Hey @wallen ,
If I can suggest a good place to start with the EMS, try exporting your model with an AFN using the HB Airflow Network component. When you use the AFN in Honeybee, you’ll see that the resulting OSM/IDF has an EMS program within it, which is used to open and close the windows of the AFN based on the logic that you specify with the HB Ventilation Control component.
So, if you can understand this basic EMS program that opens the windows based on the room air temperature and (optionally) the schedule you apply with HB Ventilation Control, you can edit the EMS program to also have logic based on the CO2 sensor that you place in the room.
Or, yea, if the schedule in the Ventilation Control already gives you what you need to model CO2/occupancy related phenomena, then use that.