12 ms·

Installing air filters in classrooms has surprisingly large educational benefits (2020)

308 points by tangjurine 2y ago

culopatin 2y ago
I wonder how smart I’d be if I didn’t sit in a classroom full of metal tables that got painted with such a thick layer of oil paint that it stunk of paint thinner until Spring
- LorenPechtel 2y ago
  Yeah, I got driven out of college by one bad building. (This was back before it was understood that a building can be a problem.) I simply couldn't think properly while in it. A problem with classes, a showstopper when the labs were in the building. I'm sure I would have flunked out if I had tried to take those classes. I have no idea what I was reacting to but there sure was something. (It felt a lot like one house where I had the same sense of something bad walking in the door--and long later a wall full of black mold was discovered.)
tangjurine 2y ago
>For a sense of scale, Mathematica Policy Research’s best evidence on the effectiveness of the highly touted KIPP charter school network finds that after three years at KIPP there is significant improvement on three out of four test metrics — up 0.25 standard deviations on one English test, 0.22 standard deviations on another, and 0.28 standard deviations on one of two math tests. I wasn't sure what .22 std deviations meant, so I looked stuff up a bit. For a normal distribution, going from the average to 1 standard deviation above is going from the 50th percentile to the 84th percentile. Going up .22 standard deviations from the average is going from the 50th percentile to about the 55th percentile.
fifteenforty 2y ago
Also, turns out preventing kids from getting sick improves educational outcomes.
- sheepscreek 2y ago
  My dad made a similar observation, assuming the children were young. However, upon reviewing the article, I noticed it doesn’t explicitly mention the grade level. Considering younger children have weaker immune systems, this could potentially lead to fewer missed classes and improved grades. Personally, my first grader misses out on a considerable number of classes. However, if these results were observed in grades 3 or higher, it could suggest a more substantial phenomenon. I randomly picked the third grade, but perhaps there’s a specific age after which the medical community considers a child’s immunity to be significantly enhanced.
  - fifteenforty 2y ago
    Ventilation and air purification have a strongly theoretical basis and there have been real-world studies showing a clear benefit. https://cleanaircrew.org/ https://cleanaircrew.org/ https://www.cleanairschools.com.au/ https://www.cleanairschools.com.au/
  - xwolfi 2y ago
    But then, what about being protected from sickness from a young age, to end up sick all the time as an adult ? You had a better education, we can agree, but your body got weaker as a result and now you can't be as productive as an adult. I exaggerate a bit, but I found that during covid, where the mask was mandatory in my place, I was never sick. The only few years in my life where I was actually healthy continuously for YEARS, I and my friends could not believe the impact of the mask. But then we were stuck at home, living in constant misery and stress. Once the masks disappeared, finally we could live again, and got extremely sick the first few years... Maybe a more normal balance would have been better ? Sick a bit continuously ? I think trying to avoid sickness is like trying to swim against the current, nature just works that way.
    - fifteenforty 2y ago
      I just keep wearing an N95. I've had maybe 3 infections in 5 years.
    - 2y ago
yimby2001 2y ago
[dead]
jwpapi 2y ago
Personal anecdote getting an airthings that reminds me to open the window (along with a pushover api setup) has probably been the biggest productivity improvement in 10 years.
- Cthulhu_ 2y ago
  It's kinda worrying you need an app / appliance to remember to open the window. Rule of thumb is to have the windows open at least 10 minutes a day, every day.
  - LorenPechtel 2y ago
    You realize a lot of us live in places where that would be very expensive? Not to mention that the HVAC plants are usually not sized with that in mind.
    - socksy 2y ago
      Why is opening the window expensive? Climate control?
      - willlma 2y ago
        Yep, it's cold outside. So there's a CO2, energy, comfort (choose two) tradeoff.
  - jwpapi 1y ago
    Sometimes I’m just too much in the zone working and I forget, leading to 10 mins more in the zone, but less overall focused work through the day.
rayiner 2y ago
Someone writes whether the data actually shows what it purports to show: https://statmodeling.stat.columbia.edu/2020/01/09/filters-benefits/ https://statmodeling.stat.columbia.edu/2020/01/09/filters-be... > The whole thing is driven by one data point and a linear trend which makes no theoretical sense in the context of the paper (from the abstract: “Air testing conducted inside schools during the leak (but before air filters were installed) showed no presence of natural gas pollutants, implying that the effectiveness of air filters came from removing common air pollutants”) but does serve to create a background trend to allow a big discontinuity with some statistical significance. I’m reminded of the walkback of scientific studies showing massive benefits from giving kids in third world countries deworming medications: https://www.theguardian.com/society/2015/jul/23/research-global-deworming-programmes https://www.theguardian.com/society/2015/jul/23/research-glo.... My beef with Matt Y.’s worldview of “scientifically driven public policy” is that the costs and benefits of public policy interventions are so devilishly difficult to study that you can’t meaningfully use them on realistic time scales to drive policy. This is an exceedingly simple hypothesis—filtering air improves test scores—that can easily be tested while controlling for confounding factors. But even then it’s hard!
- sudoshred 2y ago
  The material impacts associated with the recommendations a study makes can influence the results in a way that does not favor objectivity.
