9 ms·

The Weight of Numbers: Air Pollution and PM2.5

117 points by anarbadalov 8y ago

anarbadalov 8y ago
Undark & the Pulitzer Center visited seven countries on five continents to examine the impacts of particulate pollution on the lives of everyday people, and to uncover what’s being done — or not — to address it. The project is comprised of data visualizations, short narratives, on-the-ground 360-degree videos, an explainer film, and photos from Pulitzer prizewinning photographer Larry Price. What's interesting is that PM2.5 is a measurement used by policymakers and organizations all over the world, yet the average person doesn't really know what it is, or why it matters. (I know I didn't until we began work on the project.) And it turns out that while developing nations bear the brunt of it, this kind of pollution doesn't discriminate, and it's a problem everywhere from India to Nigeria to California. In fact, a full 90% of people live in areas that exceed World Health Organization guidelines for exposure, so the odds are high that wherever you live, you’re breathing it in, too. [full disclosure: I work for Undark. We're a non-profit science and society magazine published under the auspices of the Knight Science Journalism program]
- sberder 8y ago
  A very interesting subject indeed, living in China and running a startup in that field, I find educating people is the biggest challenge of all!
- ggm 8y ago
  Do you work with the people at QUT (Brisbane) or Floreanopolis (Brazil) doing fine particulate work near airports and in hospitals? my partner did some proofreading and english-as-a-second-language with these people, fascinating stuff (as a complete outsider) and very important.
  - anarbadalov 8y ago
    We don't. While we do often publish stories on public health issues, we don't conduct any of the research, we just report on the science. Australia and Brazil aren't regions we visited for this project, although I wouldn't be surprised to hear that there are areas experiencing extreme events in both.
    - ggm 8y ago
      Australia has a huge depndency on air and road freight with massive diesel subsidy to truckers and more air miles per Citizen than many other economies. We also have long hot dry weather. So the fine particulate matter issue here. Brazil has inadequate health funding and high humidity so gets mould..
gh02t 8y ago
I recently built a sensor for particulate matter (using the Plantower PMS7003, a laser-based sensor) and it's interesting to look at the effects of every day tasks. Cooking for instance causes a huge spike in PM1.0/2.5/10.0 levels, but so do more mundane tasks like vacuuming or spraying aerosols. I'd like to add a sensor for CO2, but it's a bit more complicated. A lot of the easy to use sensors marketed for the purpose are MOX sensors and the "equivalent CO2" reading they give is pretty much a complete lie except in a very narrow range of circumstances.
- legulere 8y ago
  I have a sensor built into an air purifier and have observed the same. Anything textile-related is bad like shaking out your blanket, which makes carpets seem horrible to me. But frying stuff really is the worst. You can go in the hundreds of micrograms, even with induction. A positive thing I have also learned is that opening the windows works best to get PM levels to a background level. Luckily it is only in the area of 5-20ug pm2.5 here For CO2 i have been recommended this one: https://clientmedia.trade-server.net/1768_tfadost/media/8/00/1800.pdf https://clientmedia.trade-server.net/1768_tfadost/media/8/00... which seems to measure CO2 directly.
  - qiqing 8y ago
    Do you recommend the air purifier that you have? And would you mind sharing which one has a built-in sensor? I'd like to try measuring my laundry room.
    - sberder 8y ago
      Most purifiers on the market with built-in sensors are unreliable to measure. They usually go for cheap IR sensors without flow control. Your results will vary wildly depending on conditions (temperature and humidity affect measurements a lot). I personally like Xiaomi purifiers for their affordability and noise level. If you're concerned about measuring pm2.5 in your space, you should consider buying a good entry level monitor like the laser egg or air visual (acquired by iqair not so long ago). Don't hesitate to ask more questions, air quality had been my main business for the past 4 years.
elektor 8y ago
Does anyone have experience with buying an air quality sensor for personal use? I know of Plume and AirBeam but have not seen them in use.
- rahimnathwani 8y ago
  A popular one among expats where I live (Beijing) is the Laser Egg.
- jonathankoren 8y ago
