CALPUFF is no longer a regulatory model for the US EPA

calpuff recommended model EPA   The website of the Support Center for Regulatory Atmospheric Modeling (SCRAM) no longer includes the CALPUFF model as a recommended dispersion model. This means that one of the most widely dispersion model used for odour modelling is not recommended by the US EPA any more. This decision has serious consequences for the odour community.

   The U.S. Environmental Protection Agency (US EPA) originally published the Guideline on Air Quality Models in 1978. Since then, a few revisions of the Guideline have been carried out. In 2003, this Guideline was modified to include CALPUFF as one of the preferred model. This model was removed from the "preferred list" in May, 22 2017 (and now from the website). allegedly due to concerns about its capabilities to deal with long-range transportation of pollutants. This is no argument to exclude this model from the recommended list, as it is widely used for other purposes, different from long-range transportation. For example, when dealing with the calculation of the odour impact of a facility.

   The US EPA has a list of "recommended dispersion models" and another one of "alternative models". The Gaussian AERMOD plume model and the CALPUFF lagrangian puff model were included in the list of recommended dispersion models. There is a lot to say about these two lists but, in short, the recommended models were the ones used for Environmental Impact Assessments (EIA) not only in USA, but also in many other countries of the world.

  One of the main reasons why CALPUFF and AERMOD were used all over the world was that they are freely available and open source. Another important reason was that they were recommended by a regulatory administration. There are not many dispersion models recommended by regulatory agencies.

   So, why is the US EPA leaving a more advanced modelling system like CALPUFF out of the list of recommended models alleging "concerns about its ability to deal with long-range transportation of pollutants", when this is just one of the many uses that this model has?

   Maybe one of the reasons is that AERMOD* is developed by the US EPA and the American Meteorological Society (AMS), a public non-profit organization, while CALPUFF is developed by Exponent, a private company. Perhaps the changes in the ownership of the model in the recent years might have arisen some concerns in the EPA. Another reason could be that the leader of the CALPUFF project Joe Scire is unfortunately out of the project, although there is still a great group of people behind the project.

   Nobody really knows the reason for this exclusion based only in one criteria, but this is already bad news for the odour community.


*The name AERMOD is derived as follows: AMS and EPA Regulatory MODel.

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Carlos Nietzsche Diaz Jimenez's Avatar

Carlos Nietzsche Diaz Jimenez

Carlos is the editor-chief of and has been in the odour world since 2001. Since then, Carlos has attended over 90 conferences in odour management, both national and international and authored a few papers on the subject. He has also organized a few international meetings and courses. Carlos owns a small company named Ambiente et Odora (AEO). He spends his free time with his wife and his twins, Laura and Daniel, and of course, writing on

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