It frustrates me that there are so many of these networks and they don't talk to each other. I deliberately went with a system that measures multiple values, but then I see other people going "we only measure one thing instead of nine so our units cost half as much".
I should try to script at least my systems so they write into as many of the open networks as I can manage.
Unfortunately, yes, the space is fragmented. A long while ago I chose https://luftdaten.info/en/ because sensor firmware, DB, and tools are truly open source (GPL, ODbL, MIT). Next to supporting many sensors, it also allows for your own back-ends (API, InfluxDB). The community is awesome and has hacker values.
The inexpensive part makes citizen science viable in sub-economic and hobbyist settings.
https://openaq.org/ is trying to consolidate air quality data, but I'm uncertain of their licensing and goals.
Sorry for a pointless post, but this project gives me the CCC vibes. Y'all should attend one day, it's brilliant! In fact it's so rich in things and hacker exhibitions that you don't even have to go to the talks!
The 36th Chaos Communication Congress organized by the Chaos Computer Club, a traditional event run by the community for the community. Takes place from Dec 26 to Dec 30 in Leipzig (Germany). Tickets are available on this Thursday (November 21th) from 21:00:00 CET till, judging from past experience, 21:00:01 CET.
For clarification: CCC is used for Chaos Computer Club, who organizes the C3, the Chaos Communication Congress. Confusion guaranteed ;) for more info visit https://events.ccc.de/
Build your own inexpensive sensor, contribute to the global network. See also https://github.com/opendata-stuttgart