  I have a https://www.purpleair.com/ https://www.purpleair.com/ . It measures PM 1.0, PM 2.5, and PM 10.0 . It uses the same laser scanning sensor that everyone else seems to be using, a https://learn.adafruit.com/pm25-air-quality-sensor/overview https://learn.adafruit.com/pm25-air-quality-sensor/overview , only it has two of them. You have to plug it into the wall and it communicates over wifi. Honestly, it feels a bit mom-and-pop-ish (it's literally housed in a PVC pipe.), but it seems to work. Purple Air, talks about how it uploads everything to PurpleAir.com, but their website is really really janky. Luckily, the device has a web server, and spits out data in JSON, so even if Purple Air goes belly up, your sensor should still work. I have mine integrated into http://www.weewx.com/ http://www.weewx.com/ via https://github.com/bakerkj/weewx-purpleair https://github.com/bakerkj/weewx-purpleair , and I calculate an Air Quality Index from this data using https://github.com/jonathankoren/weewx-aqi https://github.com/jonathankoren/weewx-aqi . Ideally, I'd like a sensor that calculated all the other pollutants you're supposed to track, but this is what I have. The sensor is responsive. When the smoke filtered down from the Mendocino Complex fire last week, I saw a huge spike across the particulates, and even today with the Spare The Air alert, the AQI is quite a bit elevated. The one thing I'll note about its performance, is that after installation, the sensor read abnormally high until the first rain. After that, its performance is on par with other surrounding sensors. Would I recommend it? I don't know. I feel like I should have shopped around more for one, so I can't really compare it to anything. I do like how it reports data in an open manner.
- oh_sigh 8y ago
  I have this one and it works quite well: https://www.amazon.com/gp/product/B071RF6B2Y https://www.amazon.com/gp/product/B071RF6B2Y I compared it with a friends much more expensive device, and the results were within 5% of each other.
clumsysmurf 8y ago
Its probably worse that it looks "Researchers from Queen Mary University of London have found that people exposed to air pollution levels well within UK guidelines have changes in the structure of the heart, similar to those seen in the early stages of heart failure." https://www.sciencedaily.com/releases/2018/08/180803103315.htm https://www.sciencedaily.com/releases/2018/08/180803103315.h...
- graeme 8y ago
  >In the study, average annual exposures to PM2.5 were well within UK guidelines (25µg per cubic metre), although they were approaching or past World Health Organisation (WHO) guidelines (10µg per cubic metre). What AQI do these numbers translate to?
- sundvor 8y ago
  That's interesting. We're looking at moving our son to a new school that's right at the corner of two major artery roads in Melbourne, with some 17 000 vehicles passing daily (just on one of them) according to VicRoads. The building doesn't appear to have a HVAC/filtration system. Playground is behind the building, but still has significant back traffic and is inside of 100-300 metres from the main roads. I'm saying that the fumes from the cars and trucks could likely have long term health impact, but struggling to convince wife of this - she says if it was that dangerous, then why wouldn't someone have done something about it? I must clearly be paranoid.. ? Personally, even though the small school appears otherwise excellent, I'm loath to expose him to these fumes. I seem to have acquired an ability to taste them whilst on my bicycle commute, and will don a Respro mask when riding the streets with the most backed up traffic.
  - clumsysmurf 8y ago
    You have a legitimate concern, I've seen a few studies over the years measure VOCs as a function of distance from busy roads. Here is a very recent one: https://www.sciencedaily.com/releases/2015/04/150421105344.htm https://www.sciencedaily.com/releases/2015/04/150421105344.h... https://futurism.com/an-app-can-identify-highly-polluted-areas-in-cities/ https://futurism.com/an-app-can-identify-highly-polluted-are...
mikeyouse 8y ago
Does anyone have a sense of where the damage is done regarding PM? I live in SF and our apartment is a block away from a busy road and a gas station, both of which concern me. Not to mention the wild fires of late depositing ash all over our yard.. Also, being a SF apartment, there isn't A/C so we leave the windows open on hot days. Is there data around whether an active air filter running in a closed room before we go to sleep will help? Should it just run constantly? Is there any good method to actually lower the amount of PM I'm inhaling?
- cyrildorsaz 8y ago
  I bought a AirMega last year. It always runs on "quiet mode" and the PM2.5 is below 5 all the time in my 900sqf apartment. http://airmega.com http://airmega.com
  - infinite8s 8y ago
    Does it work well for a multiroom apartment?
- deepGem 8y ago
  You can use www.breezometer.com to check real time PM2.5 readings in your location. Based on that you can figure out whether you need an air filter or not.
- jonathankoren 8y ago
