The first thing you'll want to get, after the software, is a User's Guide for SCREEN3. While the program prompts the user for inputs, the guide contains technical information you'll need to understand more advanced features of the program. This site cannot reproduce that information, and is intended merely to get the novice "up and running." The User's Guide is published by EPA's Office of Air Quality Planning and Standards, Technical Support Division at Research Triangle Park, and can be downloaded with the software from the Technology Transfer Network BBS.
SCREEN3 was most recently updated in July 1995, and runs in DOS on IBM-compatible PCs. It is not resource-intensive, but you will appreciate a faster machine for more elaborate calculations.
Screening analysis of air pollution sources is designed to find the worst-case scenario for planning purposes, based on one-hour averages. These conditions may or may not ever occur in reality, but greatly simplify the model. The model is sophisticated enough to handle several complicating factors, including rural and urban terrain, all atmospheric stability classes, varying receptor heights, and the effect of building downwash on a smokestack plume.
SCREEN3 cannot handle multiple sources or predict average concentrations for longer than 24 hour time periods. See the Technology Transfer Network BBS for more information on the best model to use in conditions not covered by SCREEN3.
Once you've downloaded and unzipped the program, you're ready to begin -- simply type "SCREEN3" at your DOS prompt. There is also an example file included. To run the example, type
SCREEN3 <EXAMPLE.DAT
at the prompt. You can run any .DAT file with the same syntax. For example, if you run a set of data and want to change only one or two parameters, you can find those parameters in the SCREEN.DAT file, rename the file as "MYFILE.DAT," change them, and type
SCREEN3 <MYFILE.DAT
to run the program with the changes. It is best to rename the .DAT file after making your changes. If you wish to save the results of a run, you need to rename the SCREEN.OUT file, as the program overwrites it each time it runs.
...move on to learn about Data Needed