# How to identify O3 formed from NOx sensitive and VOCs sensitive in CMAQ-ISAMv5.3.2
**URL:** https://forum.cmascenter.org/t/how-to-identify-o3-formed-from-nox-sensitive-and-vocs-sensitive-in-cmaq-isamv5-3-2/1932
**Category:** CMAQ-ISAM
**Tags:** admin
**Created:** [November 25, 2020, 12:19am UTC](https://forum.cmascenter.org/t/how-to-identify-o3-formed-from-nox-sensitive-and-vocs-sensitive-in-cmaq-isamv5-3-2/1932 "2020-11-25T00:19:02Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Ryan](https://forum.cmascenter.org/u/Ryan)
#### Post date: [November 25, 2020, 12:19am UTC](https://forum.cmascenter.org/t/how-to-identify-o3-formed-from-nox-sensitive-and-vocs-sensitive-in-cmaq-isamv5-3-2/1932/1 "2020-11-25T00:19:02Z")
Dear staff,
I am wondering whether I can identify O3 formed from NOx sensitive and VOCs sensitive in CMAQ-ISAMv5.3.2. In other words, I would like to know the relative contribution of O3 formed under NOx and VOCs sensitive, respectively. Do the following settings for ISAM support this?
Any suggestions are highly appreciated!
@sergey
TAG CLASSES |Ozone
TAG NAME |N1
REGION(S) |EVERYWHERE
EMIS STREAM(S) |GRIDDED\_EMIS1, PT\_EMIS1
TAG CLASSES |NITRATE
TAG NAME |N2
REGION(S) |EVERYWHERE
EMIS STREAM(S) |GRIDDED\_EMIS1, PT\_EMIS1
TAG CLASSES |VOC
TAG NAME |N3
REGION(S) |EVERYWHERE
EMIS STREAM(S) |GRIDDED\_EMIS1, PT\_EMIS1
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### Author:  [@sergey](https://forum.cmascenter.org/u/sergey)
#### Post date: [December 8, 2020, 10:34pm UTC](https://forum.cmascenter.org/t/how-to-identify-o3-formed-from-nox-sensitive-and-vocs-sensitive-in-cmaq-isamv5-3-2/1932/2 "2020-12-08T22:34:50Z")
Hi Ryan,
I apologize for the delay in the response - I have been neglecting checking the forum.
The ISAM model drastically changed in the latest release. The ISAM control file you provide will not work in the current version for 2 reasons.
1. You specify the TAG CLASSES only once for the entire simulation. Something like this:
TAG CLASSES | OZONE, SULFATE, AMMONIUM.
2. In your tags, you are tracking the same 2 files (GRIDDED\_EMIS1 and PT\_EMIS1) 3 times. This will cause a mass imbalance.
If you would like to track ozone formed from VOC separate from ozone formed from NOX, you need to split that in your emissions files. It would be very easy to use combine or some other utility you like to have GRIDDED\_EMIS1\_NOX, GRIDDED\_EMIS1\_NOTNOX, PT\_EMIS1\_NOX, and PT\_EMIS1\_NOTNOX. Then you can track contributions for the TAG CLASSES = OZONE and provide only 2 TAG NAMEs (one with NOX and one without NOX).
Sergey
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### Author:  [@Ryan](https://forum.cmascenter.org/u/Ryan)
#### Post date: [December 8, 2020, 10:48pm UTC](https://forum.cmascenter.org/t/how-to-identify-o3-formed-from-nox-sensitive-and-vocs-sensitive-in-cmaq-isamv5-3-2/1932/3 "2020-12-08T22:48:21Z")
Hi Sergey,
Thanks a lot for guiding me in the right way. I will try following your suggestion.
Have a nice week!
Regards,
Ryan