I definitely feel like neither governmental policies or people's individual precautions and behaviours quite reflect that reality.
- We eat outside.
- We have filters upgraded to MERV-13 and the fans run the entire school day.
- We have windows and doors open on all classrooms, except for A) a few that don't open outside, or B) when it's rainy/windy to the point it's not possible. We have small, secondary HEPA filters that we run in those circumstances. (Often, we're blaring AC or heat into a room with all doors and windows open just to get a few degrees closer to comfort).
- We mask indoors, too.
So far, no secondary cases attributable to spread at school. We've had frequent testing for much of the time, too, so they'd likely get detected. Now a lot of the student body is vaccinated, too, but this dates to before that.
It seems to me like the ability to design a school like this would be the exception, not the rule.
Even just a single door open makes a big difference, IMO.
My ancient high school had 45-degree windows (for theft and suicide prevention I imagine). Why lock it all down? Cost?
If you can rely upon windows entirely for ventilation and thermal control, that's great.
Otherwise, windows that open leak more air when you don't want them to. They also let in more humid air, which in turn has a higher specific heat capacity and requires more energy to dry the air later. Their usage tends to be uneven, so you often have open windows while AC is also running elsewhere or in the same room, and this can upset air handling.
So, windows that open can paradoxically increase energy consumption in larger buildings.
Except … a pandemic! We are optimizing for the wrong thing IMO at the expense of simple practical, human driven comfort. Same reason we don’t have windows on the local trains anymore.
Practically for people in classrooms at random times, being able to open a window should be an option. Only central control of when the ventilation / heat is on just fails in so many situations.
I like having windows that will open in my classroom. But in the larger buildings with central, indoor hallways, the benefit of windows is smaller (much less outer surface area vs. volume of space) and the potential costs are higher.
Aside from pandemic-proofing, the main benefit I get is from having more ventilation when I do things that don't need to be under a hood, but still produce fumes/smoke. E.g. soldering.
Good modern buildings are being built with more ventilation and heat recovery built in. Taking this over windows that open can be a reasonable trade. Yes, on the pandemic axis, many of these buildings may be a little worse than a classroom with a whole long wall of opening windows.
The chief challenge is that of retrofits vs. new construction. Much of California's school infrastructure is 50--100 years old.
In general, newer buildings with sealed windows have pretty good air exchange (with heat recovery) and filtration.
> For much of the state, through much of the year, open windows are a reasonably minor consideration.
Yah, tell that to me languishing masked a 95 degree classroom between building heat gain and a temperature in the 90s, and now ending up with a 60 degree room. It's workable, but it sucks, and we're wasting a lot of energy just to maintain a few degree delta T from outside with open windows. We've had a few weeks where the open windows have been great, but a lot more crummy weeks.
I'm a little jealous of those upstairs in the high school building that don't need to open windows.... and have nice temperatures in their classrooms... and have also had 0 secondary COVID cases. It's also really hard to conduct class when there's music, PE, etc, activities outside.
> The chief challenge is that of retrofits vs. new construction.
I thought we were talking in the context of a new school building being built without windows that open.
That said, windows are nice. If you have a class full of kids that are restless, sometimes opening windows and getting some outside noise or a breeze through the room changes the entire mood. It would be sad to lose that.
(Keep in mind that mixing air also mixes infectious particles.)
A slight improvement is to have a single exit point (vented with a fan) and rely on structure permiability to introduce fresh air. That's effectively a negative-pressure system.
From there, exhaust and intake with heat recovery is the next obvious step.
I mention older construction as replacing building stock is a long-term and expensive process. New construction will account for an exceedingly small percentage of all utilised buildings. New construction currently planned or in process should if at all possible incorporate lessons from the COVID-19 pandemic, but that's a drop in the bucket. Retrofits are highly likely.
If you want to read further, I'm finding numerous results for a search on school ventilation in new construction and retrofits:
https://duckduckgo.com/?q=+school+retrofit+construction+vent...
