Looking for advice on timing co2 injection and exhaust fan settings.

[Bloomin Idiot]

This is set up in a 4x4 tent. The timer being used allows for 15 minute intervals, so the plan is to run co2 for 15 minutes every 3 hours during lights on. Exhaust fan is responsible for removing heat and filtering air.
Should the exhaust fan stay off after a co2 injection period and if so, how long?
I'm also wondering if the exhaust fan can be cycled on and off during lights off or if it should run continuously?

You can buy a controller to do this. a basic would be something like a C.A.P. air 3.(if you can I would get something a bit better.)