I reviewed some potential data sources for populating PM2.5 data in our service launch. Short Answer:
LASS.
tldr;
What I have discovered is that all roads that I am aware of lead back to 2 or 3 data sources:
LASS - (visualization:
http://airmap.g0v.asper.tw/) - Location Aware Sensor System. Crowdsourced data. Their data comes from citizens using LASS homemade devices and
Airbox devices (made by Edimax). The network has about 1100 nodes in Taiwan and about 300 sites in Taipei. Check out their visualization and play with some of the parameters. They have open and free endpoints. Source code for devices and services under MIT License on github.
Taiwan EPA - The Taiwan government has their own monitoring stations including mobile ones throughout Taiwan. I am guessint about 100 monitoring sites in Taiwan, and 5 - 10 in Taipei City. Other companies, including LASS, use their data.
(which may be using Taiwan's EPA Data) - A private network for air quality monitoring. They have about 7,000 monitoring locations worldwide and use airflow and other models to predict other points. Unknown if they have their own monitoring stations in Taiwan or how many they have.