Using dispersion method, you are purifying the air. I think it is the best idea, but the contaminants of this purified air should concern.
Barry's Response - Correct you are. I take this to mean that you concede that modelling provides a way for plant designers to determine whether their design will have a problematic impact on the immediate environment, thus providing an opportunity for them to modify the design to achieve a better result. Many times this may take place without reducing emissions at all, and in terms of larger, even global, environmental impact, such a redesign provides no improvement whatsoever.
That is correct; the model does not result in less emissions going to the atmosphere (by default, anyway) just engineering the releases so that they do not severely impact the ground in the immediate area. Sometimes the only solution to a site's problems is to reduce the emissions, but not always.
The response to this is that the regulations concerning the plants for which this type of modelling applies are ones whose local impact is of real concern. In my clients' industries and jurisdiction, this includes sulphur dioxide (SO2), nitrogen dioxide (NO2), particulates (TPM and PM2.5) and about a dozen others on a less frequent but still regular basis, and several dozen others on an occasional or very rare basis.
I have never used it for carbon dioxide, and don't think I ever will. The model does not address global impacts and neither does this specific set of regulations. And that's the scale CO2 affects.