While you may get decent results by running CO2 and not ventilating your sealed room, you will hit less weight than if you had properly ventilated as well. The key is to maintain your CO2 levels but slowly vent out the air with a continuous exhausr fan using a dimmer controller or by exhausting every few hours for 10 mins. You must rid the bad gases that form in a sealed room especially if you are burning CO2. You may spend a little bit more on CO2 but the extra weight from the bigger buds you will get trumps that cost.
Here is why: Because of a plant biproduct and burn biproduct gas called ethylene. Ethylene known as the death hormone acts at trace levels throughout the life of the
plant by stimulating or regulating the ripening of fruit, the opening of flowers, and the abscission (or shedding) of leaves. Excess ethylene will cause your buds to rippen faster in the last few weeks and will stunt your bud growth. Dying leaves in the last few weeks produce ethylene. Burning CO2 creates ethylene as well.
Plants consume CO2 in the process of photosynthesis and convert it to sugar. Oxygen is a waste product of this reaction, in that water is split to form hydrogen and oxygen. The plant uses the hydrogen to produce ATP. This process is only occurring in the day when there is light. However, at all times, the plant is respiring, just like people. They need oxygen for the metabolic process and produce CO2 as a waste product. Indoor closed grows also produce
Ethylene . This is a plant hormone in a gas form that can have negative effects on flowering plants { specially when the plants are closer to finish]. Any dying and decomposing plant mater can produce Ethylene.
Ethylene damage can be hard to see if you dont know what your looking for and can have very negative effects on your yield .Its nice to shut down the ac at night and flush out all contaminants and start fresh every morning. Some people have good success periodically flushing out there rooms of co2 during the day. There is also some discussion out there regarding stimulating the stomata of the plant to open fully after they have slowly been closing and becoming small from large quantities of co2 in the air. But there is a certain logic to it. [why open your mouth wide if you only need a small breath]. personal preference is the answer you seek ,theres no one way of doing anything
http://www.growerdirect.com/flower-care-ethylene-gas
