Portions of Windermere, Cooper Village, and Deptford Memorial Park were included in the zone.
Officials said a chlorine cylinder within a Deptford Twp. Municipal Utilities Authority (MUA) facility, at S. Delsea Drive and South View Avenue, experienced an active leak.
The Deptford Fire Department and Gloucester County Hazmat responded to the scene.
Officials say crews mitigated vapors with water suppression while conducting air monitoring in the area.
The NJDEP also assisted with containing the leak.