Hi doco
Are you trying to cool the light with the air in your grow room?I think the heat
from the light is too hot to blow in to the carbon filter.You want the air in the room to stay the same temp.the carbon filter is too take the smell out of the
grow room.One fan for the light and one for the carbon filter.
The set up in the drawing is not right A. or B.The fan blows air in too the carbon filter .In your drawing B.cut the carbon filter off and you can cool the light and exhaust the heat out of the grow room.Hook up a fan to the carbon filter sucking the air in the room into the filter back out in the room.This will lower the smell in the room.Thats how it works two fans.