wow...this has to be the silliest question i have seen to date on rollitup.org To answer ur stupid ass question, there is absolutely no friggin way to use c02 outdoors. No one in the History of outdoor cannabis cultivation has EVER made ANY mention of using a c02 supplement!! I can't believe ur even asking such a question....Think about it, how in the hell would one use c02 in an outdoor set up???? It's a mind boggling question that literally hurts my head every time i think of said question ...U might as well be asking, how do i hook my 1000 watt ballast up to tree, so i can grow out doors with an indoor light and the tree is powering it with the force of mother nature.. Ur question is That stupid....