It draws the intake air from the pvc pipes that are vented all the way through the floor from the underside of the camper, the hot air blows out the back through the
refrigerator vent (in the last picture it's hard to see the vent holes in the outside vent from the inside view) where it is sealed off from the intake air coming from below the camper. When the cabinet front is sealed off with trim there should be no inside air being used at all, it doesn't cause any problem now with all the
windows shut, the pvc vents really are providing a lot of outside air and it is pretty cool air because it is shady under the camper and the intake is not close to the exhaust. I hope I explained it OK, holler back if not. Thanks!