- Analemma_ 2y ago
  The study itself is pretty explicit that it is just one encouraging case study which the authors believe merits follow-up research, rather than something conclusive. Matt Y's reporting isn't as forthcoming about this as it probably should've been, but he does also say the same thing at the end. He sort of buried the lede but didn't lie or anything.
  - rayiner 2y ago
    I'm not accusing Matt Y. of lying. I like him and subscribe to his Substack. I'm just saying that the article illustrates the shortcoming of his approach to public policy. His data-driven approach to public policy is based on an overly optimistic view of reliability of the data.
knotimpressed 2y ago
Does anyone have any details on what kind of filter this was? I bought a relatively high-MERV filter for my home, but I’m wondering what I should actually be trying to filter out.
- Aurornis 2y ago
  The paper is here: https://edworkingpapers.com/sites/default/files/Gilraine_AirFilters_1.pdf https://edworkingpapers.com/sites/default/files/Gilraine_Air... I didn't see the model specified. They also said some schools got carbon filters, which is a different type of filter. There's footnote saying many filters weren't even installed because some teachers thought they made the air "too dry", which is major placebo effect at work (air purifiers don't extract moisture from the air). The entire paper is really not good quality, to be honest. You can get a small HEPA purifier for a single room to remove particulates. The size of the filter, noise level, and amount of air moved are things to look for. Stepping up to activated carbon would remove VOCs, but cost significantly more (see IQAir, Austin Air, but ignore the cheap models that don't have 10-20lbs or more of activated carbon).
- fifteenforty 2y ago
  Higher does not necessarily mean better. Higher grade filters filter more in each pass, but can overall provide worse performance as the air flow rate goes down. The air is being recirculated in a portable unit or in a standard domestic ducted heating/cooling situation.
- PaulKeeble 2y ago
  MERV 13's are optimal for particle removal because compared to a HEPA some of the removal requires multiple passes but the filters are a lot less restrictive and allow higher airflow. Corsi and Rosenthal looked into this with the CR box and came to the conclusion its technically faster at clearing a room than using HEPA standard filters. For infections and damaging PM2.5 particles mechanical filtration with MERV13 is the best you are going to get. You could also add potentially get a HEPA with a carbon filter which will get rid of volatile organic compounds which can also be damaging (but also just be the smell of food) but they don't tend to be as effective and depending on the mix of VOCs verses particles one filter may run out before the other and carbon really doesn't capture all that much or well. It is a good way to get rid of smell at least for a while. There is a whole world of different standards for filtration for industrial and hazard chemicals which the FFP2/3 and N95 standards for Personal Protective Equipment respirators will lead you into if you want to go into that rabbit hole, but for a household typically its mostlt about Particulate matter, Volatile organic compounds and CO2. CO2 is about bringing in fresh air from outside. Then when outside of the household N95/99 or FFP2/3 respitators do the same job in unclean air environments which is basically everywhere, outside or indoors in public places pretty much never meet the World Health Organisations levels for PM2.5 and often exceed CO2 (a proxy for re-breathing and a high change of viral infection spread) standards too.
Aurornis 2y ago
I'm all for installing air filters in classrooms for a number of reasons, but I also think the extreme results from this study aren't going to hold up to further research. From the paper: > To do so, I leverage a unique setting arising from the largest gas leak in United States history, whereby the offending gas company installed air filters in every classroom, office and common area for all schools within five miles of the leak (but not beyond). This variation allows me to compare student achievement in schools receiving air filters relative to those that did not using a spatial regression discontinuity design. In other words, the paper looked at test scores at different schools in different areas on different years and assumed that the only change was the air filters. Anyone who has worked with school kids knows that the variations between classes from year to year can be extreme, as can differences produced by different teachers or even school policies. Again, I think air filtration is great indoors, but expecting test scores to improve dramatically like this is not realistic. This feels like another extremely exaggerated health claim, like past claims made about fish oil supplements. Fish oil was briefly thought to have extreme positive health benefits from a number of very small studies like this, but as sample sizes became larger and studies became higher quality, most of the beneficial effects disappeared.
- xattt 2y ago
  If anything, schools able to implement air filtration and fresh air exchanges systems are likely those flush with cash and supportive parents.
  - xwolfi 2y ago
    And the resulting backlash 10 years down the line ? I don't think science should be used that way: who would trust it eventually ? Would you support a small study saying a medicine or a vaccine produces a 20 year life expectancy increase, all that to end up 20 years later with no improvement, everyone on that medicine, and the anti-everything yelling on every platform that the big pharma lobby poisoned our children ? Even when the studies are on large samples, double-blind, long time range with a clear explanation as to why there's an effect, we have people trying to kill the resulting health campaigns. Don't encourage fake ones !
hollerith 2y ago
