Name: Watch air (pollution)
Author: Fietser

Widget displaying Air Quality Index and data (in μg/m3) about polluting gases, such as Carbon monoxide (CO), Nitrogen monoxide (NO), Nitrogen dioxide (NO2), Ozone (O3), Sulphur dioxide (SO2), Ammonia (NH3), and particulates (PM2.5 and PM10). 

Setup

Get Open weather API key.

See `https://openweathermap.org/api` for registering and creating an API key.
Put this key in setting `Open weather map API key`, using the Garmin Express.

More settings are on the watch.
NB. When showing `ppm` instead of `μg/m3`, the PM10 and PM2.5 values remain in `μg/m3`.