Ducting is simplest if your range and hood sit along an exterior wall; the duct can run out the rear of the hood and through the house wall. For a range placed against an interior wall, the duct can go up into the soffit above the cabinets or between ceiling joists, and then out through the nearest exterior wall. Regardless of where you run the duct, it is important that it runs all the way to the outdoors; a ventilation duct should never end inside an attic or other enclosed space.