homebox,cooltube,ballast and ventilation questions

[Tater]

If I were going to run CO2 I would have a totally sealed grow environment. No air in, no air out. The only time my room would vent would be at lights out to bring the CO2 ppm back down to 800. Other than that the PPM would be kept at 1500 with lights on at all times with no fresh air. As far as hot air pockets, just because you don't have an intake and exhast doesn't mean that there are no fans in the room moving air.

And your right CO2 isn't necessary with good ventilation, but neither are high quality 3 part nutrients, metering equipment, etc. Its not about necessary, more about optimal.