Install air filters in classrooms in Los Angeles has. Places with clean outdoor air probably won't see much benefit.
- sebastiennight 2y ago
  Which begs the question. How many of those places are there, and how many large groups of humans with children would you believe live in such places?
PaulKeeble 2y ago
There have been some classroom studies in the UK showing a reduction in illness as well. They were a bit better run than this because they had some some pupils in filtered air and some not and even with the mixing at break time the reduction of illness met clinical significance. Given Covid is doing its thing all year around its quite an easy thing to do to drastically reduce the time teachers and pupils spend away from school and its a fairly easy measure to adopt. They do need to have the filters running however and that will involve explaining to the teachers how they work and why they are needed because in a lot of studies compliance has been a big issue usually due to misinformation rather than issues with the devices.
theoreticalmal 2y ago
Only marginally relevant, this is one reason I use swamp coolers in my home. My windows are open 24/7, 4 months of the year. I hear the birds in the morning and it’s so much more pleasant than shutting in an air conditioned box, in my opinion
- Mistletoe 2y ago
  Does the humidity not cause problems? What is the relative humidity in your home?
  - SoftTalker 2y ago
    I'd guess somewhere dry. Swamp coolers don't really work in humid climates.
  - IneffablePigeon 2y ago
    Unlikely to be a problem if the windows are open, in most climates.
- meroes 2y ago
  Do you not get massive amounts of dust?
  - mmooss 2y ago
    Why would opening the windows result in dust, except where there a lot of dust outside (near a construction site)?
    - bluGill 2y ago
      swamp coolers work - imples desert - implies dust
    - wahnfrieden 2y ago
      Having any roads/cars around is a major problem. Brake and tire dust. Many people live near roads and traffic.
yoshuaw 2y ago
A study published just yesterday [1] showed that just two airborne diseases [2] were responsible for approximately 85% of all sicks days in Greece during 2023-2024. Disregarding the common-sense argument that reducing collective suffering is a good thing overall - even by the cold hard logic of capital, being able to reduce company sick days by up to 85% is a huge opportunity. Imo we're way overdue standards and controls for clean indoor air that are on par with standards for drinking water and food. Like this article shows, we have the tech to provide clean air today. All we're missing is policy to uniformly deploy it. [1]: https://www.sciencedirect.com/science/article/abs/pii/S0196655325002846 https://www.sciencedirect.com/science/article/abs/pii/S01966... [2]: SARS-CoV-19: ~75% of sick days, Influenza: ~10% of sick days
- socksy 2y ago
  Might this be related to the fact that Greeks tend not to take sick days compared to other European countries[1]? Not coming to work because you have covid is far more culturally accepted (and maybe expected) than a common cold. [1]: https://www.ekathimerini.com/economy/1255154/greek-work-ethic-debunks-lazy-myth/ https://www.ekathimerini.com/economy/1255154/greek-work-ethi...
Balgair 2y ago
Anecdote: Our daycare was a plague ship right after covid 'ended'. None of the kids had any immunities, and they made up for it in a hurry. Man, what a terrible year. As a result, the daycare got a grant to get N-95 air filters installed and those UV lights that Chinese restaurants tend to have in the bathrooms. One per room. What. A. Difference. The infants and kids coming up are not nearly as sick, and when they do get sick, it's not nearly as terrible. The RSV vaccine has also been a godsend. I can't really tell/feel what what the silver bullet here, but the combinations have been amazing. So much so that we got them for the house.
- LorenPechtel 2y ago
  What lights are you talking about? UV capable of disinfecting isn't something you want to be looking at. (Are you perhaps thinking of the bug-zapper lamps that are sometimes described as UV? Way up at the top of the visual spectrum, a lot of bugs go for them. But they're just a lure to get the bug between the high voltage wires that actually kill it.) The only disinfecting UV lights I've heard of for use in occupied areas are hanging things that only point up where nobody's going to be exposed. I have heard of some research for safe UV lights that are high up in the UV, they actually still burn but without enough penetration to get through the dead skin layer.
- throwaway2037 2y ago
  Nice story. I can believe it. I was surprised that you mentioned the RSV vaccine. Last I checked, they were still working on it. I was wrong: There are three competitors now: (1) Arexvy (GSK), (2) Abrysvo (Pfizer), and (3) Mresvia (Moderna) Ref: https://en.wikipedia.org/wiki/Respiratory_syncytial_virus_vaccine https://en.wikipedia.org/wiki/Respiratory_syncytial_virus_va... Normally, I use this clinic in Thailand to compare prices for vaccines: https://www.thaitravelclinic.com/cost.html https://www.thaitravelclinic.com/cost.html The RSV vaccine is crazy expensive, even more than the HPV one. Over 200 USD is incredibly expensive in a developing country (like Thailand). > those UV lights that Chinese restaurants tend to have in the bathrooms I never heard of this. Does anyone have a link to one of these on Amazon or Alibaba? I am curious to learn more.
- HPsquared 2y ago
throwaway81523 2y ago
From 2020.
amluto 2y ago
I wish there was more data on the effects of gasses in the air on people. We seem to know: - Elevated CO2 in rooms impairs cognitive performance. - Elevated CO2 in submarines, at levels far higher than you would see in a normal room does not appear to impact cognitive performance. - Installing carbon filters (what this study actually looked at) might improve classroom performance. - People don’t like stuffy rooms. All this is consistent with multiple hypotheses. It could be that we just don’t know anything about it. Or maybe there is some gas or gasses emitted by people that isn’t CO2 that makes people mildly uncomfortable and have worse cognitive performance. CO2 is certainly a good proxy for ventilation quality in a space where air is exchanged with outdoors but where the gasses in the air are not otherwise changed. Carbon-filtered classrooms and submarines are not examples of this.
