Quote Originally Posted by Orzy
When dealing with passive intakes you don't really need to worry about "negative pressure". As long as your intake is about twice the area of your active exhaust you'll be fine. Some people make their passive intakes a fraction of the size of their exhaust with the idea of negative pressure, but all they are doing is limiting the power of their fans.
He said he had an "intake fan" That is an active intake.

He did not mention having any type of active exhaust.

Active intake + passive/no exhaust = positive pressure

Hopefully he will get an active exhaust for this next grow.