> I wrote this article a few weeks ago after discovering that a well known air quality monitor in the market that retails for more than USD 1000 actually uses a

> I wrote this article a few weeks ago after discovering that a well known air quality monitor in the market that retails for more than USD 1000 actually uses a PM module that costs less than USD 20. This may be true for off the shelf air sensors, but in general the base cost of the sensor is not necessarily correlated with achievable accuracy. There are even manufacturers like Maxim who will sell you sensors for cheap, but you pay a lot to license firmware to get the best performance (and in this case actually a smoke/particle detector if I remember right - the MAX30105). You might pay thousands for a third party calibration on top of the OEM device. For example an infrared calibration target is a puck of coarsely machined metal, a heater cartridge and some black paint, but you're paying $$$ for NIST traceability, guaranteed measurements of the emissivity, etc. https://hackaday.com/2017/04/11/ask-hackaday-how-does-this-air-particle-sensor-work/ https://hackaday.com/2017/04/11/ask-hackaday-how-does-this-a... https://www.sciencedirect.com/science/article/pii/S0021850221005644 https://www.sciencedirect.com/science/article/pii/S002185022...