The present disclosure relates to the manufacture and use of an additive manufacturing (AM) system that employs a spacer flow guide disposed or formed within a housing that defines a chamber of the AM system. The spacer flow guide may direct various portions of a gas flow within the chamber to respective exhaust channels. For example, in combination with portions of the housing, the spacer flow guide may define a main exhaust channel that extends between the chamber and a gas outlet formed in a downstream end of the housing. Additionally, a bypass exhaust channel may be defined between the chamber and a back surface of the spacer flow guide to fluidly couple an upper portion of the chamber to the main exhaust channel.