We are redoing our kitchen and will be installing a 36" gas range. I'm not sure which range yet, but looking at anything from Ilve to Wolf (guessing the Wolf will be out of our price range). Sales rep says we need a make-up air system if we have a hood that is 400 cfm or over. It looks like all the ranges over 30 inches wide are over 400 cfm, and I can't figure out how to make sure we have "make-up air." Any thoughts/ideas/advice to share?