When there is insufficient information about a release to estimate a source term, a nominal unit release of a generic "particulate matter" or "gas" may be simulated. A time series of plots (see example below) shows the predicted downwind location of the plume and relative air concentrations based on the evolving meteorology." For particulate matter, a plot showing relative levels of ground deposition also is provided. Contours are shown in shades of gray to indicate that the source term is unknown and health effect levels cannot be estimated.
