usually, carbon filters exhaust to the outside to get rid of heat and humidity. exhaust and intake fans have to be shut off while co2 is being injected, or it will just be exhausted out of the room. you have to be able to keep the heat and humidity down in the room while the fans are off.
That is kind of pushing it. CO2 totalling at 2,200 is a maximum limit that is adding lets say 1,200 ppm you introduce and the approximate amount you are bringing in in the form as an intake coming from outside sources. Of course that is dependant on the amount of cfm going in and going out. Just be sure when introducing CO2 as an enrichment that your lights are or have been on at least 1 hour because the stomata have already been open to take in the supplemental CO2.
yes, you can use an air conditioner to control the temps and humidity in a sealed room, but your co2 calculations will need to be a little different. you would be supplying 100% of the co2 at all times, not just supplementing now and then when the lights are on.
the plants don't need much while it's dark in the room. they might use a tinny bit but it's never anything to worry about, and whatever is left over in the room from when the light is on would be more then enough. what I meant was, say the lights just came on, but normally the co2 wont come on for another 3 hours or so. the room isn't getting any co2 from nature from the intake vent, so it has to be supplied by you. what I meant was, your calculations have to reflect this, 100% of the co2 the plants use will be coming from you, so there's no 1200+300