5 ms·

This looks really cool! Could you confirm one thing though, which I can't find on your site after ~5 minutes of searching? Do your PM2.5 sensors truly measure

This looks really cool! Could you confirm one thing though, which I can't find on your site after ~5 minutes of searching? Do your PM2.5 sensors truly measure PM2.5 or is it doing an approximation based on factors (many sensors supposedly do this). If it's the former, it might be useful to make that more clear on your site as I could not confirm it.

jauer 3y ago
Their website mentions the sensor they use directly on the kits page. It's a Plantower PMS5003 which does actually count particles: https://www.aqmd.gov/docs/default-source/aq-spec/resources-page/plantower-pms5003-manual_v2-3.pdf https://www.aqmd.gov/docs/default-source/aq-spec/resources-p...
- dhhagan 3y ago
  While the spec sheet does say that, it's not actually true. The PMS5003 is a truncated nephelometer (https://amt.copernicus.org/articles/15/655/2022/ https://amt.copernicus.org/articles/15/655/2022/) that measures the total scattered light from all particles with diameters less than ~1 µm. This single scalar value (proportional to the total scattered light, as collected across a wide viewing range) is then correlated to a reference measurement of PM2.5 and typically correlates quite well in most urban areas where PM2.5 and PM1 are highly correlated. For more info on the difference between particle counters and nephelometers in this context, see https://amt.copernicus.org/articles/13/6343/2020/ https://amt.copernicus.org/articles/13/6343/2020/.
  - jauer 3y ago
    TIL! Thank you for the detailed explanation and links to additional context.
ahaucnx 3y ago
We use the Plantower PMS5003 sensor for PM2.5. This sensor has been extensively tested and is one of the most accurate low cost sensors. All low cost sensors are using the laser scattering technique and thus do approximate the mass and not a direct measurement. However tests show that PM2.5 is the most accurate and often PM10 in these sensors is not very good.
- throwoutway 3y ago
  Thanks for the response!
honk 3y ago
Relevant disclaimer: I work for QuantAQ, another distributed Air Quality Monitoring company, my opinions are my own. With proper calibration, the PMS5003 sensor AirGradient uses is a real and fairly good measurement of PM1 (<1 micron), which is often fairly correlated with (and makes up much of) PM2.5. However, the sensor cannot really see particles larger than 1 micron, which sometimes matters for PM2.5 (when the PM1:PM2.5 ratio changes, like wildfires), and very much matters for PM10. That's why QuantAQ uses a PMS5003 combined with a different sensing technology (an optical particle counter) to actually measure PM2.5 and PM10, not just extrapolate from a PM1 measurement. We have a blog post here explaining more: https://blog.quant-aq.com/can-your-plantower-pms5003-based-air-quality-sensor-measure-pm10/ https://blog.quant-aq.com/can-your-plantower-pms5003-based-a... I love the work that AirGradient is doing making AQ sensing technology open and accessible, especially to hardware hackers. The BOM cost of the OPC sensor we use alongside the PMS5003 is more than the cost of the entire AirGradient kit, so it is valuable to have options in the market depending on application.
- ahaucnx 3y ago
  Thank you for sharing this. Are you using the AlphaSense OPC?
  - aidenn0 3y ago
    I'm just going to take a minute to be happy to see this friendly exchange of information in public between two people who are both knowledgeable about the subject and competitors.
- geerlingguy 3y ago
  Excellent overview; I think the space for air monitoring is only going to grow as time goes on, especially after COVID and with increased awareness of the downsides of airborne particulates and high CO2 exposure.
  - alias_neo 3y ago
    I've been setting up PM sensors in my home since installing a log-burning stove last winter; I've found a couple of interesting things thus far; Notably, despite the FUD, air quality _in_ my home isn't affected by it. What does affect air quality in my home massively, are the people parking their vehicles surrounding my home morning and afternoon as they drop off and pick up their children from the nearby school. I see a 10x ambient measure at these times. I was starting to think about how I could use BLE monitoring to track this somehow (the other thing my home is surrounded with at these times is devices broadcasting Bluetooth "beacons"(?)); could be an interesting experiment. The next step for me is really knowing what and how something can be done about the pollution (generally speaking); Monitoring is great, but what's the next step?

