CGE co2 questions

hi everyone, I'm running a closed grow environment it has

-2x1000w sealed vented lights
-70lb carbon filter
-air conditioner
-c02 tank with reg and solenoid valve
-30 girls

my question is if my room is sealed and temp is no problem to control with the vented lights and a/c unit how often should i top up my c02 levels? to bring my room up to optimum i run my c02 tank at 15cfh for 4 minutes. if only my girls are absorbing the gas how often on average would i need to refill my room on average for small plants in veg and on average for big plants in flowering? Also is there anything i'm missing for a complete closed grow room other than the a/c, scrubber, and co2, would i ever need to exchange the air or just keep recirculating the same air the entire grow?

Closed loop control. Anything other then that is just a swag.
There is a stickie
https://www.rollitup.org/indoor-growing/28289-c02-calculator-calculate-how-long.html

that should put you in the ballpark.

As to how often, big plants will use up more then little plants. Its too diverse a Q.

Once again, closed loop controller.

ya i was hoping to stay away from a controller till the next time so i can get a good one there just so damn expensive , the calculator i've used thats how i know 4 minutes at 15 cfh will bring me to optimum. I had a feeling it would be a question with no real answer but if someone has a rough estimate it would be appreciated untill i can get a controller

thanks