From the Summary...'For many projects a simple model often provides as good information as a more complex model. Regulations, however, may dictate the level of modeling required for each project. Other times, community values will determine the level of effort needed to demonstrate compliance or alternatives. Also, skills available to set up and run models or the availability of required input data may affect whether a prediction system is necessary and which one is most appropriate. Because regulations vary from state to state and tribe to tribe and because expectations vary from project to project there is no simple way to determine what dispersion prediction system is best. It is hoped that the information in tables 9.3 and 9.4 can be used to help assess the value of available methods and models. For example, if a simple indication of visibility impacts is required, plume models can be used or visual indexes can be approximated from concentrations out of box, plume, or puff models. If more detailed visibility impacts are required, a sophisticated puff model should be used. Whatever the situation, whether smoke dispersion prediction systems are used for screening, planning, regulating, or simply game playing, it is helpful to remember their strengths and weaknesses.'