  Purpleair.com has a map of of sensors that update in near real time you can look at.
  - mturmon 8y ago
    That is a cool site. I had not known there was such an extensive sensor network out there. One thing to remember about the kind of location the parent comment wrote about: particulates are very local. Trace gases like O3 or CH4 can have very sharp spatial gradients - e.g., near highways, major streets, or dairy farms. You can observe sharp decreases from emission levels to background levels within 10s of meters. And PM2.5 mixes even more poorly than these trace gases, meaning PM2.5 shows sharper gradients. So, if you live in a built-up area and you really want to find out about PM2.5 due to your open window, or on your patio or backyard, you may need a very close-by measurement. You will still observe correlations between health outcomes and mean PM2.5 within, say, one 1km^2 monitoring footprint versus an adjacent footprint. So the background level is definitely telling you something.
b_b 8y ago
I'd recommend anyone who would like to clean the air of the home to use products from SmartAir [1] which is as inexpensive as just a fan attached to a filter, both of which they sell (although you can just buy the filter by itself and attach it to a fan you already own). I visited their office in China and received a complementary filter, which when installed in my hotel room in Beijing, definitely cleared the air and there was a noticeable difference from such a simple mechanism. Recommended for both price and effectiveness. [1] = https://smartairfilters.com/cn/en/?r=global https://smartairfilters.com/cn/en/?r=global
- clumsysmurf 8y ago
  Correct me if I'm wrong, but the fans in these units appear to be axial — but ideally you would want centrifugal fans for this application.
- sberder 8y ago
  I wouldn't, I've used their filters and followed them from the very beginning. It is an inexpensive solution but comes with its own serious flaws. They're very noisy which doesn't really work well in rooms where you actually live. They also suffer from poor CADR (Clean Air Delivery Rate) as those fans were never designed to handle high pressure differentials (before/after filter) unless you run them at full speed which is noisy. The project is interesting nonetheless, it helped demystifying purifiers and rectify the market prices in China (with other brands like Phillips and Xiaomi). Their new product for professional spaces is quite good.
- staikken 8y ago
  I've worked for a company that measures PM2.5 in the past. Using a HEPA filter to remove PM2.5 seems unlikely to me. Perhaps there's something more going on here than I've picked up from a quick skim of the site (perhaps there's some sort of cyclonic separation happening) but I'm skeptical this is actually removing particulate at that scale.
  - sberder 8y ago
    I'm not sure I get what you're saying here, HEPA is a standard that was developed for medical environments & clean rooms [1]. To qualify as HEPA, a filter should be able to remove 99.97% of particles 0.3µm and above so it is definitely impacting PM2.5 (particles 2.5µm and below). See my other comment [2] for my opinion on smartair solutions. [1] https://en.wikipedia.org/wiki/HEPA https://en.wikipedia.org/wiki/HEPA [2] https://news.ycombinator.com/item?id=17720802 https://news.ycombinator.com/item?id=17720802
darkhorn 8y ago
Enable your location in Android and then google "air pollution". It will show air poluttion in your area.
- rcMgD2BwE72F 8y ago
  Or don't tell Google your position continuously and just type "air pollution <city>"
coconut_crab 8y ago
I have always wondered what is the relationship between PM2.5 measurement and humidity/dew point. From what I have read all three types of PM2.5 sensors (beta ray, particle counting...) can't tell the difference between dust particles and water droplet. Googling around gives me a lot of conflicted answer[1][2][3]. If one looks at the air quality graph of my city[0], it can be seen that summer has much better AQI while winter/spring are worse. But I feel summer is much more dustier and spring is cleaner because the street is always wet from drizzle (dust is prevented from floating in the air). Maybe it has something to do with the lower dew point during winter/spring as my city has very high humidity, from 60% to 100% (right now it is 90%). [0] http://hanoiair.de/en_US/ http://hanoiair.de/en_US/ [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4555266/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4555266/ [2] https://www.ncbi.nlm.nih.gov/pubmed/29063278 https://www.ncbi.nlm.nih.gov/pubmed/29063278 [3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072227/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072227/
alfozan 8y ago
Air Quality Monitors Comparison: https://explorables.cmucreatelab.org/explorables/air-quality-monitor-tests https://explorables.cmucreatelab.org/explorables/air-quality...

