How can I get results for different averaging periods?


The Screen model only produces 1-hour average results (with the exception of 24-hour estimates for complex terrain impacts), however, scaling factors can be used to estimate other averaging periods.

To obtain worst-case impacts for longer averaging periods, such as 3-hour, 8-hour, 24-hour, or annual, multiply the 1-hour maximum concentration from SCREEN3 by the appropriate scaling factor.

 For example, for an annual averaging period, you multiply by a scaling factor of 0.08 (+/- 0.02) following the EPA document "Screening Procedures for Estimating the Air Quality Impact of Stationary Sources, Revised" (EPA-454/R-92-019, October 1992).

The suggested scaling factors are as follows:

Averaging Period --> Scaling Factor

3-hour --> 0.9 (+/- 0.1)

8-hour --> 0.7 (+/- 0.2)

24-hour --> 0.4 (+/- 0.2)

Annual --> 0.08 (+/- 0.02)

Note: These factors are designed to be a rough guide and are based on elevated point sources

Last update:
2010-06-02 16:56
Author:
Gareth Davis
Revision:
1.0
Average rating: 5 (1 Vote)

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