The growth rate is not a linear relation to the amount of CO2. although CO2 is very important, it is a factor that is much harder than it seems to control. Most growers us CO2 and don’t get the benefit that they should because of how it is implemented. I have helped many growers to maximize their results by making a few changes in their systems. I recommend using a regulator attached to 1/4 inch tubing. then suspend the tubing just below the canopy of the plants. Have timers set so the exhaust fans and circulating fans are off when CO2 is on, plus about 15 minutes after CO2 stops.
The carbon used in filters is activated carbon. Save a bunch of money and google homemade carbon filters. If made properly they are very good, and you have the ability to change out the materials when they start to degrade. Unfortunately most filters that you buy are sealed units and you can not rebuild them when at the end of their life. There are some pretty neet plans for whatever size grow area you have.
Hope this helps