117 points by anarbadalov 8y ago

Undark & the Pulitzer Center visited seven countries on five continents to examine the impacts of particulate pollution on the lives of everyday people, and to uncover what’s being done — or not — to address it. The project is comprised of data visualizations, short narratives, on-the-ground 360-degree videos, an explainer film, and photos from Pulitzer prizewinning photographer Larry Price. What's interesting is that PM2.5 is a measurement used by policymakers and organizations all over the world, yet the average person doesn't really know what it is, or why it matters. (I know I didn't until we began work on the project.) And it turns out that while developing nations bear the brunt of it, this kind of pollution doesn't discriminate, and it's a problem everywhere from India to Nigeria to California. In fact, a full 90% of people live in areas that exceed World Health Organization guidelines for exposure, so the odds are high that wherever you live, you’re breathing it in, too. [full disclosure: I work for Undark. We're a non-profit science and society magazine published under the auspices of the Knight Science Journalism program]

sberder 8y ago
A very interesting subject indeed, living in China and running a startup in that field, I find educating people is the biggest challenge of all!
ggm 8y ago
Do you work with the people at QUT (Brisbane) or Floreanopolis (Brazil) doing fine particulate work near airports and in hospitals? my partner did some proofreading and english-as-a-second-language with these people, fascinating stuff (as a complete outsider) and very important.
- anarbadalov 8y ago
  We don't. While we do often publish stories on public health issues, we don't conduct any of the research, we just report on the science. Australia and Brazil aren't regions we visited for this project, although I wouldn't be surprised to hear that there are areas experiencing extreme events in both.
  - ggm 8y ago
    Australia has a huge depndency on air and road freight with massive diesel subsidy to truckers and more air miles per Citizen than many other economies. We also have long hot dry weather. So the fine particulate matter issue here. Brazil has inadequate health funding and high humidity so gets mould..

gh02t 8y ago

I recently built a sensor for particulate matter (using the Plantower PMS7003, a laser-based sensor) and it's interesting to look at the effects of every day tasks. Cooking for instance causes a huge spike in PM1.0/2.5/10.0 levels, but so do more mundane tasks like vacuuming or spraying aerosols. I'd like to add a sensor for CO2, but it's a bit more complicated. A lot of the easy to use sensors marketed for the purpose are MOX sensors and the "equivalent CO2" reading they give is pretty much a complete lie except in a very narrow range of circumstances.

legulere 8y ago
I have a sensor built into an air purifier and have observed the same. Anything textile-related is bad like shaking out your blanket, which makes carpets seem horrible to me. But frying stuff really is the worst. You can go in the hundreds of micrograms, even with induction. A positive thing I have also learned is that opening the windows works best to get PM levels to a background level. Luckily it is only in the area of 5-20ug pm2.5 here For CO2 i have been recommended this one: https://clientmedia.trade-server.net/1768_tfadost/media/8/00/1800.pdf https://clientmedia.trade-server.net/1768_tfadost/media/8/00... which seems to measure CO2 directly.
- qiqing 8y ago
  Do you recommend the air purifier that you have? And would you mind sharing which one has a built-in sensor? I'd like to try measuring my laundry room.
  - sberder 8y ago
    Most purifiers on the market with built-in sensors are unreliable to measure. They usually go for cheap IR sensors without flow control. Your results will vary wildly depending on conditions (temperature and humidity affect measurements a lot). I personally like Xiaomi purifiers for their affordability and noise level. If you're concerned about measuring pm2.5 in your space, you should consider buying a good entry level monitor like the laser egg or air visual (acquired by iqair not so long ago). Don't hesitate to ask more questions, air quality had been my main business for the past 4 years.

elektor 8y ago

Does anyone have experience with buying an air quality sensor for personal use? I know of Plume and AirBeam but have not seen them in use.

