just now doing similar co2 newbie install....don't/can't have sealed room....
392 sq ft ......flower room open around top/poly enclose......exhaust 6" vortex @ top o room for heat/smell......tank +reg w/co2 rings above 2 1k hps....
am i spinnin my wheels tryin to get/keep co2 in there?......no meter yet/$
...but soon....ambient levels @ 500ppm/with test tube tester dealy....typical temps 75-85...flow rate @.4cu ft ?..30 min drop at 6a.m....15min drop every/hr till approx hr before bedtime......synched drop/exhaust...girls had an immidiate improved look overnight......but tips appreciated......smoke up