AERMOD — The Complete Guide: Free Air Dispersion Modelling for Stacks and Area Sources

AERMOD is an air dispersion model from the US Environmental Protection Agency (EPA), and one of the best-known models worldwide for assessing the impact of stationary emission sources. It is in the public domain and completely free — both the source code and the executables — and the method applies anywhere, provided you supply local meteorological and terrain data.

AERMOD

US Environmental Protection Agency

An air dispersion model for stacks and area sources: ground-level concentrations around industrial plants, used worldwide in environmental impact studies.

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What you get

Source types — stacks (point sources), area sources and volume sources.
Meteorology — hourly weather data processed by a dedicated preprocessor.
Terrain — accounting for ground elevation around the source through another preprocessor.
Building effects — downwash of the plume caused by buildings near the stack.
Results — average and peak concentrations for different averaging periods on a receptor grid.

What to know

AERMOD is a command-line program: you write a text input file, run it and read an output file. There is no official graphical interface, so the work requires familiarity with the input structure and the preprocessors. Preparing the meteorological data is the hardest part. Check what your local regulator requires regarding the model and data before you start.

Related tools

For air trajectories and regional-scale dispersion — HYSPLIT. For emergency release scenarios of hazardous chemicals — ALOHA. For mapping the concentration results — QGIS.