You still need fresh air coming in but. As I was told by Zandor. C02 can run at higher temps and must be mantained at 1500 ppm's. Then flushed out with fresh air every 4 to 6 hours during light cucle. It is not needed during dark period only fresh air. If you can not maintain 1500 ppm's or close save your self the trouble. It's not worth it.

WARNING Will Robenson, even in a sealed room never and I mean never in a living area that could be contaiminated by Co2. It can flood a whole house and being heavier than air suffacate any people or pets living there.

Other than that party on Garth.