When you pull to much air out of your space, it causes a negative pressure in the grow area.. If your exhaust is 4 or 6 inches and your space is like 5x7 you would need a 6 inch intake to level the pressure out.My 465 cfm fan would raise the floor up when I turned on the fan. It was sealed that tight.I had a four inch intake.. Changed to a 6 and all is well...:thumbsup:


Ga Grown!