Abstract: A method and system for use in monitoring/evaluating industrial process such as, for example, plasma processes useful in the fabrication of semiconductor chips, microelectromechanical devices, and the like on semiconductor wafers and the like are provided. In one embodiment, a plasma process fault detection module (100) includes a data selection sub-module (101), a model building/updating sub-module (102), a principal component analysis (PCA) analysis sub-module (103), a model maintenance sub-module (104), a wafer categorization sub-module (105), and a data output sub-module (106). The data selection sub-module (101) obtains selected optical emissions spectra (OES) data for each wafer that is processed. The model building/updating sub-module (102) constructs multiple models from the selected OES data for a number of wafers.