You mean a room like this?
for 6 hoods you are going to need 18k BTU AT a MINIMUM. I would highly suggest a 24K unit if it gets hot in your area. That room you see is fully sealed with a water cooled co2 burner, two 60 pint dehu units, and a high quality 6" fan on each side pulling air through the hoods. Carbon scrubber in the corner but I only run it about 1 month per cycle.If your asking yourself "do i need to get rid of stale air" I think you may want to up your plant and indoor growing knowledge before making the plunge to a sealed co2 room. When done right, ITS BANGING. When not done right...well, its a half assed waste of money.