There's no sensor within 200km of me on purpleair.com, but it still shows a value (a scary one).
Looking at the purpleair map, it seems to be choosing the closest one? Which for me is really far / in another country.
Looking at the purpleair map, it seems to be choosing the closest one? Which for me is really far / in another country.
Maybe it helps: there's also http://waqi.info/ which has a decent API, but more importantly a lot more coverage (at least in Europe).