jauer 3y ago

Their website mentions the sensor they use directly on the kits page. It's a Plantower PMS5003 which does actually count particles: https://www.aqmd.gov/docs/default-source/aq-spec/resources-page/plantower-pms5003-manual_v2-3.pdf https://www.aqmd.gov/docs/default-source/aq-spec/resources-p...

dhhagan 3y ago
While the spec sheet does say that, it's not actually true. The PMS5003 is a truncated nephelometer (https://amt.copernicus.org/articles/15/655/2022/ https://amt.copernicus.org/articles/15/655/2022/) that measures the total scattered light from all particles with diameters less than ~1 µm. This single scalar value (proportional to the total scattered light, as collected across a wide viewing range) is then correlated to a reference measurement of PM2.5 and typically correlates quite well in most urban areas where PM2.5 and PM1 are highly correlated. For more info on the difference between particle counters and nephelometers in this context, see https://amt.copernicus.org/articles/13/6343/2020/ https://amt.copernicus.org/articles/13/6343/2020/.
- jauer 3y ago
  TIL! Thank you for the detailed explanation and links to additional context.

ahaucnx 3y ago

We use the Plantower PMS5003 sensor for PM2.5. This sensor has been extensively tested and is one of the most accurate low cost sensors. All low cost sensors are using the laser scattering technique and thus do approximate the mass and not a direct measurement. However tests show that PM2.5 is the most accurate and often PM10 in these sensors is not very good.

throwoutway 3y ago
Thanks for the response!

honk 3y ago

Relevant disclaimer: I work for QuantAQ, another distributed Air Quality Monitoring company, my opinions are my own. With proper calibration, the PMS5003 sensor AirGradient uses is a real and fairly good measurement of PM1 (<1 micron), which is often fairly correlated with (and makes up much of) PM2.5. However, the sensor cannot really see particles larger than 1 micron, which sometimes matters for PM2.5 (when the PM1:PM2.5 ratio changes, like wildfires), and very much matters for PM10. That's why QuantAQ uses a PMS5003 combined with a different sensing technology (an optical particle counter) to actually measure PM2.5 and PM10, not just extrapolate from a PM1 measurement. We have a blog post here explaining more: https://blog.quant-aq.com/can-your-plantower-pms5003-based-air-quality-sensor-measure-pm10/ https://blog.quant-aq.com/can-your-plantower-pms5003-based-a... I love the work that AirGradient is doing making AQ sensing technology open and accessible, especially to hardware hackers. The BOM cost of the OPC sensor we use alongside the PMS5003 is more than the cost of the entire AirGradient kit, so it is valuable to have options in the market depending on application.

ahaucnx 3y ago
Thank you for sharing this. Are you using the AlphaSense OPC?
- aidenn0 3y ago
  I'm just going to take a minute to be happy to see this friendly exchange of information in public between two people who are both knowledgeable about the subject and competitors.
geerlingguy 3y ago
Excellent overview; I think the space for air monitoring is only going to grow as time goes on, especially after COVID and with increased awareness of the downsides of airborne particulates and high CO2 exposure.
- alias_neo 3y ago
  I've been setting up PM sensors in my home since installing a log-burning stove last winter; I've found a couple of interesting things thus far; Notably, despite the FUD, air quality _in_ my home isn't affected by it. What does affect air quality in my home massively, are the people parking their vehicles surrounding my home morning and afternoon as they drop off and pick up their children from the nearby school. I see a 10x ambient measure at these times. I was starting to think about how I could use BLE monitoring to track this somehow (the other thing my home is surrounded with at these times is devices broadcasting Bluetooth "beacons"(?)); could be an interesting experiment. The next step for me is really knowing what and how something can be done about the pollution (generally speaking); Monitoring is great, but what's the next step?