Citizen Science: low cost approaches to measuring Air Pollution
I should say at the outset that there is (or rather soon will be) a lot more material and information on all of these topics and discussions in the Bibliography, most of which is stored off site in a Google Docs cloud store. I will regularly add to this as I come across things.
Measuring average NO2 and NOx is relatively easy (provided you follow the instructions!) and cheap using the diffusion tubes mentioned previously from the likes of Gradko. Work is still in progress to find an affordable instantaneous measurement of these gasses given the limited sensitivity of available cheap electronic sensors, but I would expect this to improve in the relatively near future as several groups are currently working on this.
As we have seen in the "professional" section, one way of detecting and measuring particulates is by the light scattered by a laser beam from air passing through a small darkened chamber with the scattering detected by a photocell and analysed by software to give particle density for different particle sizes e.g. PM10, PM2.5, PM1.
The first really cheap sensor of this kind to be readily available was the Shinyei PPD42, see this and this - more in the bibliography.
This sensor is inherently quite crude, but nonetheless useful and was originally designed for monitoring the effectiveness of air purifiers for example in clean rooms and operating theatres. But the usefulness and low cost (£15ish) of the sensor did not go unnoticed by companies and groups wanting to measure air quality at an affordable cost. Examples of citizen science devices using the PPD42 are from instructibles here, the Dustduino, see here, and the more developed Airbeam, here.
All of these suffer from the limited accuracy of the PPD42 which relies on a heater and consequent hot air rising to provide air flow, which is inherently approximate to start with, but also means that the sensor must be kept upright if it is to work properly.
But ... they do the job, and begin to be comparable to the "professional" equivalents at a fraction of the cost. Several companies in China then saw an opportunity, and developed similar but more accurate sensors, principally using a speed controlled fan to draw an accurate airflow through the device. Spinoffs from this are the Laser Egg, http://kaiterra.com/uk/store/, and a lot more devices in China most of which are not currently available here - see https://www.thebeijinger.com/blog/2016/01/02/which-iaq-monitor-should-i-buy
The only affordable monitors from the US are the Dylos range which have a good reputation but do not display readings in the right format for the UK and EU air pollution limits although third party software is available to sort this. See here. The more expensive Dylos monitors allow you to download readings to a computer for data logging. Honeywell in the US make sensors, see here.
I should say at some point that, whether professional or citizen science, ALL sensors based on drawing air through a chamber where laser light is scattered have typically a 3 year reliable life, after which dust and dirt accumulating in the chamber mean the device will become inaccurate and eventually cease to function. So ideally the device design should be such that sensors should be capable of being replaced.
I now come to the current state of citizen science measurement.
The early citizen science devices described above used the Arduino platform for the computing element, with software written in the Arduino Sketches programming language. Subsequent developers have taken advantage of more accurate sensors, principally the SDS011 from Chinese firm Nova Fitness which is a spin-off from Shandong University - see http://www.inovafitness.com/en/a/index.html. These are available from Aliexpress in China for about £15 each, see http://bit.ly/2G9gPmu,
and almost all developers have continued to use Arduino family computing boards and Sketches software.
There are several different citizen science developed monitors in the Bibliography, but I am going to highlight the two that I think are of most immediate use which are the sensors on the Luftdaten website http://luftdaten.info/en/home-en/ which have been developed by OK Labs in Stuttgart (Open Knowledge Labs which has worldwide branches), https://codefor.de/stuttgart/ and also known as @airrohr sensors on Twitter. See also https://codefor.de/en/stadtgeschichten/1feinstaub/ and www.youtube.com/watch?v=ift71TOu91w&feature=youtu.be
Instructions for making this standard sensor are also here https://www.byteyourlife.com/en/household-tools/particulate-matter-sensor-controller-project-luftdaten-info/7204 , and the network of this type of sensor in the UK is increasing rapidly, with the Bristol network of Air Apparent currently leading - see https://airapparentuk.wordpress.com/what-we-do/.
A potentially significant problem with Citizen Science projects and measurements, certainly in England, is that they are not taken seriously by "officialdom", and assumed to be inaccurate. I suspect this often because it is convenient to do so!
An example is the air pollution modelling dome by Plumeplotter, see http://plumeplotter.com/, which was rubbished by Plymouth Council, see https://www.liverpoolecho.co.uk/news/public-urged-not-rely-on-11886181. Plumeplotter, which I have mentioned elsewhere, makes the valid point that they are using data from the incinerator planning application, putting the data into the official American software tool (AERMOD) and displaying it. But they get rubbished. In some contrast, in the USA, the EPA, the Environmental Protection Agency, who are also the custodians of AERMOD and where its use is mandatory, have also done some very useful evaluation of low cost particulate sensors - see https://www.epa.gov/air-sensor-toolbox and https://www.epa.gov/air-sensor-toolbox/evaluation-emerging-air-pollution-sensor-performance. Similarly SEPA in Scotland, the Scottish Environmental Protection Agency, takes citizen science seriously - see https://www.environment.gov.scot/our-environment/air/air-quality-and-citizen-science/
The EU has fully funded a project on citizen science air pollution measurement called HackAIR, http://www.hackair.eu/, under the Horizon 2020 funding stream with highly reputable partners. HackAIR has designed its own sensor system, but will be working with Luftdaten.
