CCTM also includes a process analysis (pa) module. Process analysis is a technique for quantifying the contributions of various physical and chemical processes, and the changes in the predicted concentrations of a pollutant. Process analysis is useful in the quality control of a model because it separates out the influence of individual processes on the pollutant concentration. With this information, compensating or unresolvable errors in the model or input data can be identified even if they are not reflected in the total change in concentration. For example, if an error in the emission input data caused negative concentration values, it may not be recognized in the predicted concentration because of a large addition in the predicted concentration resulting from chemical processes.

In addition to its role in the quality control of air quality modeling, process analysis is a very strong analysis tool. As a tool for model development, process analysis can help evaluate the effect of modifications on a model or process module. As a tool for regulatory decision making, process analysis can help determine if a decision to control a specific type of emission would produce the desired results, or if another control would be more effective.