 15 minutes is not based on any science and could be shorter or longer, depending on the number of sources…” but yet even professionals don’t seem to read that in the fine print, or recognize that the time intervals on these charts are proxy concepts for calculating risk odds.
- You can infect or be infected within a few minutes. There have been instances where people have contracted covid with very brief exposure.
- I’ve heard from people who believed since they’d have a brief one-on-one visit with someone, they would both be just as fine wearing surgical masks as N95s, if it’s under an hour, because that’s what the chart appears to claim.
- An N95 is always a better option than a surgical mask, no matter the length of time or what anybody else is wearing or not, because it’s just better.
- If one party is infectious, with both parties wearing masks, and especially with one person wearing a well fitted respirator, it could make a big difference whether it’s a 10 minute encounter or a 3 hour visit.
- All or nothing isn’t the right way to think about it since if neither party happens to be infected, then nobody would get sick no matter what the 2 people meeting wore. But there’s no way to know that for sure, even using testing is not foolproof.
- Better mask means better odds, and you don’t need time to infectious dose calculations to reason that.
People mistakenly think the chart’s binary of 2 people meeting up with each other applies no differently no matter how many people are present.
- The more people present in a place, unmasked, the greater the risk for all sorts of reasons including that it’s more likely that someone present is infected, it’s more likely that multiple people present are infectious thereby the infectious dose in the air will be higher.
- There are a lot of moving parts with infectious disease risk vectors, and that’s why there is no way to give people specific calculations for their risk. It’s just a matter of making things more likely to be safer, or less safe.
People mistakenly believe that if the chart says wearing a particular mask for 5 hours with an infectious person is effective, they think if they have to be in the room with someone who’s potentially infectious for 6 hours, they may as well not wear the mask at all at any point during the first 5 hours, because they’re going to get sick anyway in the 6th or 7th hour.
- A person asked someone how long would a fitted N95 one-way masking situation prevent covid spread and referred to the mask chart infographic that led them to believe that with one-way masking, if they have to be in the room for 16 hours they may as well not bother masking at all. The reason they were asking this is to find out if it was true with the current strains because the mask charts were from the year before — they just took it as a given that it’s not worth it to mask at all if they have to mask for more than 5 hours.
- This was never true with any strains because this isn’t how it works and it’s a misunderstanding inherent to the mask chart.
- The mask will keep working so long as it’s kept on consistently. It’s just that the longer someone is in a potential exposure situation, the more likely something can go wrong, or virus particles might make it past the mask, to the point where it infects the person.
- Someone incorrectly asserted on social media that the mask chart “proves” that school mask mandates were “utterly useless”, because almost all the kids wore cloth masks which only protected them for 26 minutes and the school day is 6-½ hours long.
- This is not how it works. Kids were better off with universal masking, even with cloth masks, likely because the source control reduced the amount of virus in the air in total, meaning that less filtration would still work to further limit the exposure. With nearly everyone unmasked, the dynamic is completely changed, and it becomes essential for the person seeking protection to have the best level of protection.
- Klein LM, Johnson SB, Anderson AC, Beharry K, Faden R, Guo X, Kallem M, Nicklin A, Regenberg A, Tariq A, Collins ME. Predictors of student mask mandate policies in United States school districts during the COVID-19 pandemic. Front Public Health. 2023 Jul 31;11:1217638. doi: 10.3389/fpubh.2023.1217638. PMID: 37583885; PMCID: PMC10423804. A recent study in Massachusetts, the only study so far investigating factors associated with school district decisions on mask mandates, found that school districts that lifted mask mandates experienced greater incidence of COVID-19 among students and staff compared to those that did not (4).
- Mask mandates in schools probably also had knock on effects like reminding people of how covid spreads and likely led to other pro-social mitigations like staying home when sick, testing, and surface cleaning.
People misunderstand the relevance of well-fitted or fit-tested respirator masks and think the chart means that fit tested masks don’t degrade as fast, or that the mask doesn’t work as well if it’s not gone through the process of fit-testing.
- Lots of people may have masks that would pass fit-testing, but since they’re not fit-testing, they don’t know it. That doesn’t change the fact that their respirator mask protection might be excellent.
- Fit testing is about testing, it doesn’t in itself change anything about the mask.
- The purpose of fit testing is to find out if a mask is definitely not making a good seal and is not working so well, so that adjustments can be made to the mask or to prompt someone to buy different masks to wear that are a better fit.
- Fit-testing is not an automatic guarantee or a sure thing, since fit can change, masks can shift, and seals can be broken by facial hair changes, or might slide from talking when one’s chin moves.
People mistakenly believe that anything less than the best N95 respirator masks are useless because the chart shows just how significantly inferior they are.
- All or nothing is not the right way to go about this. The perfect doesn’t need to be the enemy of the good. Any masking is better than no masking. More masking of any kind is better than less masking. People should be encouraged to wear the most effective mask they have access to and can afford, because even small to moderate reduction in risk might make a difference. This is where infectious dose may play a role.
- Efficacy of face masks against respiratory infectious diseases: a systematic review and network analysis of randomized-controlled trials 2021 Sep Eleven out of 16 RCTs that underwent a pairwise meta-analysis revealed a substantially lower infection risk in those donning medical face masks (MFMs) than those without face masks (RR 0.83 95% CI 0.71-0.96). Given the body of evidence through a systematic review and meta-analyses, our findings supported the protective benefits of MFMs in reducing respiratory transmissions, and the universal mask-wearing should be applied-especially during the COVID-19 pandemic.
The reasons these misunderstandings are bad for public health messaging:
- The chart’s misunderstandings feed into all or nothing fatalism propaganda.
- The time limits make it seem as if there’s no point in masking if you have to spend a lot of time somewhere anyway.
- The time limits give ammunition to anti-maskers who claim masks and mask requirements are bad based on using the misunderstanding of the charts to push their incorrect assertions.
- The focus on fit-testing, which is prohibitively expensive for many people, makes it seem like if you’re not high-tech fit-tested there’s no point in bothering, even though someone’s mask may fit great they just don’t know for sure because they haven’t fit-tested, and even a mask that would fail a fit-test is better than no mask at all.
- The mask charts needlessly “get into the weeds” with specific scientific concepts like efficacy and infectious dose.
- Most people don’t have time to become experts in infectious disease concepts, even if they want to.
- The average person just wants to know how to best protect themselves in a variety of situations.
- Trying to explain the concept of infectious dose in a simple graphic would be difficult – in the mask chart it’s obviously impossible to do it without introducing misunderstandings.
- There is a need to compare mask options, but having it expressed in terms of time confuses things needlessly, and if there’s some reason to use numbers to express relative risk, it’d probably be better to use some other arbitrary quantification with an unambiguous meaning specific to risk, and not interpretable as having another application.
- Getting into the weeds with infectious disease concepts when messaging the general public could have the opposite effect by implanting misunderstandings that will stick because of the halo effect.
- The chart sticks with a binary of 2 people meeting up with each other, and then people try to translate specific calculations based on that and apply it rigidly.
- People try to apply their “calculations” to both meeting up one on one with someone in their house and also apply it to large crowded gatherings, concerts, going to a banquet, etc.
- One of the most common settings where people are one-way masking for extended periods now is in workplaces with more than one other person, and often in a room with 50 people or more.
Feel free to quote or link to this page and to take my infographic to share. And please feel free to steal my ideas for your own messaging or graphics. If you are able to improve on this idea for an infographic on this topic, or have found other good graphics showing these concepts, I’d love to see them! Please let me know.
And this is probably one of the better infographics to demonstrate the benefits of universal masking versus one-way masking with an aerosol transmitted virus.