Among the first of those, from the CDC:
Reoccupying a building during the COVID-19 pandemic should not, in most cases, require new building ventilation systems. However, ventilation system upgrades or improvements can increase the delivery of clean air and dilute potential contaminants. Consult experienced heating, ventilation, and air conditioning (HVAC) professionals when considering changes to HVAC systems and equipment. Buildings that provided healthy, code-compliant indoor air quality prior to the pandemic can be improved for pandemic occupancy using less costly interventions. Below is a list of ventilation interventions that can help reduce the concentration of virus particles in the air. They represent a list of “tools in the mitigation toolbox,” each of which can contribute towards a reduction in risk. Implementing multiple tools at the same time is consistent with CDC’s layered approach and will increase overall effectiveness of ventilation interventions. These ventilation interventions can reduce the risk of exposure to the virus and reduce the spread of disease, but they will not eliminate risk completely.
...
Open windows and doors, when weather conditions allow, to increase outdoor air flow. Do not open windows and doors if doing so poses a safety or health risk (e.g., risk of falling, triggering asthma symptoms) to occupants in the building. Even a slightly open window can introduce beneficial outdoor air.
https://www.cdc.gov/coronavirus/2019-ncov/community/ventilat...
That cites an industry study by ASHRAE (professional association):
https://www.ashrae.org/file%20library/technical%20resources/...
It also recommends on exhaust fans rather than interior circulation fans to minimise strong internal air currents, with intake provide as I've indicated above.
During a pandemic, it makes a lot of sense-- at least for the "extremes" of weather faced here.
> A window cracked open for ventilation, and either at the top of the classroom (warm weather w/ cooling active) or bottom (with heating), and a fan within the room for vertical mixing ... might help.
Might, but who knows how much? How does one weight the ordinary risk of sickness and infection (outside of a pandemic) with energy costs? (Especially when there are less energy-intensive ways to get the ventilation).
> A slight improvement is to have a single exit point (vented with a fan) and rely on structure permiability to introduce fresh air. That's effectively a negative-pressure system.
> From there, exhaust and intake with heat recovery is the next obvious step.
Yes, and pretty quickly from here you're ending up designing a structure without windows that open, so you can ensure that your fancy ventilation system does the right thing, filters don't get fouled, and you're not wasting heat.
> I mention older construction as replacing building stock is a long-term and expensive process.
Well, sure. But we were talking about it in the context of someone complaining a new building doesn't have windows. Older, smaller, poorly sealed buildings are a lot less likely to be retrofitted with no windows than new construction.
> It also recommends on exhaust fans rather than interior circulation fans to minimise strong internal air currents, with intake provide as I've indicated above.
Well, duh.
An otherwise well-sealed building, with a porous wall structure held at a small negative prssure, is effectively a very simple heat recovery ventilation system, too.
As for the energy to dry the air, I’m inexpert in this area¹ but under the impression dehumidification is essentially just a byproduct of how compressors work (the evaporator’s low temperature causes water vapour to condense) rather than something that takes deliberate effort—that, if anything, air conditioners are commonly now deliberately revapourising water to avoid dehumidification beyond the desired level.
—⁂—
¹ But I am trying to learn for part of a project of my own, a velomobile and trailer to be able to live out of indefinitely, where in the ideal case that I haven’t determined is feasible I’d really like it if I could have one compressor to drive food refrigeration, cabin cooling, heating a low-temperature slow-cooker-style oven, and providing my water supply.
OK, so I should add a little more nuance:
* With more water vapor in the air, the air has a little more heat capacity
* With more water vapor in the air, the temperature band for comfort is a little narrower
* With more water vapor in the air, air conditioners need to work extra hard to provide the same cooling.
That is, the more water there is in the air to begin with, the more will condense and return its heat of vaporization to the room.
On phase change energies: I don’t know enough to quantify things definitely there, but https://en.wikipedia.org/wiki/Latent_heat#Specific_latent_he... looks like the right thing, and suggests around 2.4kJ/g, which with water being as much as 5% of the air (100% humidity at 40°C) would be as much as cooling the air down by about another 0.12°C for removing all of it.
This is mostly for tall buildings though. For a school, it could be that they want to be able to control the airflow and AC. Having a window open could be letting out the heat causing the heating to work harder for no reason.
I would figure the first thing needed to answer that question is defining the "difficult-to-quantify" cost, right?
It's difficult to estimate. Of course, even with all this care, not everywhere is equally well ventilated. My room is wide open to the outside, but there are other rooms depending on central air and the room filter which may not be as well off. Trying to form policy on a room by room basis would be nutty.