- jedc 2y ago
  (Former submariner here.) Elevated CO2 in submarines absolutely impairs performance. One example: there was a guy on my boat who got migraines when CO2 got too high - he was useless. Luckily the fix is simple - just turn on another CO2 scrubber. There's nothing special about a submarine that makes CO2 somehow different than anywhere else.
  - amluto 2y ago
    I recall this study and maybe another one: https://pubmed.ncbi.nlm.nih.gov/29789085/ https://pubmed.ncbi.nlm.nih.gov/29789085/ I’m definitely not an expert.
  - 4gotunameagain 2y ago
    What if you're low on sorbent and can't turn on another scrubber ? I wonder if sorbent quantity correlates with performance
- frognumber 2y ago
  CO2 is a proxy for many other gasses. Cheap CO2 sensors sense volatile organic compounds (VOCs), and use those to estimate CO2. Many of those gasses do impact cognitive performance. It's not obvious to me why CO2 would, but if CO2 is going up, so is everything else we breathe out. CO2 where I am is somewhere in the ≈400ppm-1000ppm range -- 0.04% or 0.1% -- and it's pretty inert. I'm not sure what harm it does. If it does to harm, rising CO2 levels should be much more concerning than "just" climate change. But I suspect it's other gasses.
acstorage 2y ago
Makes sense
deleted 2y ago
[deleted]
aetherspawn 2y ago
I’m so confused why they installed HEPA filters to filter out LNG and methane. And HEPA filters don’t really scrub CO2 that effectively, even with a carbon membrane, so can we really expect lower CO2 levels? Considering this, what’s the actual takeaway here? Cleaner air (dust/virus free?) is better for productivity? I am asking because I want to buy the same filter for work, but I am doubtful that the $700 HEPA filter sounds like the same filter they used, even though the article mentions they used readily accessible 5 stage filters.
- tangjurine 2y ago
  I'm guessing someone had a hunch and wanted to buy some HEPA filters. Also, all HEPA filters should filter air similarly, the price should be based on the rate at which air is filtered. I bought a HEPA air filter for $150 for my room.
  - sokoloff 2y ago
    There are ratings spanning H10, H11, H12, and H13 for HEPA filters.
- amluto 2y ago
  Having tried to dig into this a while ago, they installed carbon filters. Most of the stuff for sale as “carbon” filters has too little carbon to do much. You want quite a lot, and, for some gasses, you can get special impregnated carbon or other media.
  - aitchnyu 2y ago
    Tangential, are there DIY methods of activated carbon? I got pellets, impregnated sheets and a packaged one for my air purifier, but I dont know when they are helping and when they are exhausted.
    - schiffern 2y ago
      To tell when carbon filters are exhausted, the best way is to use an indoor VOC monitor. Air filter AC is specially prepared, so making your own DIY charcoal (while possible) isn't nearly as effective. You can mostly regenerate/desorb the carbon by heating it to 400F. Never use your regular oven though, not least of which because it reeks. Get a cheap toaster oven and disposable foil pans and do it outside, in a location where it can't possibly catch anything on fire.
dang 2y ago
Related. Others? A review of the effects of installing air filters in classrooms - https://news.ycombinator.com/item?id=22006595 https://news.ycombinator.com/item?id=22006595 - Jan 2020 (26 comments) Installing air filters in classrooms has large educational benefits? - https://news.ycombinator.com/item?id=22006033 https://news.ycombinator.com/item?id=22006033 - Jan 2020 (48 comments)
tehjoker 2y ago
Given that SARS2 affects cognition negatively, I would expect schools with universal air filtration to have larger improvements than we would have expected prior.
joeevans1000 2y ago
i'm sure it's because they were white noise generators essentially.
Animats 2y ago
What are they "filtering"? You can filter particulates, but methane removal is more complicated.
ribcage 2y ago
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aaron695 2y ago
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MemexXx 2y ago
Now let's see if the filters are not changed in a while, and how that effects the studies (not on purpose, I'm guessing that the upkeep is not very good with filters in general)
craigdalton 2y ago
There are well established hierarchies of evidence in health studies and this study would rank as low quality evidence due to inability to control for other factors. See https://gdt.gradepro.org/app/handbook/handbook.html#h.3183vuv3ey12 https://gdt.gradepro.org/app/handbook/handbook.html#h.3183vu... for background. In studies of pollution and impacts on health, the confounding factors often have a larger impact on the health outcome than the pollutant, such as particulate level, and therefore significant control of confounders is required to estimate any impact on the health outcome. The strong effect in this study is highly suggestive of a confounder rather than a real effect from particles or other pollutants and therefore would require a much better study design to support tacking action at a policy level with an expectation of a huge impact. Fine to put filters into improve overall air quality but just not with the benefit rationale suggested in this study.
amai 2y ago
Many air filters are generating annoying sounds. You get better air, but the distraction by the constant noise of the filter might be more than counter productive.
- brody_hamer 2y ago
  My first thought was the exact opposite. Ambient noise in classroom (from other students) can be very distracting, and I wonder if adding white noise helps kids to focus (in the same way that accoustic dampening would)

