When the regional health surveillance and emergency platform receives a report in the occupational health category, it validates and assesses it. If the report appears unusual (clustered cases of cancer, poisonings, industrial accidents, etc.), it forwards it to the Cire. The Cire then mobilizes the GAST, which has one month to validate or reject the report, determine whether to issue an alert, launch an investigation if necessary, and decide, if warranted, on immediate management and prevention measures. In all cases, the reporting party is informed that their case is being handled.

The GAST makes a decision based on the consensus of its members. In particular, it determines whether an epidemiological investigation is necessary. If an investigation is decided upon, it is coordinated by the CIRE in collaboration with the other GAST members, following consultation with the occupational physician and the company representative.

The investigation methodology may be based on the guide produced by Santé publique France: "Epidemiological Surveillance of Mortality and Investigation of Spatio-Temporal Clusters in the Workplace."

By leveraging the complementary skills and knowledge of each of its members in the field of occupational health, the GAST ensures a coordinated, structured, unified, and rapid response to reporting entities at the regional level.

This system strengthens the health surveillance and early warning mission of Santé publique France and the ARS by incorporating ad hoc local expertise in occupational health, such as the Direccte or the CPPs of university hospitals.