Do you need circulation fan with co2 enrichment?

im thinking about getting a co2 tank for my 2 400 watt grow. looking to expand in the future and am 3 weeks into flowering and want to maximize this yield. I dont currently have an inline fan but have a lot of extra space and a vent where cool air makes its way in. room from 80-85 with lights on so heat is not a problem but the plants arent getting enough co2 from stagnant air. wondering if i can run a co2 tank without an inline fan for room circulation and if that would be ideal.

as long as its not leaking out anywhere i think it would be fine..iv seen people run the co2 tube behind a wall mounted fan as opposed to the poking holes method that seem to work pretty good.

so if i add co2 i should cover the vent? so i wont need to replace any air in the grow room if im running co2?

no not at all unless you have a bad heat problem..the co2 will substitute for the "fresh" air and your plants can actually run a bit higher temps with co2 enrichment

CO2 enrichment you want a air tight sealed room. i would make sure you have plenty of occilating fans to keep air moving in the room and a split system A/C to manage your humidity and keep temps down