An actual functional hood that has decent CFM and exhausts to the exterior will not need any other type of external ventilation. Perhaps it is a portal for the makeup air that will be needed to run the hood? That is most often ducted to the HVAC area so the air can be conditioned. Or perhaps it's for a energy recovery system tied to your ventilation hood so that you aren't exhausting expensive heated and cooled air into the outdoors.

Talk to your HVAC person and ask them.

A ceiling register over wall ovens power vented to the outside can be useful in removing oven-generated odor, but the MUA system has to be adequate for both it and the hood over the cooktop. In the case of ranges the cooktop and oven are collocated, so just the hood should suffice.

kas

Thanks. I was looking at a 900 CFM hood, and the plan calls for wire and pipe only (modular home), so when I saw this little fan near where the range hood will be going, I wondered what it was, and it turned out to be a dinky little 160CFM fan (I assume one of the old 8" round nutone types.) As I understand it, smell means particles of some sort so I didn't know if this was really for the oven, although it's not quite near it.