I see. So the water stays in the tank and gets heated and the CO2 shoots out into the tent. And that one tank allows you to maintain 1200 ppm? Why is it only when the light is on? (oh, duh, no point to run CO2 in the dark, right?). Wow. I'm jealous, lol. I don't think my two CO2 Exhale bags are getting my tent to 1200. Lmao. So what do you find the biggest benefit of the CO2? Better growth in veg? Bigger and better buds? Did it make a difference when you first installed it within a day?When you burn propane, the by-product is H2O and CO2. This is just an outdoor camping tankless water heater where I run the water in a circuit. It is activated by an inexpensive CO2 controller and fires off for about 3 minutes every 30 minutes to keep my 10' x 10' lung room @ 1200ppm (only when the light is on).