308 points by tangjurine 2y ago

I wonder how smart I’d be if I didn’t sit in a classroom full of metal tables that got painted with such a thick layer of oil paint that it stunk of paint thinner until Spring

LorenPechtel 2y ago
Yeah, I got driven out of college by one bad building. (This was back before it was understood that a building can be a problem.) I simply couldn't think properly while in it. A problem with classes, a showstopper when the labs were in the building. I'm sure I would have flunked out if I had tried to take those classes. I have no idea what I was reacting to but there sure was something. (It felt a lot like one house where I had the same sense of something bad walking in the door--and long later a wall full of black mold was discovered.)

tangjurine 2y ago

>For a sense of scale, Mathematica Policy Research’s best evidence on the effectiveness of the highly touted KIPP charter school network finds that after three years at KIPP there is significant improvement on three out of four test metrics — up 0.25 standard deviations on one English test, 0.22 standard deviations on another, and 0.28 standard deviations on one of two math tests. I wasn't sure what .22 std deviations meant, so I looked stuff up a bit. For a normal distribution, going from the average to 1 standard deviation above is going from the 50th percentile to the 84th percentile. Going up .22 standard deviations from the average is going from the 50th percentile to about the 55th percentile.

fifteenforty 2y ago

Also, turns out preventing kids from getting sick improves educational outcomes.

sheepscreek 2y ago
My dad made a similar observation, assuming the children were young. However, upon reviewing the article, I noticed it doesn’t explicitly mention the grade level. Considering younger children have weaker immune systems, this could potentially lead to fewer missed classes and improved grades. Personally, my first grader misses out on a considerable number of classes. However, if these results were observed in grades 3 or higher, it could suggest a more substantial phenomenon. I randomly picked the third grade, but perhaps there’s a specific age after which the medical community considers a child’s immunity to be significantly enhanced.
- fifteenforty 2y ago
  Ventilation and air purification have a strongly theoretical basis and there have been real-world studies showing a clear benefit. https://cleanaircrew.org/ https://cleanaircrew.org/ https://www.cleanairschools.com.au/ https://www.cleanairschools.com.au/
- xwolfi 2y ago
  But then, what about being protected from sickness from a young age, to end up sick all the time as an adult ? You had a better education, we can agree, but your body got weaker as a result and now you can't be as productive as an adult. I exaggerate a bit, but I found that during covid, where the mask was mandatory in my place, I was never sick. The only few years in my life where I was actually healthy continuously for YEARS, I and my friends could not believe the impact of the mask. But then we were stuck at home, living in constant misery and stress. Once the masks disappeared, finally we could live again, and got extremely sick the first few years... Maybe a more normal balance would have been better ? Sick a bit continuously ? I think trying to avoid sickness is like trying to swim against the current, nature just works that way.
  - fifteenforty 2y ago
    I just keep wearing an N95. I've had maybe 3 infections in 5 years.
  - 2y ago

yimby2001 2y ago

[dead]

jwpapi 2y ago

Personal anecdote getting an airthings that reminds me to open the window (along with a pushover api setup) has probably been the biggest productivity improvement in 10 years.

Cthulhu_ 2y ago
It's kinda worrying you need an app / appliance to remember to open the window. Rule of thumb is to have the windows open at least 10 minutes a day, every day.
- LorenPechtel 2y ago
  You realize a lot of us live in places where that would be very expensive? Not to mention that the HVAC plants are usually not sized with that in mind.
  - socksy 2y ago
    Why is opening the window expensive? Climate control?
    - willlma 2y ago
      Yep, it's cold outside. So there's a CO2, energy, comfort (choose two) tradeoff.
- jwpapi 1y ago
  Sometimes I’m just too much in the zone working and I forget, leading to 10 mins more in the zone, but less overall focused work through the day.

rayiner 2y ago

Someone writes whether the data actually shows what it purports to show: https://statmodeling.stat.columbia.edu/2020/01/09/filters-benefits/ https://statmodeling.stat.columbia.edu/2020/01/09/filters-be... > The whole thing is driven by one data point and a linear trend which makes no theoretical sense in the context of the paper (from the abstract: “Air testing conducted inside schools during the leak (but before air filters were installed) showed no presence of natural gas pollutants, implying that the effectiveness of air filters came from removing common air pollutants”) but does serve to create a background trend to allow a big discontinuity with some statistical significance. I’m reminded of the walkback of scientific studies showing massive benefits from giving kids in third world countries deworming medications: https://www.theguardian.com/society/2015/jul/23/research-global-deworming-programmes https://www.theguardian.com/society/2015/jul/23/research-glo.... My beef with Matt Y.’s worldview of “scientifically driven public policy” is that the costs and benefits of public policy interventions are so devilishly difficult to study that you can’t meaningfully use them on realistic time scales to drive policy. This is an exceedingly simple hypothesis—filtering air improves test scores—that can easily be tested while controlling for confounding factors. But even then it’s hard!

sudoshred 2y ago
The material impacts associated with the recommendations a study makes can influence the results in a way that does not favor objectivity.
Analemma_ 2y ago
The study itself is pretty explicit that it is just one encouraging case study which the authors believe merits follow-up research, rather than something conclusive. Matt Y's reporting isn't as forthcoming about this as it probably should've been, but he does also say the same thing at the end. He sort of buried the lede but didn't lie or anything.
- rayiner 2y ago
  I'm not accusing Matt Y. of lying. I like him and subscribe to his Substack. I'm just saying that the article illustrates the shortcoming of his approach to public policy. His data-driven approach to public policy is based on an overly optimistic view of reliability of the data.

knotimpressed 2y ago

Does anyone have any details on what kind of filter this was? I bought a relatively high-MERV filter for my home, but I’m wondering what I should actually be trying to filter out.

