How would he plan on dispersing the c02?

Does he run 24/0 or 18/6 Veg? (yes, it does matter when c02 is concerned)

As far as your yield and maturity question, maturity time is based on the genetics of the strain and the environment in general. That basically means if the c02 has a positive effect whatsoever, it will increase the yield even if it's the smallest amount.
(at least this is what this noob has learned, I could be wrong!)
The Grim Reefer Reviewed by The Grim Reefer on . CO2 anyone? I'm hoping someone could step forward and tell me what differences it would make in my pals growroom. He is not computer savvy and asked me to find out. Room is 20x8 with a 7 ft ceiling. It has 4 1000W for flowering. From what I have heard, It doesn't increase yield, it just grows them to maturity quicker. Is that correct? Would the room have to be airtight? Any info will be appreciated. Wallhofen Rating: 5