Not one bit of mold BleassedinWashington. I have a 8 inch inline fan an carbon filter to match. I use a 6 inch inline fan for ventilation and passive air intake and 4 15 inch fans and a 12 inch fan. I was able to keep the RH at 40 % on average which helped a lot I will never try 23 plants again 15 to 18 at the outside most