It works, but i found it only works out with a room that only has girls that are same or close days in flower and similiar run lenghth. As anectodally i found it necessary to reduce and cut it off at the end for quality sake. Though i have heard others say their experience is opposite, this is mine:
Im off it right now only because i have girls at diff stages in there.
I had run great w co2 from my very first micro grow, because i got the equipment for a song i set it up even for the microgrow as my very first run ever. First run i blew my mentor away. When i moved into a multiple plant grow room, i of course took the co2 to it and went great for a year or so, would run co2 to timed calculated amount to obtain 1500ppm, and heat up to mid to upper 80s and rh 65 or 70 and they loved it!!!! Would do that for say 5 or 6 weeks then start backing all down to finish hopefully last week to week and a half at ambient co2, temps high of upper 70ish lows of 70ish rh 40 to 50
Great yeilds great quality. Then one round a heatwave hit and my enviornmental controls that as rudimentary as they were had worked thus far failed to combat the heatwave and it happened to coincide with the last two weeks of flower... i finished in upper 80s a few days low 90. I kept co2 rolling to reduce that heat stress, being the plant deals better with heat when it has the co2 for turbo mode. The plants looked just beautiful.... the product in the end tho tasted like hay no matter how carefully i cured it. Its effects though there where as short lives as could be. You coulda rolled one in the cop shop and they wudnt have smelled it.
I really think those last two weeks you dont want the plant i n turbo anymore. I gotta get ballanced back out to have same stage girls back in there so i can fully utilize the set up being i added real ac after that disappointing round. Now i could get that insane growth and fullness out of those high co2 high temp and humidity gets ya for the first bit of flower, while getting the quality a cold finish gets ya. Now with the controls i have with ac i finish at 70 high temp 58 low, but even in begining keep her 78ish as high without the co2. Its arguable but many beleive you dont reap all of co2 rewards without increased temp. The purple hues ya get from the cold finish adds real beaity and deapth, the quality is bar none increased from my rounds before the cold finish.
So co2 em! Just back off at end imho...