Smart Emission 2 focuses on citizen science for air quality and low-cost participatory monitoring of environmental qualities in cities. This follow-up project focuses on Data Visualization, Data Use by citizen scientists, Data Quality, and Communication. The project has four objectives: 1. Developing a multi-sensor-approach for low-cost citizen sensing, and improve a shared Sensor Spatial Data Infrastructure (sensor SDI) by connecting and re-using data portals, API’s, and sensor types. 2. Development and participatory assessment of a toolkit for flexible Sensor Data Visualization 3. Experiment with the data quality of the sensor data, assessing fitness-for-purpose 4. Communicating with a Linked-Data Concept Map, citizens can learn and educate others on the key concepts and metadata provided with sensor tools, data-infrastructure and data quality assessment. Representatives of citizen initiatives are included in this study, following principles of citizen science.