...and here I am, nice to "meet" you!
I've read the interesting document you posted from EPA, and I can give some feedbacks regarding what JRC did on this argument (the European experience!).
They tested several "low cost" sensors (low cost if compared to the so called fiduciary ones).
They worked within the FP7 MACPoll Project with many institutes of metrology to face with these devices in the best way possible. They understood some "rules" and the most important (in my opinion) are:
1. it is definitely difficult to individuate the "best" sensor for a specific parameter amongst the panorama they investigated (due to different factors such as cross sensitivity to other substances, reliability, etc.).
2. what is better to do is to combine some of them (even based on different technologies) to improve the possibility to manage data. For example, in regard with Ozone, it is possible to combine an electrochemical sensor with a MICS one (metal oxide semiconductors gas sensors) for NO2 to face with cross sensitivity.
We also worked on some configurations regarding air quality and compliant with the ACRONET Paradigm. Our experience led us to understand that:
a. if low cost measuring instruments are adopted, every installation requires a specific calibration. Then, the right process impose to test the instruments as much possible close to a fiduciary station (if available) measuring the same parameter of your interest. After this period, the analysis of the data sets will allow to extract the best fitting curve of calibration (for that site!!).
b. it is possible to develop a really low cost station for air quality monitoring but, in some cases, it is necessary to simplify the constraints. Furthermore, there are some sensors available on the market that, even if really low costs, are completely useless to monitor the interesting variables (i.e. the Particulate Matter). The evaluation phase (where both costs and project requirements must be put in relation) that lead to the selection of the measuring instruments becomes crucial.
Forgive me for the poem, please!
Best regards,
Adriano