Low-cost sensors have helped communities see the air quality, but experts are still debating whether data are accurate or not. In many cases, monitor manufacturers have to turn to data manipulation in order to get accurate results, but it is time to step up by deploying better sensor technology.
The technology exists and we should take advantage of it as soon as possible. Almost always, the first thing I am asked about sensors is how accurate they are. Well, this question has a very tricky answer. In many cases, we measure accuracy by comparing a low-cost sensor with a reference monitor, which worths thousands of dollars. However, the comparison is not always fair. For example, if the XYZ company sends their monitor for evaluation during a high humidity season then unless they have a heater or dryer at the inlet to remove humid droplets of water from the samples before measurement then the results from the correlation would be catastrophic.
Unfortunately, low-cost sensors lack repeatability, which means that if you feed the sensors with the same sample of air (by splitting an inlet into two inlets) they won’t be able to give the same particle count. Not only that, low-cost sensors are not very good at differentiating the size of the particles and they end up estimating values. The most common example is that they give an estimation for PM1.0 and PM10, which is an arithmetical calculation that comes from the value of the PM2.5 bin by subtracting 2 μg/m3 and adding 2μg/m3, respectively.
As you can understand some companies falsely claim that their sensor/monitor can measure PM1.0 and PM10. People get confused all the time by the data they obtain and in most cases, they try to reach me in order to clear their confusion.
I really support Citizen Science Air Quality Projects, but I feel that the people behind these projects struggle with the data they obtain because they are not accurate enough for them to use in a court. There is a real movement, but they need better tools to fight the injustice. It is well-know that clean air is a right. Unfortunately, we don’t breathe clean air because the rulers of this world still don’t get it. The same way nothing is done about climate change.
The heart of an Air Quality Monitor is the sensor (the electronic component). Now, if the sensor is also the brain of the monitor, then you have a very powerful instrument in your hands that can help you discover the air you breathe with accuracy and repeatability. Keep in mind something very important. For a sensor to be accurate, real calibration methods need to be deployed and standards need to be adopted.
I think, we are transitioning towards more reliable and sustainable solutions rather than cheap ones.
If you wish to learn more about the technology and how accuracy can be achieved, drop me a message.
3 thoughts on “Low-Cost Sensors, Do They Hold Up To The Hype?”
DIY Citizen Science is a vital thing. Perhaps explore the other side – the network of activism that is created. While it is true that a $25 sensor may not be hugely accurate, the data holds some value. The question remains – who will look at it? Should be organized around eventual data consumption.
Also – to increase the types of data (ozone, NO) sensors even if they are not hugely accurate.
And ultimately DIY CS should become more robust and venerable and easier to deploy.
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Thank you very much about your newsletter.
I had two questions regarding this remark that you made :
“The most common example is that they give an estimation for PM1.0 and PM10, which is an arithmetical calculation that comes from the value of the PM2.5 bin by subtracting 2 μg/m3 and adding 2μg/m3, respectively.”
– Do you have a scientific reference related to this issue ? Or a link to a webpage talking about this issue?
– Do you think that PMS7003 also has this issue ?
Some of us at York University in Toronto are also working with air quality sensors – we’re looking at how accurate they are from a scientific standpoint as well as why and how people use them. Would you be interested in being interviewed as part of our research? Please drop us a line at ***@***.ca. You can learn more about our research at https://air.glendon.yorku.ca.
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