Aurornis 2y ago
The paper is here: https://edworkingpapers.com/sites/default/files/Gilraine_AirFilters_1.pdf https://edworkingpapers.com/sites/default/files/Gilraine_Air... I didn't see the model specified. They also said some schools got carbon filters, which is a different type of filter. There's footnote saying many filters weren't even installed because some teachers thought they made the air "too dry", which is major placebo effect at work (air purifiers don't extract moisture from the air). The entire paper is really not good quality, to be honest. You can get a small HEPA purifier for a single room to remove particulates. The size of the filter, noise level, and amount of air moved are things to look for. Stepping up to activated carbon would remove VOCs, but cost significantly more (see IQAir, Austin Air, but ignore the cheap models that don't have 10-20lbs or more of activated carbon).
fifteenforty 2y ago
Higher does not necessarily mean better. Higher grade filters filter more in each pass, but can overall provide worse performance as the air flow rate goes down. The air is being recirculated in a portable unit or in a standard domestic ducted heating/cooling situation.
PaulKeeble 2y ago
MERV 13's are optimal for particle removal because compared to a HEPA some of the removal requires multiple passes but the filters are a lot less restrictive and allow higher airflow. Corsi and Rosenthal looked into this with the CR box and came to the conclusion its technically faster at clearing a room than using HEPA standard filters. For infections and damaging PM2.5 particles mechanical filtration with MERV13 is the best you are going to get. You could also add potentially get a HEPA with a carbon filter which will get rid of volatile organic compounds which can also be damaging (but also just be the smell of food) but they don't tend to be as effective and depending on the mix of VOCs verses particles one filter may run out before the other and carbon really doesn't capture all that much or well. It is a good way to get rid of smell at least for a while. There is a whole world of different standards for filtration for industrial and hazard chemicals which the FFP2/3 and N95 standards for Personal Protective Equipment respirators will lead you into if you want to go into that rabbit hole, but for a household typically its mostlt about Particulate matter, Volatile organic compounds and CO2. CO2 is about bringing in fresh air from outside. Then when outside of the household N95/99 or FFP2/3 respitators do the same job in unclean air environments which is basically everywhere, outside or indoors in public places pretty much never meet the World Health Organisations levels for PM2.5 and often exceed CO2 (a proxy for re-breathing and a high change of viral infection spread) standards too.

Aurornis 2y ago

I'm all for installing air filters in classrooms for a number of reasons, but I also think the extreme results from this study aren't going to hold up to further research. From the paper: > To do so, I leverage a unique setting arising from the largest gas leak in United States history, whereby the offending gas company installed air filters in every classroom, office and common area for all schools within five miles of the leak (but not beyond). This variation allows me to compare student achievement in schools receiving air filters relative to those that did not using a spatial regression discontinuity design. In other words, the paper looked at test scores at different schools in different areas on different years and assumed that the only change was the air filters. Anyone who has worked with school kids knows that the variations between classes from year to year can be extreme, as can differences produced by different teachers or even school policies. Again, I think air filtration is great indoors, but expecting test scores to improve dramatically like this is not realistic. This feels like another extremely exaggerated health claim, like past claims made about fish oil supplements. Fish oil was briefly thought to have extreme positive health benefits from a number of very small studies like this, but as sample sizes became larger and studies became higher quality, most of the beneficial effects disappeared.

xattt 2y ago
If anything, schools able to implement air filtration and fresh air exchanges systems are likely those flush with cash and supportive parents.
- xwolfi 2y ago
  And the resulting backlash 10 years down the line ? I don't think science should be used that way: who would trust it eventually ? Would you support a small study saying a medicine or a vaccine produces a 20 year life expectancy increase, all that to end up 20 years later with no improvement, everyone on that medicine, and the anti-everything yelling on every platform that the big pharma lobby poisoned our children ? Even when the studies are on large samples, double-blind, long time range with a clear explanation as to why there's an effect, we have people trying to kill the resulting health campaigns. Don't encourage fake ones !

hollerith 2y ago

Install air filters in classrooms in Los Angeles has. Places with clean outdoor air probably won't see much benefit.

sebastiennight 2y ago
Which begs the question. How many of those places are there, and how many large groups of humans with children would you believe live in such places?

