if you want to run with enhanced co2 then you want to create as self-contained an environment as you can. vent the lights with air cooled reflectors using outside-your-room air and duct it through the lights and out of the rooms without mixing with room air. then you need a co2 monitor/controller and either a gas generator or bottled co2. you set the co2 level for between 1,000 and 1,500 ppm co2 and vent only as much as is required to manage temperatures. you're going to want something like a 250cfm fan with a variable speed controller (or better yet a co2 controller that includes ability to manage fans). even better approach to use with co2 is with an a/c so you don't have to vent for temperatures. in that case, you only need to vent occasionally to rid the grow room of excess oxygen.