Hi DGC, just giving an update on my little project. I got a 2 x 4 tent where I grow oyster mushrooms 12 blocks (5 lbs each), at the bottom of the tent the CO2 is at 1300 PPM. I have an AC infinity fan that extract the CO2 from the bottom and sent the CO2 to my 8′ x 8′ grow tent. The fan speed is set to 5 (Need the AC Infinity controller 67 to set a constant speed with auto on), but also set to auto, if the humidity is too high the fan will speed up but stay at speed 5 when the humidity is back to 80 %. In my 8 x 8 the CO2 stay between 800 to 950 PPM, the CO2 input is connected to two 1″ pvc pipes, installed on top of my plants with holes. I get more CO2 when the mushroom blocks are fruiting, I also make 4 blocks every two weeks for a constant supply of CO2. I can put up to 20 blocks in my mushroom tent and should get more CO2.