> And is this benefit worth the difficult-to-quantify but very real cost of students being unable to see the faces of their classmates?
We do go outside quite a bit, and most students choose to not mask outside and thus see their classmates then. There's also the very real benefit of making many students-- and me, their teacher-- feel safer.
IMO the biggest cost is it's slightly harder to understand each other and we have a few more misunderstandings per day.
Further bounding the risk of me getting exposed by a student (ventilation + masking) lets me both see my elderly father and continue to teach. I don't financially need to teach, and as much as I find it rewarding, I'm not willing to take a large risk of killing family members to do it.
The hospitalizations tell the story, ie. we are doing better than under the big flu seasons from the past.
It's more that the majority thinks that masks work, so it won't change anytime soon.
I'm not "anti-mask". I'm just wondering whether we will see studies in 10-20 years about a bunch of children with lung problems from restricted airflow or weird fibers or chemicals, or other pathogens that grew on the masks, or something we haven't thought of yet.
Or who knows? Maybe kids will all have super strong lungs. Or maybe lucky ones will have stronger lungs and others will suffer. I just don't know.
Anyone studying this (potential) issue?
As far as I know, it was more of a fear than anything else. But it raises an important question: who controls the quality of the masks we wear? What's to stop a store from ordering substandard products and ordering all its employees to wear them?
* Adult vs child
* Material (e.g. cotton)
* Quality
* Wash / replacement schedule
* Activities performed
And while you're at it, consider that kids aren't dropping like flies from covid, either. So if you're performing a cost / benefit analysis, the cost to kids wearing masks doesn't need to be very high before it gets higher than whatever benefit the masks offer.
Outright death is rare, but there's quite a few pediatric hospitalizations. They likely come with long term consequences, too.
For that matter, influenza has been greatly reduced, and there's a lot of chronic sequelae to influenza infection in youth.
And don't forget to add secondary consequences. I'm still willing to teach them in part because of reduced risk to me and my father thanks to masking. And a slightly reduced chance of killing a parent or grandparent by bringing home COVID is notable, too.
But we’re talking about young kids here. Pre-school (age 2 - 4) is an especially critical time and early elementary is important too. This time is a short window in brain development when the brain is super elastic and learns many things. Much of language development isn’t just hearing and speaking, it’s also seeing the mouth movements. And this is the age when the brain learns how to recognize and display facial emotions. Is it possible by masking so much these young kids, we’re doing major damage to this learning process?
Maybe the answer is yes, or maybe it’s no. But no one is even considering this question. It’s just endless stupid debates about masking that doesn’t at all consider the special circumstances of this critical time in life, this short window when so much happens.
I.e. we fear the effects of total isolation of a four year old more than the risk of their stunted facial recognition practice etc etc
Elementary kids do not care one bit about wearing masks indoors. They picked up the habit quickly, don't complain, and now put the rest of us to shame. Indeed, they often don't bother (not out of fear, but just forgetting or not bothering) to remove when going outside.
And, the risk is much more significant than you imply, and the risk to us who work with them is substantial.
I'm looking forward to masks going away eventually for a lot of reasons (though I kinda hope they become normal for e.g. the worst month of flu season, like in many other parts of the world), but calling it abuse is just ridiculous.
Well I believe the opposite, and from having a teacher in the family I can tell you masks are INCREDIBLY detrimental to the educational experience. We're harming our children's education immensity by clinging to them.
> , the risk is much more significant than you imply
No it is not. It's not even a large enough risks in adults for the removals of freedom to have been justified, and there's MUCH, MUCH less in kids. The risk is virtually non-existent, not a worry whatsoever.
If you're still sitting here in 2021 and pushing for the continual suspension of freedom "for the children" over a near nonexistent worry, you are part of the problem.
OK. I'm teaching and doing fine. So are my colleagues.
Maybe. But, on the flipside:
* We spend a lot of time outside and unmasked
* Many teachers use clear masks during phonics instruction and other critical times
* Wearing masks makes parents more comfortable with sending their kids to school, and so is enabling more social contact.
There are also some ancillary / random benefits, too. A big fraction of kids spend a big fraction of time up to age 7 fairly hearing impaired from low grade ear infections and congestion, and we're finally getting classroom audio amplification out at scale, adding a few decibels to teacher voices that will be helpful in the long term.