PaulKeeble 2y ago

There have been some classroom studies in the UK showing a reduction in illness as well. They were a bit better run than this because they had some some pupils in filtered air and some not and even with the mixing at break time the reduction of illness met clinical significance. Given Covid is doing its thing all year around its quite an easy thing to do to drastically reduce the time teachers and pupils spend away from school and its a fairly easy measure to adopt. They do need to have the filters running however and that will involve explaining to the teachers how they work and why they are needed because in a lot of studies compliance has been a big issue usually due to misinformation rather than issues with the devices.

theoreticalmal 2y ago

Only marginally relevant, this is one reason I use swamp coolers in my home. My windows are open 24/7, 4 months of the year. I hear the birds in the morning and it’s so much more pleasant than shutting in an air conditioned box, in my opinion

Mistletoe 2y ago
Does the humidity not cause problems? What is the relative humidity in your home?
- SoftTalker 2y ago
  I'd guess somewhere dry. Swamp coolers don't really work in humid climates.
- IneffablePigeon 2y ago
  Unlikely to be a problem if the windows are open, in most climates.
meroes 2y ago
Do you not get massive amounts of dust?
- mmooss 2y ago
  Why would opening the windows result in dust, except where there a lot of dust outside (near a construction site)?
  - bluGill 2y ago
    swamp coolers work - imples desert - implies dust
  - wahnfrieden 2y ago
    Having any roads/cars around is a major problem. Brake and tire dust. Many people live near roads and traffic.

yoshuaw 2y ago

A study published just yesterday [1] showed that just two airborne diseases [2] were responsible for approximately 85% of all sicks days in Greece during 2023-2024. Disregarding the common-sense argument that reducing collective suffering is a good thing overall - even by the cold hard logic of capital, being able to reduce company sick days by up to 85% is a huge opportunity. Imo we're way overdue standards and controls for clean indoor air that are on par with standards for drinking water and food. Like this article shows, we have the tech to provide clean air today. All we're missing is policy to uniformly deploy it. [1]: https://www.sciencedirect.com/science/article/abs/pii/S0196655325002846 https://www.sciencedirect.com/science/article/abs/pii/S01966... [2]: SARS-CoV-19: ~75% of sick days, Influenza: ~10% of sick days

socksy 2y ago
Might this be related to the fact that Greeks tend not to take sick days compared to other European countries[1]? Not coming to work because you have covid is far more culturally accepted (and maybe expected) than a common cold. [1]: https://www.ekathimerini.com/economy/1255154/greek-work-ethic-debunks-lazy-myth/ https://www.ekathimerini.com/economy/1255154/greek-work-ethi...

Balgair 2y ago

Anecdote: Our daycare was a plague ship right after covid 'ended'. None of the kids had any immunities, and they made up for it in a hurry. Man, what a terrible year. As a result, the daycare got a grant to get N-95 air filters installed and those UV lights that Chinese restaurants tend to have in the bathrooms. One per room. What. A. Difference. The infants and kids coming up are not nearly as sick, and when they do get sick, it's not nearly as terrible. The RSV vaccine has also been a godsend. I can't really tell/feel what what the silver bullet here, but the combinations have been amazing. So much so that we got them for the house.

LorenPechtel 2y ago
What lights are you talking about? UV capable of disinfecting isn't something you want to be looking at. (Are you perhaps thinking of the bug-zapper lamps that are sometimes described as UV? Way up at the top of the visual spectrum, a lot of bugs go for them. But they're just a lure to get the bug between the high voltage wires that actually kill it.) The only disinfecting UV lights I've heard of for use in occupied areas are hanging things that only point up where nobody's going to be exposed. I have heard of some research for safe UV lights that are high up in the UV, they actually still burn but without enough penetration to get through the dead skin layer.
throwaway2037 2y ago
Nice story. I can believe it. I was surprised that you mentioned the RSV vaccine. Last I checked, they were still working on it. I was wrong: There are three competitors now: (1) Arexvy (GSK), (2) Abrysvo (Pfizer), and (3) Mresvia (Moderna) Ref: https://en.wikipedia.org/wiki/Respiratory_syncytial_virus_vaccine https://en.wikipedia.org/wiki/Respiratory_syncytial_virus_va... Normally, I use this clinic in Thailand to compare prices for vaccines: https://www.thaitravelclinic.com/cost.html https://www.thaitravelclinic.com/cost.html The RSV vaccine is crazy expensive, even more than the HPV one. Over 200 USD is incredibly expensive in a developing country (like Thailand). > those UV lights that Chinese restaurants tend to have in the bathrooms I never heard of this. Does anyone have a link to one of these on Amazon or Alibaba? I am curious to learn more.
HPsquared 2y ago

throwaway81523 2y ago

From 2020.

amluto 2y ago

I wish there was more data on the effects of gasses in the air on people. We seem to know: - Elevated CO2 in rooms impairs cognitive performance. - Elevated CO2 in submarines, at levels far higher than you would see in a normal room does not appear to impact cognitive performance. - Installing carbon filters (what this study actually looked at) might improve classroom performance. - People don’t like stuffy rooms. All this is consistent with multiple hypotheses. It could be that we just don’t know anything about it. Or maybe there is some gas or gasses emitted by people that isn’t CO2 that makes people mildly uncomfortable and have worse cognitive performance. CO2 is certainly a good proxy for ventilation quality in a space where air is exchanged with outdoors but where the gasses in the air are not otherwise changed. Carbon-filtered classrooms and submarines are not examples of this.

