Can ISAM only track O3?

Hello CMAQ stuffs,

I’m running a ISAM case for ozone source apportionment, but all NITRATE species and VOC species(which I don’t need) are included if ‘TAG CLASSES’ is set to OZONE. This really push the computer memory to the limit so that I have to split it to run multiple times, which cost so much time.
Is there any ways to only track O3 for ISAM?

Yunqing