Also one more random note: emphasizing looking at the mouth so much for emotional reading is a mostly Western thing and not universal in human cultures. I'm guessing we end up with a generation of kids that read the eyes much more.
Beyond curbing the spread of natural airborne diseases, it also may decrease the attack vector in our societies for airborne bio-terrorism/warfare.
And even beyond all that, we're becoming increasingly aware of how important clean air is for our overall health even without the risk of pathogens.
I could see it happening in new buildings, though. Possibly in existing buildings if an easy-to-read summary number for ventilation became popular and the numbers for specific spaces became easy to find and widely publicized. Then companies might be willing to pay more to rent space with a higher "ventilation score", especially if employees balked at working in spaces with low scores.
What means it's probably useless against any airbone virus. But it's pretty great against particle pollution, in case you want to use it in a private space.
Just in case smaller particles have a substantial role, I quoted the 1um number.
The wealthy and the high income earners will start avoiding buildings, businesses, and organizations that won't or can't sufficiently upgrade to be considered safe. Their money will flow and support the healthy/safe alternatives.
Those that are left behind will be the dregs that the poor and desperate use and will gradually fall into disrepair until their owners go bankrupt or give up and sell to someone who has the means and drive to upgrade or demolish and rebuild.
The same thing happens to any old infrastructure where people can vote with their feet.
I think the challenge with indoor air circulation is the energy required to do so, especially when heating/cooling of the air is involved.
But, I'd sure love better indoor air quality.
Sounds extremely far-fetched. Any terrorist attack will be designed with the countermeasures in mind. Deploying enough biological agent to swamp the ventilation system would likely not be an issue.
I speculate this fact -after- a someone actually did fly their airplane into our building. The pilot received exceptionally bad customer service from us and was attempting to kill one of our leaders.
The meter was one of the best investments I ever made.
If it is, it's probably far overwhelmed by the shear weight of more well educated people and better tools at our disposal.
Yes, longer exposure time increases infection probability, but the 15 min threshold is arbitrary, like the 2 meter social distancing.
A bit like the "you can pick up food from the floor if it sat there for less than 5 seconds" meme.
Source: https://www.abc.net.au/news/2021-06-22/covid19-cctv-footage-...
Were these single-digit infections all symptomatic, or were they detecting asymptomatic infections too? What is the false positive and false negative rate of the type of testing Australia is doing, and how many people were being tested during this time?
If some of the infections were asymptomatic, is it possible that some of them are false positives, and the fleeting encounter was also a false positive (either a false positive test, or that wasn't the true source of the infection) just due to random chance?
In that period 30k-60k people where being tested in NSW. https://www.covid19data.com.au/nsw
In answer to your final question - no - they were PCR confirmed cases. There was also a high degree of sequencing occurring to enable clarity on lineage transmission
One of the infections was traced to a department store and the interaction between the two people was caught on cctv. They walked past each other and didn't talk. It was seconds.
* A vast majority of infections can be traced
* You have an infection whose only traceable contact is for a few seconds in a store...
It seems pretty likely that the infection happened in the moments surrounding those few seconds. Especially when we have multiple circumstances like this. Especially when it agrees with our underlying understanding of the germ theory of disease.
Extended contact makes infection much more likely. But people who are sick shed live virus, and there's not a safe level of exposure of live virus where infection is impossible.
This becomes an unlikely explanation once
> > * A vast majority of infections can be traced
and
> > Especially when we have multiple circumstances like this.
The probability of an alternate explanation becomes exceptionally unlikely. It's further reduced by our general scientific understanding that:
> > But people who are sick shed live virus, and there's not a safe level of exposure of live virus where infection is impossible.
Infection from a momentary contact is fairly unlikely. But when you have a massive number of momentary contacts in the populace, it happening many times becomes a near certainty.
E.g., this:
> Several individuals in Australia were also infected with the Kappa variant through lingering virus aerosol particles in the hallway of a quarantine hotel in May. Though the individuals had no direct contact with each other they opened the doors to their hotel rooms within 30 minutes of each other and tested positive for the same strain.
No complete sequencing, but the same variant... spread several times apparently by the same mechanism of indirect contact, several individuals infected. In a quarantine hotel, where there's not many alternate explanations available.
