Co2

Scenario: because of a cool tube setup and apartment living, constant venting and filtration is a must. This is easily done. However, this makes CO2 enrichment a difficult task.

Question: If my passive vent is on the bottom and my carbon filter in the roof is the suction point, should I route my CO2 dispersal hose at the BASE of the plants rather than the top, in an effort to let the gas pass upward over the plant? Am I pissing into the wind? Please advise.

If you are venting, then yes you are pissing co2 in the wind

How long does it take for CO2 to be absorbed if it's put directly on the plant?

why not suck straight from the vent through the cool tube and out, seal the room and use standalone ac. im not sure how stinky the air the standalone acs put off in there vent though. really without a way to seal your kinda screwed for co2 unless its comming from somewhere it would anyways(tankless water heater).