Sensor.Community — Stuttgart's €30 DIY Kit That Grew Into the World's Largest Citizen Air-Quality Network

Sensor.Community (originally luftdaten.info) began in 2014–2015 when Jan Lutz and fellow volunteers at Open Knowledge Lab Stuttgart could not obtain fine-grained particulate-matter data from the city and decided to measure it themselves. After a year of prototyping — including an adapted air-conditioner part — the group settled on the low-cost SDS011 particulate sensor, packaged into an open-hardware kit costing roughly €30 that anyone can solder and mount on a windowsill.
The design spread by direct replication rather than institutional rollout: early reports counted around 5,000 self-built kits, concentrated in Germany, the Netherlands and Bulgaria; by the mid-2020s, third-party aggregator AQICN was tracking over 35,000 live Sensor.Community stations worldwide, making it the largest citizen-run air-quality network of its kind. All readings are published as open data on a live map refreshed every 2.5 minutes.
Independent laboratory evaluation of the SDS011 sensor at the network's core (Budde et al.) found it performs well for fine PM2.5 particles but is markedly less reliable for coarser PM10, with inter-unit error rates reported as high as 10–37% for PM10 versus 9–24% for PM2.5 — a caveat that limits the network's use for regulatory-grade compliance monitoring even as it remains a valuable indicator of relative local air-quality patterns and a training ground for civic-tech chapters worldwide.

Read the full analysis: https://sensor.community/en/