Or this one, confirmed by sequencing:
> A similar event occurred earlier in April where two families quarantining in rooms next to one another were found to share the same viral sequence, after briefly opening their doors 30 minutes apart.
https://www.forbes.com/sites/williamhaseltine/2021/06/28/inf...
Arbitrary guidelines are chosen:
- Because at the population level they're likely to be effective. Yes, individuals may get sick. Or die. But with the measures in place, overall risk and impacts should be reduced.
- They're actionable, memorable, and can be monitored and observed. Masking, hand-washing, limited exposures, limited occupancy, maintaining distance --- these all help reduce transmission, they're simple guidelines most people, even young children, should be able to comply with, and they can be readily and visibly observed.
It's a balance of benefits, risks, adoption, and enforcement.
Immunity status is harder to assure and measure, but vaccination standardises the innoculation, creates a memorialisable event, and can be checked if needed at specific locations and junctures.
The "five second rule" is far less meaningful than what's on the floor. But if you happen to see something fall, note that where it landed was reasonably clean, and if possible can wash it ... you're likely to make a better assessment than if it's been sitting for a few days. Even then, I'd make a sharp distinction between five seconds on my bedroom floor, vs. in the bath, or in a public building or street.
That said, much food comes from the ground. Wash and prepare suitably, you're reasonably safe.
Why? I honestly don't know. It isn't lack of wanting to be safer. But it has gotten fatiguing to try to keep up with what makes us safer today. I remember the start when folks wiped down delivered groceries. Even isolated them for a few days. Nowadays, it seems masking is still the visible thing to do, but most seem pretty sure that it is the vaccination that will make a difference. Anything else is a slowdown, at best.
What wasn't tested (or detected) were the times when you were asymptommatic but still infected with one the many influenza variants.
English is a little problematic when it comes to describing infectious disease. In all cases, there is the disease agent (e.g. an influenza virus) and there are the disease symptoms (e.g. "flu"). But we tend to say "I had the flu" without it being clear if we mean "the disease agent was present" or "i had the symptoms".
So yes, almost all of us are going to be exposed to SARS-COV-2 at some point. Slowdowns are doubleplus good because the biggest risk from the disease is related to its impact on public health care systems rather than serious illness or death at the individual level. Masks slow down transmission, vaccination reduces chance of required hospitalization.
I am open to the argument. Just feels to be begging a lot of other questions.
And note that R0 can be changed by altering some environmental factors in the formula above.
(1) likelihood of death decreases with the passing of time, because of improved treatment (and maybe testing also). So to minimize death, you want your exposure to be delayed as long as possible.
(2) there is reasonably convincing evidence that exposure level is significant in determining severity post-infection. Therefore you want to live within a community and with habits that keep you away from high exposure as much as possible.
So, the same strategies that slowdown exposure also help to reduce deaths
That said, your first point is a good one. If made difficult by how many later waves in most places have similar death peaks to earlier ones.
I still think we are far away from really having evidence on any good strategy, sadly. All of the places that had it under control seem to have lost said control.
Which, ultimately, is a good enough argument for me, to not just give up on things that have any chance of helping. Sucks, as I am clearly open to the arguments that deniers use. Which... I'm not trying to further that angle, either.
I still isolate groceries for at least 6 hours, delivered or not. Still clean my hands or wear a glove when I touch something outside.
I haven't got sick since Covid appeared. I used to have pretty severe nasal allergies (or so doctors told me) at least once a month, I haven't had one episode since early 2020. This is a life-changer for me.
Same thing for the usual minor health issues such as cold, cough, sore throat. All gone.
So I keep my Covid routine, probably even if Covid goes away, it's not that much of an effort and the results have been spectacular.
For me, I also saw that we had fewer sicknesses when the kids were all home schooled. Not shocking, we got a ton of bugs when they started school back. Not sure how sustainable it is to have such isolated lives, though. :(
Correct. Being a software developer helps immensely.
The only thing I do is that I wash my hands every time I return from public, as I always have been. I haven't gotten sick either.
There were numerous diseases that it's now clear probably had a very strong airborn-transmission component. Some we know of and their potential for transmission is extreme, e.g., smallpox. Turberculosis transmission all but certainly benefitted from cramped living, working, and travel conditions. Legionaire's disease was discovered in the 1970s, thriving in the cool, moist, air-conditioning ducts of a hotel (and affecting a convention of the American Legion, hence the name).
