It is worth adding http://purpleair.com/ http://purpleair.com/ who produce the low cost sensors that contribute to at least the first map. They have their own m

It is worth adding http://purpleair.com/ http://purpleair.com/ who produce the low cost sensors that contribute to at least the first map. They have their own map (with 80 second update intervals) and you can buy a sensor for ~$250... it is a cool product because its a super practical design (housing is a pvc pipe cap) focused on delivering an accurate sensor on the cheap. We love ours because you can watch it and see in real time when the air quality improves for a brief period.