rahimnathwani 8y ago
A popular one among expats where I live (Beijing) is the Laser Egg.
jonathankoren 8y ago
I have a https://www.purpleair.com/ https://www.purpleair.com/ . It measures PM 1.0, PM 2.5, and PM 10.0 . It uses the same laser scanning sensor that everyone else seems to be using, a https://learn.adafruit.com/pm25-air-quality-sensor/overview https://learn.adafruit.com/pm25-air-quality-sensor/overview , only it has two of them. You have to plug it into the wall and it communicates over wifi. Honestly, it feels a bit mom-and-pop-ish (it's literally housed in a PVC pipe.), but it seems to work. Purple Air, talks about how it uploads everything to PurpleAir.com, but their website is really really janky. Luckily, the device has a web server, and spits out data in JSON, so even if Purple Air goes belly up, your sensor should still work. I have mine integrated into http://www.weewx.com/ http://www.weewx.com/ via https://github.com/bakerkj/weewx-purpleair https://github.com/bakerkj/weewx-purpleair , and I calculate an Air Quality Index from this data using https://github.com/jonathankoren/weewx-aqi https://github.com/jonathankoren/weewx-aqi . Ideally, I'd like a sensor that calculated all the other pollutants you're supposed to track, but this is what I have. The sensor is responsive. When the smoke filtered down from the Mendocino Complex fire last week, I saw a huge spike across the particulates, and even today with the Spare The Air alert, the AQI is quite a bit elevated. The one thing I'll note about its performance, is that after installation, the sensor read abnormally high until the first rain. After that, its performance is on par with other surrounding sensors. Would I recommend it? I don't know. I feel like I should have shopped around more for one, so I can't really compare it to anything. I do like how it reports data in an open manner.
oh_sigh 8y ago
I have this one and it works quite well: https://www.amazon.com/gp/product/B071RF6B2Y https://www.amazon.com/gp/product/B071RF6B2Y I compared it with a friends much more expensive device, and the results were within 5% of each other.

clumsysmurf 8y ago

Its probably worse that it looks "Researchers from Queen Mary University of London have found that people exposed to air pollution levels well within UK guidelines have changes in the structure of the heart, similar to those seen in the early stages of heart failure." https://www.sciencedaily.com/releases/2018/08/180803103315.htm https://www.sciencedaily.com/releases/2018/08/180803103315.h...

graeme 8y ago
>In the study, average annual exposures to PM2.5 were well within UK guidelines (25µg per cubic metre), although they were approaching or past World Health Organisation (WHO) guidelines (10µg per cubic metre). What AQI do these numbers translate to?
sundvor 8y ago
That's interesting. We're looking at moving our son to a new school that's right at the corner of two major artery roads in Melbourne, with some 17 000 vehicles passing daily (just on one of them) according to VicRoads. The building doesn't appear to have a HVAC/filtration system. Playground is behind the building, but still has significant back traffic and is inside of 100-300 metres from the main roads. I'm saying that the fumes from the cars and trucks could likely have long term health impact, but struggling to convince wife of this - she says if it was that dangerous, then why wouldn't someone have done something about it? I must clearly be paranoid.. ? Personally, even though the small school appears otherwise excellent, I'm loath to expose him to these fumes. I seem to have acquired an ability to taste them whilst on my bicycle commute, and will don a Respro mask when riding the streets with the most backed up traffic.
- clumsysmurf 8y ago
  You have a legitimate concern, I've seen a few studies over the years measure VOCs as a function of distance from busy roads. Here is a very recent one: https://www.sciencedaily.com/releases/2015/04/150421105344.htm https://www.sciencedaily.com/releases/2015/04/150421105344.h... https://futurism.com/an-app-can-identify-highly-polluted-areas-in-cities/ https://futurism.com/an-app-can-identify-highly-polluted-are...

mikeyouse 8y ago

Does anyone have a sense of where the damage is done regarding PM? I live in SF and our apartment is a block away from a busy road and a gas station, both of which concern me. Not to mention the wild fires of late depositing ash all over our yard.. Also, being a SF apartment, there isn't A/C so we leave the windows open on hot days. Is there data around whether an active air filter running in a closed room before we go to sleep will help? Should it just run constantly? Is there any good method to actually lower the amount of PM I'm inhaling?