I should say at the outset that there is (or rather soon will be) a lot more material and information on all of these topics and discussions in the Bibliography, most of which is stored off site in a Google Docs cloud store. I will regularly add to this as I come across things.
Measuring average NO2 and NOx is relatively easy (provided you follow the instructions!) and cheap using the diffusion tubes mentioned previously from the likes of Gradko. Work is still in progress to find an affordable instantaneous measurement of these gasses given the limited sensitivity of available cheap electronic sensors, but I would expect this to improve in the relatively near future as several groups are currently working on this.
As we have seen in the "professional" section, one way of detecting and measuring particulates is by the light scattered by a laser beam from air passing through a small darkened chamber with the scattering detected by a photocell and analysed by software to give particle density for different particle sizes e.g. PM10, PM2.5, PM1.
The first really cheap sensor of this kind to be readily available was the Shinyei PPD42, see this and this - more in the bibliography.
This sensor is inherently quite crude, but nonetheless useful and was originally designed for monitoring the effectiveness of air purifiers for example in clean rooms and operating theatres. But the usefulness and low cost (£15ish) of the sensor did not go unnoticed by companies and groups wanting to measure air quality at an affordable cost. Examples of citizen science devices using the PPD42 are from instructibles here, the Dustduino, see here, and the more developed Airbeam, here.
All of these suffer from the limited accuracy of the PPD42 which relies on a heater and consequent hot air rising to provide air flow, which is inherently approximate to start with, but also means that the sensor must be kept upright if it is to work properly.
But ... they do the job, and begin to be comparable to the "professional" equivalents at a fraction of the cost. Several companies in China then saw an opportunity, and developed similar but more accurate sensors, principally using a speed controlled fan to draw an accurate airflow through the device. Spinoffs from this are the Laser Egg, http://kaiterra.com/uk/store/, and a lot more devices in China most of which are not currently available here - see https://www.thebeijinger.com/blog/2016/01/02/which-iaq-monitor-should-i-buy
The only affordable monitors from the US are the Dylos range which have a good reputation but do not display readings in the right format for the UK and EU air pollution limits although third party software is available to sort this. See here. The more expensive Dylos monitors allow you to download readings to a computer for data logging. Honeywell in the US make sensors, see here.
I should say at some point that, whether professional or citizen science, ALL sensors based on drawing air through a chamber where laser light is scattered have typically a 3 year reliable life, after which dust and dirt accumulating in the chamber mean the device will become inaccurate and eventually cease to function. So ideally the device design should be such that sensors should be capable of being replaced.
I now come to the current state of citizen science measurement.
The early citizen science devices described above used the Arduino platform for the computing element, with software written in the Arduino Sketches programming language. Subsequent developers have taken advantage of more accurate sensors, principally the SDS011 from Chinese firm Nova Fitness which is a spin-off from Shandong University - see http://www.inovafitness.com/en/a/index.html. These are available from Aliexpress in China for about £15 each, see http://bit.ly/2G9gPmu,
and almost all developers have continued to use Arduino family computing boards and Sketches software.
There are several different citizen science developed monitors in the Bibliography, but I am going to highlight the two that I think are of most immediate use which are the sensors on the Luftdaten website http://luftdaten.info/en/home-en/ which have been developed by OK Labs in Stuttgart (Open Knowledge Labs which has worldwide branches), https://codefor.de/stuttgart/ and also known as @airrohr sensors on Twitter. See also https://codefor.de/en/stadtgeschichten/1feinstaub/ and www.youtube.com/watch?v=ift71TOu91w&feature=youtu.be
Instructions for making this standard sensor are also here https://www.byteyourlife.com/en/household-tools/particulate-matter-sensor-controller-project-luftdaten-info/7204 , and the network of this type of sensor in the UK is increasing rapidly, with the Bristol network of Air Apparent currently leading - see https://airapparentuk.wordpress.com/what-we-do/.
A potentially significant problem with Citizen Science projects and measurements, certainly in England, is that they are not taken seriously by "officialdom", and assumed to be inaccurate. I suspect this often because it is convenient to do so!
An example is the air pollution modelling dome by Plumeplotter, see http://plumeplotter.com/, which was rubbished by Plymouth Council, see https://www.liverpoolecho.co.uk/news/public-urged-not-rely-on-11886181. Plumeplotter, which I have mentioned elsewhere, makes the valid point that they are using data from the incinerator planning application, putting the data into the official American software tool (AERMOD) and displaying it. But they get rubbished. In some contrast, in the USA, the EPA, the Environmental Protection Agency, who are also the custodians of AERMOD and where its use is mandatory, have also done some very useful evaluation of low cost particulate sensors - see https://www.epa.gov/air-sensor-toolbox and https://www.epa.gov/air-sensor-toolbox/evaluation-emerging-air-pollution-sensor-performance. Similarly SEPA in Scotland, the Scottish Environmental Protection Agency, takes citizen science seriously - see https://www.environment.gov.scot/our-environment/air/air-quality-and-citizen-science/
The EU has fully funded a project on citizen science air pollution measurement called HackAIR, http://www.hackair.eu/, under the Horizon 2020 funding stream with highly reputable partners. HackAIR has designed its own sensor system, but will be working with Luftdaten.