In zipper pouch production, the most under-specified subsystem is the fill-zone air management—and it is the one that most directly determines whether the zipper closes on a clean track. Powder and fine granule products generate airborne dust during the filling drop; that dust settles on the zipper interlock and on the film surfaces that will later be sealed. The zipper may close mechanically, but the interlock is contaminated, and the pouch fails a leak check at the customer