Which are the basic elements within a PEMS? In order to deliver a complete PEMS application, it is necessary a PC (typically a Server, but also a laptop could easily cover all the requirements) hosting IMP On-Line. The PC must communicate with plant DCS or historian to gather input values needed for emission estimation and to write predicted values. The other crucial component of PEMS installations is Inferential Modeling Platform, the software toolkit that runs the models and provides the estimation of emissions. Depending on the application, a Data Acquisition System (DAS) may be required: for typical applications where PEMS are used as a backup of CEMS, the DAS of the existing Emission Monitoring System (EMS) can be used. ABB has the experience and the know- how to properly realize any customized configuration