SCREEN3

SCREEN3

BREEZE SCREEN3, an air dispersion model designed for analyzing single-source release scenarios in simple or complex terrain. SCREEN3 enables users to prepare an initial screening analysis to establish a conservative or worst-case estimate of short-term air quality impacts from a specific source. If predicted screening concentrations are under the level of concern, generally no further analysis is required.

Many states and EPA regions prefer the use of SCREEN3 because of the wide variety of scenarios the model can analyze. These scenarios include:

Sources: SCREEN3 is designed to model single-source scenarios. Point, area, and volume sources, as well as release from flares, can be analyzed.
Terrain: SCREEN3 can model flat, simple, or complex (above stack height) terrain, or a combination of simple and complex terrain.
Receptors: SCREEN3 allows for both automated receptor arrays and discrete receptors to be used in a model run. Discrete receptors can be entered with a height above ground level (flagpole receptors), except in complex terrain situations.
Meteorological Data: A matrix of 54 combinations of wind speed and stability class can be analyzed in a single model run to determine which meteorological conditions produce highest downwind concentrations. Discrete wind speed and stability class categories can also be entered directly into SCREEN3. For complex terrain analyses, SCREEN3 uses VALLEY screening conditions (2.5 m/s, F stability class).

In addition to the above scenarios, SCREEN3 has the ability to account for the effects of building downwash and can calculate concentrations in building cavity regions. SCREEN3 is also unique among EPA models because it can incorporate the effects of inversion break-up and shoreline fumigation.

John Tatom 256.327.3392
jtatom@apt-research.com

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