## Advanced / Configuration Setup / Concentration Packing and Output Units

Concentration Packing Method

CPACK is the flag to turn off (set to 0) concentration output packing. The default is to write the binary concentration file at only those grid points that have a non-zero concentration value (set to 1). Setting the flag to zero results in the output of the entire concentration grid. Due to the nature of the packing method, if the plume covers more than 50% of the concentration grid, the default concentration packing will result in larger output file than an unpacked concentration file.

The Point option (CPACK=2) is a special feature that forces the concentration grid to have a size of one grid point over the location of the center point. It is a way to define a single sampling location.

Concentration or Mass Output Units

The default option (CMASS=0) is to output units of mass/volume. However, if mass-only output is desired, then setting CMASS=1 will cause the model not to divide the grid cell sum by its volume.

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