Having your system with no In or out vents (totally contained) is what is referred to as a "perfect room". There are some different approaches to this, and most people who do it, have a CO2 system with a meter to read the PPM. Their system also responds to that reading and releases CO2 if it drops to a certain PPM. Ideal PPM is like 1500. The natural air just floatin around has 200-300. My question is this: Without a way to regulate your co2 PPM, what is your plan? Explanation of the question: You have a a loop system driven by an inline fan of some sort. Inside the loop there is some Dry Ice. I get the approach of bringing the hot tent air through the Dry Ice chamber and give it a little freshening up. Here is where I dont know the numbers, scientifically, but, you could potentially get in trouble here. I dont know how much PPM that is going to put into your system, but you have a chamber with dry ice that is melting (releasing co2), and a fan constantly blowing that oxygen enriched with co2 into your tent. You might get your levels way too high and you can stunt growth. It might not be at a level where its an issue, but it might be. Just thinking you should maybe check it out.