setting up my exhaust system
 

I need a little help wrapping my head around the exhaust manifold system for my shed. I want to use inline fans/ducting to cool my hoods, and also exhaust the the ambient air through a carbon filter to cut down on smell. Do I even need to exhaust the air cooling the lights out of the room, or can I just have a blower/fan recirculating air w/in the room for that?