Thanx HydroCannabis, yes thats an adaption of a link I found on here, the only thing that was wrong in the info was the claim Co2 is lighter than air. All the info I have read otherwise states Co2 is heavier than air so thats why I hang them. Basically you pierce holes in the top of the bottle tops & make your Co2 mix up in the bottle. You have to watch the mix strength & don't hang them directly over the plants as there is a risk of frothing.

There is a lot of good pro & con points regarding Co2 on threads here in the forums, but the only thing I can say for sure from experience of what I have seen. Is that the Co2 seems prevent the room heating up as quickly. I know this doesn't make sense with regard to the greenhouse gasses debate, but I know my temps stay lower when I am using the Co2.