In 2003, Hong Kong was hit by Severe Acute Respiratory Syndrome (SARS) from which many peopledied. The Hong Kong Government subsequently set up a Governmental Team Clean Committee toinvestigate possible urban design policies. Team Clean charged the task to the Planning Department,HKSAR. It initiated a study titled: Feasibility Study for Establishment of Air Ventilation Assessment(AVA) System. In 2003, the research contract was entrusted to a team of researchers of Departmentof Architecture, CUHK. A number of focused studies were conducted.