Air pollution monitoring and impact assessment represents a major objective especially for large and industrial cities, driven by the need to improve citizen liveability. In order to address this challenge and avoid increasing monitoring costs, attention is now being redirected towards using low-cost sensing units and an opportunistic citizen sensing. This paper proposes a comparative study of using various air quality monitoring devices such as: high-reliable fixed air pollution stations, fixed smaller passive tubes and smart mobile sensors, tested through field measurements and citizen sensing in an eco-neighbourhood from Lorraine, France. The air quality evaluation is done through two experimenting protocols. The first protocol involves the installation of passive tubes for monitoring the NO2 concentration levels inside the eco-neighbourhood, placed in strategic locations highly affected by traffic circulation. The second experimentation protocol aimed at monitoring the NO2 levels registered at the human level by citizens travelling daily inside the neighbourhood and carrying with them the smart pollution sensor. The findings revealed that the mobile sensors carried at the human level (approximatively at 1.5 meters altitude) detected higher NO2 concentrations which would sometimes be between three to five times higher than the passive-static monitoring tubes (placed at 3 meters altitude).