With growing transportation and population density, increasing global warming and sudden climate change, air quality is one of the critical measures that is needed to be monitored closely on a real-time basis in today’s urban ecosystems. This paper examines the issues, infrastructure, information processing, and challenges of designing and implementing an integrated sensing system for real-time indoor air quality monitoring. The system aims to detect the level of seven gases, ozone (O ₃ ), particulate matter, carbon monoxide (CO), nitrogen oxides (NO ₂ ), sulfur dioxide (SO ₂ ), volatile organic compound, and carbon dioxide (CO ₂ ), on a real-time basis and provides overall air quality alert timely. Experiments are conducted to validate and support the development of the system for real-time monitoring and alerting.