cyrildorsaz 8y ago
I bought a AirMega last year. It always runs on "quiet mode" and the PM2.5 is below 5 all the time in my 900sqf apartment. http://airmega.com http://airmega.com
- infinite8s 8y ago
  Does it work well for a multiroom apartment?
deepGem 8y ago
You can use www.breezometer.com to check real time PM2.5 readings in your location. Based on that you can figure out whether you need an air filter or not.
jonathankoren 8y ago
Purpleair.com has a map of of sensors that update in near real time you can look at.
- mturmon 8y ago
  That is a cool site. I had not known there was such an extensive sensor network out there. One thing to remember about the kind of location the parent comment wrote about: particulates are very local. Trace gases like O3 or CH4 can have very sharp spatial gradients - e.g., near highways, major streets, or dairy farms. You can observe sharp decreases from emission levels to background levels within 10s of meters. And PM2.5 mixes even more poorly than these trace gases, meaning PM2.5 shows sharper gradients. So, if you live in a built-up area and you really want to find out about PM2.5 due to your open window, or on your patio or backyard, you may need a very close-by measurement. You will still observe correlations between health outcomes and mean PM2.5 within, say, one 1km^2 monitoring footprint versus an adjacent footprint. So the background level is definitely telling you something.

b_b 8y ago

I'd recommend anyone who would like to clean the air of the home to use products from SmartAir [1] which is as inexpensive as just a fan attached to a filter, both of which they sell (although you can just buy the filter by itself and attach it to a fan you already own). I visited their office in China and received a complementary filter, which when installed in my hotel room in Beijing, definitely cleared the air and there was a noticeable difference from such a simple mechanism. Recommended for both price and effectiveness. [1] = https://smartairfilters.com/cn/en/?r=global https://smartairfilters.com/cn/en/?r=global

clumsysmurf 8y ago
Correct me if I'm wrong, but the fans in these units appear to be axial — but ideally you would want centrifugal fans for this application.
sberder 8y ago
I wouldn't, I've used their filters and followed them from the very beginning. It is an inexpensive solution but comes with its own serious flaws. They're very noisy which doesn't really work well in rooms where you actually live. They also suffer from poor CADR (Clean Air Delivery Rate) as those fans were never designed to handle high pressure differentials (before/after filter) unless you run them at full speed which is noisy. The project is interesting nonetheless, it helped demystifying purifiers and rectify the market prices in China (with other brands like Phillips and Xiaomi). Their new product for professional spaces is quite good.
staikken 8y ago
I've worked for a company that measures PM2.5 in the past. Using a HEPA filter to remove PM2.5 seems unlikely to me. Perhaps there's something more going on here than I've picked up from a quick skim of the site (perhaps there's some sort of cyclonic separation happening) but I'm skeptical this is actually removing particulate at that scale.
- sberder 8y ago
  I'm not sure I get what you're saying here, HEPA is a standard that was developed for medical environments & clean rooms [1]. To qualify as HEPA, a filter should be able to remove 99.97% of particles 0.3µm and above so it is definitely impacting PM2.5 (particles 2.5µm and below). See my other comment [2] for my opinion on smartair solutions. [1] https://en.wikipedia.org/wiki/HEPA https://en.wikipedia.org/wiki/HEPA [2] https://news.ycombinator.com/item?id=17720802 https://news.ycombinator.com/item?id=17720802

darkhorn 8y ago

Enable your location in Android and then google "air pollution". It will show air poluttion in your area.

rcMgD2BwE72F 8y ago
Or don't tell Google your position continuously and just type "air pollution <city>"

coconut_crab 8y ago

I have always wondered what is the relationship between PM2.5 measurement and humidity/dew point. From what I have read all three types of PM2.5 sensors (beta ray, particle counting...) can't tell the difference between dust particles and water droplet. Googling around gives me a lot of conflicted answer[1][2][3]. If one looks at the air quality graph of my city[0], it can be seen that summer has much better AQI while winter/spring are worse. But I feel summer is much more dustier and spring is cleaner because the street is always wet from drizzle (dust is prevented from floating in the air). Maybe it has something to do with the lower dew point during winter/spring as my city has very high humidity, from 60% to 100% (right now it is 90%). [0] http://hanoiair.de/en_US/ http://hanoiair.de/en_US/ [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4555266/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4555266/ [2] https://www.ncbi.nlm.nih.gov/pubmed/29063278 https://www.ncbi.nlm.nih.gov/pubmed/29063278 [3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072227/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4072227/

alfozan 8y ago

Air Quality Monitors Comparison: https://explorables.cmucreatelab.org/explorables/air-quality-monitor-tests https://explorables.cmucreatelab.org/explorables/air-quality...