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Air Modelling

by Shoeb
(Dhaka, Bangladesh)

Air dispersion model sketch

Air dispersion model sketch

Q: I need help with air modelling. I want to model air pollution at a point surrounded by several stacks. What will I do and how? Please help.....

Barry's Response - Shoeb:

You can download a model called ISC3 or ISC3prime at https://www.epa.gov/scram/air-quality-dispersion-modeling-alternative-models. It has a simplified version called SCREEN3.

I still like SCREEN3 for quick assessments in early design stages of a project, even though it is old and no longer recognized for official purposes. I recommend it for students, new users, and for people who do not have a lot of expensive data on hand. You'll learn the basics and have fun.

EPA's SCREEN3 model estimates air pollutant concentrations downwind of a point source like a chimney or stack. It helps evaluate air quality impacts from new or modified sources, including ones that need permits.

SCREEN3 estimates air pollution concentrations at receptors downwind of the source using a Gaussian dispersion model. In order to predict pollutants' dispersion in the atmosphere, the model takes into account weather conditions, source characteristics, and topography. This model is convenient because it uses theoretical weather data instead of observed hourly weather data.

Typically, SCREEN3 is used in the early stages of an air quality assessment to estimate potential impacts on air quality. Other models like AERMOD can be used if you need a more detailed analysis.

SCREEN3 is free to use, and the EPA provides technical guidance and training. Also, the agency provides software tools and resources to help users input data and interpret results.

Buildings on an industrial site can cause downwash, when a building causes a localized increase in pollutant concentrations on its downwind side. This happens when air is forced over a building, creating a low pressure area behind it. If there are buildings near your stack to consider, download the BPIP or BPIPprm programs from this same site and learn how to include its results in your modelling.

Building Downwash

Set up your stacks and points
of interest (receptors) in the appropriate places

For higher-level models like AERMOD and CALPUFF, you need a meteorological data set. It should be for the area where the stacks are.

Dispersion Modeling for Regulatory Purposes - Both AERMOD and CALPUFF estimate air pollutant concentrations and impacts from various sources, like industrial facilities, power plants, and transportation. Costs and time can vary depending on several factors, including the complexity of the input data and the size of the study area. Here are some general observations:

- Due to its simpler modeling approach, AERMOD is generally faster and cheaper than CALPUFF. Aermod is a Gaussian dispersion model based on emissions rates, stack heights, and meteorological data. It usually takes less time to set up and run than CALPUFF.
- On the other hand, CALPUFF is a Lagrangian dispersion model that can handle more complex terrain and meteorological conditions, so it's better for studies that involve larger study areas or complex terrain. The complexity comes at a cost - CALPUFF takes longer to set up and run than AERMOD because it requires more input data.
- Both models require expertise to set up and run, and you've got to make sure the input data is accurate and up-to-date. Costs can also vary depending on how complex the study area is.

Generally: While AERMOD is generally faster and cheaper than CALPUFF, the choice depends on the specific study needs and study area complexity.

If you need to see one for a good example, you can download one from the government of my region. See https://www.stuffintheair.com/air-quality-dispersion-models.html and select one. The standard in most jurisdictions since 2010 or so has become AERMOD and/or CALPUFF, for considerably more sophisticated air modelling.

Have fun with this.

Professional Air Quality Dispersion Modelling - In the event that you require these results, but the air modelling becomes too complex for you to undertake, please email info@calvinconsulting.ca for further assistance.

Search this site for more information now.

Comments for Air Modelling

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by: kapol

I think you have got the exact answer for you doubts and the question that you have asked was very relevant according to the circumstances. I didn't know much regarding air modeling, but after visiting this blog I think I have got some important points.

Barry's Response - Thanks K, glad I could help.

by: debasish

please guide me how i will prepare a model for air pollution for a mines. i have taken 10 samples with in 10 kms, it is ahilly mining with a predominant wind direction north east .

Barry's Response - Go to the US government SCRAM site and download SCREEN3 for air pollution modeling:


Assume the mine opening is a smoke stack with zero height, its actual diameter and room temperature. See if you can guess at an emission rate for the stuff you are concerned about (such as dust, coded as PM). Play with it a while and see what you get.

Air modelling
by: Anonymous

It a shame that air modeling wasn't more used throughout the history as acid rain was result of lack of it. good answer barry!

Barry's Response - Seems to be getting more well-known these days.

good resources
by: Anonymous

I think you answered her question and provided her with some good links. It is a very interesting question and I was interested to read your answer.

Hope the project goes well!

Barry's Response - I try to help when I can.

Will it work?
by: Anonymous

The design did not look attractive and convincing at the first impression.However hope you get some information soon.

Barry's Response - This is an old website. The original design (for which some elements are still in use) was from March 2003.

by: Steve Dave

My initial impression wasn't a good one. The first thing I saw was what looked to be an MSPaint drawing. Then I noticed the strange pattern on the banner. Then the poor quality of the buttons on the left. The poorly-placed Google Ads distracted from the text, as well. It all immediately drained any interest I might have in the website. I am far from motivated to browse the rest of the site. If I were, however, to search the site, I would hope that the other pages, if not of a better quality, were concise and well-laid out to get across what they needed to before my interest further waned.

Barry's Response - Some of us are scientists, some are web-designers. We all have our capabilities.

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