Started in 2018, the open-seneca initiative has deployed pilot citizen science networks of low-cost air quality sensors in cities in the UK (Cambridge), Argentina (Buenos Aires and Mendoza), Kenya (Nairobi), and Brazil (Belo Horizonte). The team has in-depth experience in the design of open-source, mobile, low-cost air quality monitors and capacity building in partner cities, the education and engagement of citizens, and calibration, analysis, and visualisation of the data collected with the low-cost sensors to aid with decision making.