I don't know the best answer for you, but here are a couple of things to consider. A single 2X2ft plant can use C02 at 1500ppm in a 4x4x8 ft space, if it is a sealed room.
Dry air (and in most indoor grow rooms) contains roughly (by volume) 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide. (this is more or less at sea level and 70 degrees F)
At standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m3. That is about 1.5 times the weight of the air in your grow room air.
So you should consider distributing your CO2 from the highest point in your room directly over your plants because it is so much heavier than air. Just make sure the hose is not close to your exhaust-pull-fan because you’ll suck out all of your precious CO2! Another thing to consider is that you are probably bumping your CO2 rate by volume to close to 2000ppm. This adds about 5 times the amount of Carbon and Oxygen atoms into the air which is now the equivalent weight to a strand of hair falling through air.
So I don’t the physics will allow a passive-recirculation system, especially if the room is larger than what a 4x4x8 space can naturally use with (5 or 6) plants.
You could consider a simple oscillating fan at the lowest point in the room at the base of your plants and some duct work to push any unused C02 to the other side of your room. But your best bet is what I ended up doing and just regulate 2 bottles (one in each grow room) Yes – it’s expensive but I’ve seen way too many grows with week CO2 yield only 2 or 3 Oz per plant. And seen one plant (white widow) produce over 1lb. (dried) when the CO2 is dialed in. Also remember that at over 3000ppm your CO2 can be toxic to your plants. And if you for some reason you push more than 10,000ppm in your sealed grow space you’ll get one hell of a headache and maybe even pass out!