Mobile and Low-Cost Measurement Systems for Indoor and Outdoor Urban Air Quality Characterization

In a rapidly changing world characterized by increasing urbanization and climate change, urban air quality monitoring is essential for advancing fundamental process understanding, assessing environmental impacts, understanding human exposure to air pollution, and supporting evidence-based mitigation strategies in densely populated areas.
The TROPOS Institute has a long-standing track record in developing and applying mobile measurement systems for the comprehensive characterization of aerosol particle properties, including particulate matter (PM), particle number size distributions, and black carbon (BC), which are key indicators of urban air quality. The institute’s expertise spans from hardware design and sensor integration to laboratory-based calibration and long-term quality assurance. Building on these mobile “backpack” platforms and leveraging state-of-the-art low-cost sensor technology, further miniaturized sensor packages have been developed for different indoor and outdoor applications in scientific, as well as engagement and educational projects.
These activities represent a continuous and iterative development process, with systems being regularly adapted to emerging scientific needs and technological advances. A major emphasis is placed on the development of scalable data infrastructures aligned with Internet-of-Things (IoT) concepts. This includes the implementation of MQTT-based communication protocols and the integration of SQL-based database solutions for reliable data storage, management, and analysis. As a result, these developments enable real-time data analysis and facilitate deployment in sensor networks as key improvements. 
The developed instruments are applied across a wide range of interdisciplinary scientific contexts, including local and regional atmospheric studies, large-scale European research projects, but also education and knowledge transfer activities. They support high-resolution, spatiotemporal observations of particulate air quality in diverse urban and indoor environments, providing robust tools for both scientific research and practical applications. As an example, modular low-cost instruments combined with an innovative interactive online platform were successfully applied in the collaborative educational project EngageMINT, in which more than 150 young participants measured air quality parameters and were engaged for environmental topics together with scientists. Furthermore, 15 innovative and very user-friendly devices, named AQBIE (Air Quality Beacon and Immission Evaluator), were developed and applied for several months in a different study exploring indoor air quality to capture seasonal effects of air pollution, mainly the impact of winter biomass burning.