Circulating CO2

I was reading about the perfect grow enviornment. while reading through it said that if you have a constant temperature that is not increasing, a constant humidity level, and co2 input you would not need exhaust for your grow room.
My question is how long does co2 stay active? when does it get to the point where youre replacing the co2 instead of adding on to it? i am trying to keep my heat up due to the fact i am not able to use a heater because i dont have enough watts. thanks for any help. SC

Hey SC Your post is a little confusing but I'll give it a shot...

Co2 never goes bad or stale..it is simply diluted or converted by your plants into O2.
You are in a pretty good position if you need heat. Co2 burner for sure. I was just looking into a natural gas unit for when I get a greenhouse. I would love to tap off my utility gas line and not have to go to the store to get refills.

here is a link I was just reading into. i like the remote burner scenerio...

Peace friend...http://www.hydroponicequipment.com/infopages/co2.shtml

OK, the rate at which the CO2 will dissipate can really only be measured by a CO2 sensor because everyone's room will have a different level of seal or air tightness and even if we had the exact same dimensions in our rooms, we still have different things like texture of wood, insulation, outside paneling and all of these things can contribute to the way the flow of air is retained or released from your room. When you have a good CO2 controller it will have a sensor that pumps out more CO2 as it drops below the target PPM level so it can be maintained at that particular PPM.
Though some growers don't exhaust the room, many still have an active intake to bring fresh O2 into the room for when lights go out and because you don't want to be in your room with 1500 PPM of CO2 for a hour or you might not feel too hot. Also you really want to have some O2 in there when the lights go out because that is when the plants are taking in O2 and using the stored CO2 for internal production and the O2 from the room will help them to use that stored CO2. Hope that it is not too confusing and hope this helps some.
Adieu