1. A method of identifying an airborne molecular contamination (AMC) leaking source in a fab, the method comprising: determining a minimum number of AMC sensors needed to collect AMC measurement data for all areas of the fab; distributing the minimum number of AMC sensors in the fab; connecting the AMC sensors to an AMC monitor having an alarm; using a computer, building a database of spatial response probability distribution matrices of the AMC sensors using a unit AMC value at locations of the AMC sensors; and upon a condition that the alarm is triggered by the AMC sensors, collecting AMC measurement data from the AMC sensors, and identifying an AMC leaking source using the AMC measurement data and the database without running a real-time inverse CFD simulation during the collection of AMC measurement data.