Bettair is a Platform as a Service (PaaS) that permits, for the first time, to really map air pollution in cities on a previously unimaginable scale based on a large deployment of outstandingly accurate gas sensors by using an advanced post-processing algorithm. This information allows applying appropriate urban plans for enhancing air quality and to make smart and better decisions to mitigate air pollution. Bettair is a network of autonomous devices that are installed in streetlights (or in city furniture) in a dense matrix distanced between 0.5÷1 km allowing a high spatial and temporal resolution. The nodes are incorporating: 6 electrochemical sensors to measure gases, an Optical Particle Counter to measure PMs, noise pollution, and other ambient quality indicators. A complete front and back-end solution is provided to municipalities and an APP for the citizens. The technology has been tested in 8 European countries and in New York City.