jedc 2y ago
(Former submariner here.) Elevated CO2 in submarines absolutely impairs performance. One example: there was a guy on my boat who got migraines when CO2 got too high - he was useless. Luckily the fix is simple - just turn on another CO2 scrubber. There's nothing special about a submarine that makes CO2 somehow different than anywhere else.
- amluto 2y ago
  I recall this study and maybe another one: https://pubmed.ncbi.nlm.nih.gov/29789085/ https://pubmed.ncbi.nlm.nih.gov/29789085/ I’m definitely not an expert.
- 4gotunameagain 2y ago
  What if you're low on sorbent and can't turn on another scrubber ? I wonder if sorbent quantity correlates with performance
frognumber 2y ago
CO2 is a proxy for many other gasses. Cheap CO2 sensors sense volatile organic compounds (VOCs), and use those to estimate CO2. Many of those gasses do impact cognitive performance. It's not obvious to me why CO2 would, but if CO2 is going up, so is everything else we breathe out. CO2 where I am is somewhere in the ≈400ppm-1000ppm range -- 0.04% or 0.1% -- and it's pretty inert. I'm not sure what harm it does. If it does to harm, rising CO2 levels should be much more concerning than "just" climate change. But I suspect it's other gasses.

acstorage 2y ago

Makes sense

deleted 2y ago

[deleted]

aetherspawn 2y ago

I’m so confused why they installed HEPA filters to filter out LNG and methane. And HEPA filters don’t really scrub CO2 that effectively, even with a carbon membrane, so can we really expect lower CO2 levels? Considering this, what’s the actual takeaway here? Cleaner air (dust/virus free?) is better for productivity? I am asking because I want to buy the same filter for work, but I am doubtful that the $700 HEPA filter sounds like the same filter they used, even though the article mentions they used readily accessible 5 stage filters.

tangjurine 2y ago
I'm guessing someone had a hunch and wanted to buy some HEPA filters. Also, all HEPA filters should filter air similarly, the price should be based on the rate at which air is filtered. I bought a HEPA air filter for $150 for my room.
- sokoloff 2y ago
  There are ratings spanning H10, H11, H12, and H13 for HEPA filters.
amluto 2y ago
Having tried to dig into this a while ago, they installed carbon filters. Most of the stuff for sale as “carbon” filters has too little carbon to do much. You want quite a lot, and, for some gasses, you can get special impregnated carbon or other media.
- aitchnyu 2y ago
  Tangential, are there DIY methods of activated carbon? I got pellets, impregnated sheets and a packaged one for my air purifier, but I dont know when they are helping and when they are exhausted.
  - schiffern 2y ago
    To tell when carbon filters are exhausted, the best way is to use an indoor VOC monitor. Air filter AC is specially prepared, so making your own DIY charcoal (while possible) isn't nearly as effective. You can mostly regenerate/desorb the carbon by heating it to 400F. Never use your regular oven though, not least of which because it reeks. Get a cheap toaster oven and disposable foil pans and do it outside, in a location where it can't possibly catch anything on fire.

dang 2y ago

Related. Others? A review of the effects of installing air filters in classrooms - https://news.ycombinator.com/item?id=22006595 https://news.ycombinator.com/item?id=22006595 - Jan 2020 (26 comments) Installing air filters in classrooms has large educational benefits? - https://news.ycombinator.com/item?id=22006033 https://news.ycombinator.com/item?id=22006033 - Jan 2020 (48 comments)

tehjoker 2y ago

Given that SARS2 affects cognition negatively, I would expect schools with universal air filtration to have larger improvements than we would have expected prior.

joeevans1000 2y ago

i'm sure it's because they were white noise generators essentially.

Animats 2y ago

What are they "filtering"? You can filter particulates, but methane removal is more complicated.

ribcage 2y ago

[dead]

aaron695 2y ago

[dead]

MemexXx 2y ago

Now let's see if the filters are not changed in a while, and how that effects the studies (not on purpose, I'm guessing that the upkeep is not very good with filters in general)

craigdalton 2y ago

There are well established hierarchies of evidence in health studies and this study would rank as low quality evidence due to inability to control for other factors. See https://gdt.gradepro.org/app/handbook/handbook.html#h.3183vuv3ey12 https://gdt.gradepro.org/app/handbook/handbook.html#h.3183vu... for background. In studies of pollution and impacts on health, the confounding factors often have a larger impact on the health outcome than the pollutant, such as particulate level, and therefore significant control of confounders is required to estimate any impact on the health outcome. The strong effect in this study is highly suggestive of a confounder rather than a real effect from particles or other pollutants and therefore would require a much better study design to support tacking action at a policy level with an expectation of a huge impact. Fine to put filters into improve overall air quality but just not with the benefit rationale suggested in this study.

amai 2y ago

Many air filters are generating annoying sounds. You get better air, but the distraction by the constant noise of the filter might be more than counter productive.

brody_hamer 2y ago
My first thought was the exact opposite. Ambient noise in classroom (from other students) can be very distracting, and I wonder if adding white noise helps kids to focus (in the same way that accoustic dampening would)