actually... i just read.. this...

"Some growers add C02 to their grow rooms to increase growth rate. This has proved itself to be effective in many experiments. C02 supplementation also helps the plants withstand higher temperatures of up to 95 degrees without slowing down growth. There have been complaints however, that C02 supplementation during flowering reduces potency. Therefore, C02 should be stopped when the lights are turned to 12/12."