Model Change Bulletin

                                 MCB #5

                          TSCREEN (dated 92334)

This Model Change Bulletin documents the revisions to the TSCREEN model
(dated 92334).  TSCREEN, a model for screening toxic air pollutant
concentrations, is based on the release scenarios and methods described in
"Workbook of Screening Techniques for Assessing Impacts of Toxic Air
Pollutants," EPA-454/R-92-024.  Both TSCREEN and the workbook have been
significantly revised from the earlier version.  These changes include
revised methodology, additions of new scenarios and model; thus the entire
model must be downloaded, and the previous version deleted.  In addition, the
workbook has now been written in Wordperfect 5.0 and can be downloaded also.
Users who do not wish to download the workbook text files can still purchase
this document from the NTIS.

The TSCREEN model has been zipped in 4 files for convenient downloading.
These are TSCREEN1.ZIP; TSCREEN2.ZIP; TSCREEN3.ZIP; and TSCREEN4.ZIP.  These
are the executable files that are necessary to run the model.  Some users may
want the model source code as well, and this file is called TSCODE.ZIP.  If you
wish to download the workbook, you should download the following files
beginning with TSCRD1.ZIP, TSCRD2.ZIP, ... etc. 

After you download the 4 executable files, copy them on a subdirectory, and the
type TSCREEN.  The program pop-up menus will appear, and you are on your way.

Due to the major revisions in the model, ambient air impact may be different
than that obtained from the previous version of TSCREEN.