Clear access routes into and out of chemical zones used to avoid contamination are called

Access Control Points

They are restrictions points that enforce regulations and guidelines on decontamination when exiting the sites and ensuring adherence safety standards when entering the site. The regulation are usually, as standard practice, conspicuously posted at the Access Control Points.
Access Control Points are usually set up at the periphery of the Exclusion Zones, and ideally, there should be a separate entrance and exit Control Access Point.