In fact, as a result of different traffic and urban ventilation conditions, the air quality can vary widely from one street to another in dense urban cities like Hong Kong. The PRAISE-HK app maps air quality variation down to individual streets, allowing users to proactively plan their time and activities and reducing exposure from high pollution. While air pollution is still a major environmental and health concern in Hong Kong, Prof. Alexis Lau of HKUST Division of Environment and Sustainability, and PRAISE-HK Principal Investigator, said “Many people believed that there is not much that can do to reduce their exposure to air pollutants.