"Seasonal" cold and flu are also all but certaily amplified by indoor living, working, shopping, and related activities. The impact of COVID-19 countermeasures in reducing their prevalence over the past two years has been profound.
"Sick buildings" have been an issue since the 1970s (largely following increased energy-efficiency measures reducing air circulation), and there seem to be multiple components including chemicals in structural, decorative, and celaning/other materials. I predicted early into the Covid pandemic that changes to building construction, operations, and HVAC systems would likely be a lasting legacy of this pandemic.
https://www.medrxiv.org/content/10.1101/2020.03.30.20047217v...
CONCLUSIONS Most included trials had poor design, reporting and sparse events. There was insufficient evidence to provide a recommendation on the use of facial barriers without other measures. We found insufficient evidence for a difference between surgical masks and N95 respirators and limited evidence to support effectiveness of quarantine. Based on observational evidence from the previous SARS epidemic included in the previous version of our Cochrane review we recommend the use of masks combined with other measures.
Given that there is indeed a mask shortage and that medical workers absolutely do need these masks more, what should the authorities have said? The full painful truth. Despite warnings from experts for decades, especially after the near miss of SARS, we still weren’t prepared for this pandemic, and we did not ramp up domestic production when we could, and now there’s a mask shortage — and that’s disastrous because our front line health care workers deserve the best protection. Besides, if they fall ill, we will all be doomed.
If anything, a call for people who hoarded masks to donate some of them to their local medical workers would probably work better than telling people that they don’t need them or that they won’t manage to make them work. “Look, more masks would be great. We are doing our best to ramp up production. Till then, if our medical workers fall ill, we will all be worse off. Please donate any excess — maybe more than two weeks’ worth per person — to your hospital” sounds corny, but it’s the truth.
https://www.nytimes.com/2020/03/17/opinion/coronavirus-face-...
Oddly, it seems to be those who still most strongly resist wearing (or bully others for wearing) masks who seem to recall those first few weeks of ill-advised messaging.
The Bangladesh study is a particularly good one, demonstrating changes in disease prevalence even with less than half the population following masking recommendations: https://ncrc.jhsph.edu/research/the-impact-of-community-mask...
Mask makes great sense in specific contexts. Near vulnerable groups. In tight spaces and areas of low ventilation. In areas where a large number of people meet. The further away from such areas, the less evidence we get.
There is a reason why conferences is generally associated with people getting sick, while the same can't be said about the beach.
The Bangladesh study is likely informative in busy grocery stores, retail, offices, schools, etc.; certainly more than just "inside small huts".
The study did not show that. It was a study conducted in rural areas of Bangladesh, areas with small villages of huts and some mosque. Those are quite different from a large city mall and office complex. Schools are a even more complex since while children has a significant higher rate of getting sick in general, the transmission rate between children and adults is significant lower. The ruling on school lock downs and mask in schools has yet to be established.
We can look at specific examples. If you are on a packed plane then a mask is pretty good idea. Traveling on a bike then it is unlikely to do anything good. Mask in crowded open floor plan with bad ventilation, yes. Mask in personalized offices with good ventilation, no. A conferences, yes. A school, maybe. A bench, no. A large grocery store in off-hours, less likely. A crowded grocery store in rush hours, more likely. In a public bath house, the data seems to indicate no.
Things that seems to correlate with transmission rates seems to primarily be about: distance between people, ventilation and humidity, practicality of staying isolated at symptoms, age and risk groups. Raise any attribute of those to an extreme and one can get data that either prove or disprove masks as effective.
Our review of the literature offers evidence in favor of widespread mask use as source control to reduce community transmission: Nonmedical masks use materials that obstruct particles of the necessary size; people are most infectious in the initial period postinfection, where it is common to have few or no symptoms (45, 46, 141); nonmedical masks have been effective in reducing transmission of respiratory viruses; and places and time periods where mask usage is required or widespread have shown substantially lower community transmission.
The available evidence suggests that near-universal adoption of nonmedical masks when out in public, in combination with complementary public health measures, could successfully reduce Re to below 1, thereby reducing community spread if such measures are sustained.