Well the easy way is to use a controller. You set your PPM and then set the exhaust cycle. The controller does the rest.
If you like 1800-PPM total, (room air is about 300-ppm so adding 1500-PPM to reach the 1800 number. You can use timers you just need a few of them.
Some will run the CO² generator 10 min to reach the 1800-ppm every hour and 1/2. You remove the air about 10 min before you turn the CO² back on and start all over again. The best way to vent is to use 2 motorized dampers so your carbon scrubber can put the scrubbed air back into the room or exhaust it out of the room. Depending on the cycle it's set for.
Example:
8:00 am lights on CO² running.
9:30 am switch the dampers from returning the scrubbed air back into the room to vent to the outside.
9:40 switch the dampers back so the air returns back to the room.
9:41 turn CO² generator on
9:51 turn CO² generator off
11:21 exhaust again and start all over.
The AC deals I hope you have will deal with the heat because you can't bring in fresh air and exhause all the time to keep the temperature down. Fans move the CO² around and the idea is to fill the whole room not just one area. The plants take what they want. The plants will use up what they want so don't to much worry about over dosing them on CO² it takes a lot to do that. You do need to play with your timer settings and know your plants and room.

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Peace
Zandor

If you go cheap you grow cheap. - Me