I had a friend that spent several hours a day in their greenhouse playing guitar. The resulting plant was a thai-Afgani that reached 7' wide and got to 5' plus tall.

I think I am going to hire a day worker to drink beer in my grow room. His c02 rich breath coupled with his almost pure c02 burps should do the trick.

Kidding aside, I use a tank with a steady bleed of c02 and constant exaust with a circulating fan to mix it up. At very minimum you may want to get a regulator and flow meter so you know how much is going into the room. Of course they arn't cheap.