# CMAQ-ISAM5.5 how to PM2.5TOT

**URL:** <https://forum.cmascenter.org/t/cmaq-isam5-5-how-to-pm2-5tot/5845>\
**Category:** CMAQ-ISAM\
**Created:** [June 6, 2025, 4:28am UTC](https://forum.cmascenter.org/t/cmaq-isam5-5-how-to-pm2-5tot/5845 "2025-06-06T04:28:32Z")\
**Posts on this page:** 1\
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**Author:** ![hogrefe.christian](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@hogrefe.christian](https://forum.cmascenter.org/u/hogrefe.christian)\
**Post date:** [June 6, 2025, 2:45pm UTC](https://forum.cmascenter.org/t/cmaq-isam5-5-how-to-pm2-5tot/5845/2 "2025-06-06T14:45:12Z")

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Hello @bancheng ,

your image did not upload successfully, but if your question is about calculating PM25\_TOT from ISAM output, the following threads should be helpful. The general approach is to use the `combine` utility and modify the mechanism-specific `combine` species definition files distributed with CMAQ to sum the aerosol species from the ISAM output files for the desired tags.

[Post1](https://forum.cmascenter.org/t/how-to-get-pm2-5-tot-from-cmaq5-4-isam-outputs-by-combine/3831)  
[Post2](https://forum.cmascenter.org/t/in-order-to-track-pm2-5-pollution-sources-which-species-should-be-extracted-from-sa-files/4714)  
[Post3](https://forum.cmascenter.org/t/how-to-calculate-pm25-tot-pm25-concentration-from-cmaqv5-3-2-isam-results/2109/2)  
[Post4](https://forum.cmascenter.org/t/how-to-get-total-pm10-pm25-from-cmaq-v5-4-isam-output/3890)

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