# Must VOC be included in the emission inventory if only PM2.5 concentrations are simulated in CMAQ 5.3.2?

**URL:** <https://forum.cmascenter.org/t/must-voc-be-included-in-the-emission-inventory-if-only-pm2-5-concentrations-are-simulated-in-cmaq-5-3-2/3386>\
**Category:** CMAQ\
**Tags:** cmaqsmoke, cmaq\
**Created:** [June 27, 2022, 2:39pm UTC](https://forum.cmascenter.org/t/must-voc-be-included-in-the-emission-inventory-if-only-pm2-5-concentrations-are-simulated-in-cmaq-5-3-2/3386 "2022-06-27T14:39:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ghb980003021](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@ghb980003021](https://forum.cmascenter.org/u/ghb980003021)\
**Post date:** [June 27, 2022, 2:39pm UTC](https://forum.cmascenter.org/t/must-voc-be-included-in-the-emission-inventory-if-only-pm2-5-concentrations-are-simulated-in-cmaq-5-3-2/3386/1 "2022-06-27T14:39:28Z")

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Hello everyone.  
I want to use CMAQ to simulate PM2.5 concentrations, can I not enter VOC species in the emission inventory input?  
Will it affect the simulated PM2.5 concentration values if no VOC species are entered in the emission inventory input?  
Thank you for your answer!

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**Author:** ![sergey](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@sergey](https://forum.cmascenter.org/u/sergey)\
**Post date:** [July 5, 2022, 2:40pm UTC](https://forum.cmascenter.org/t/must-voc-be-included-in-the-emission-inventory-if-only-pm2-5-concentrations-are-simulated-in-cmaq-5-3-2/3386/2 "2022-07-05T14:40:58Z")

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I recommend against running CMAQ with an emissions inventory that removes VOC species. In a photochemical model like CMAQ, VOCs play an important part in the chemical interactions between all species and both directly and indirectly impact PM2.5 concentrations.

There is also not much reason to remove VOC species from the inventory. All of the same calculations will still be performed just with using zeros.

Sergey

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**Author:** ![ghb980003021](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@ghb980003021](https://forum.cmascenter.org/u/ghb980003021)\
**Post date:** [July 6, 2022, 3:02am UTC](https://forum.cmascenter.org/t/must-voc-be-included-in-the-emission-inventory-if-only-pm2-5-concentrations-are-simulated-in-cmaq-5-3-2/3386/3 "2022-07-06T03:02:01Z")

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Thanks to your suggestion, I ended up entering the VOC emissions inventory in CMAQ.