France has several monitoring systems that form the foundation of its health safety surveillance. This system is designed for the early detection of signals and their swift into an action system that enables timely, appropriate, and effective interventions to protect public health. These signals are considered alerts when sufficiently validated after an initial risk assessment and if they represent a potential threat to public health, necessitating an appropriate response. The French Addictovigilance Network (FAN) was established specifically to address complications associated with the use of psychoactive substances (PAS), both medicinal and non-medicinal, excluding alcohol and tobacco. This system, unique in Europe, provides information on one of the most complex vigilance systems due to its scope, and the risks associated with it are becoming an increasingly significant public health issue. FAN is at the forefront of identifying potential signals. It has been working closely with regional partners since 1990, particularly through a multi-source approach that combines data from various sources, in collaboration with local professionals. After outlining the missions of the addictovigilance centres and the general principles of signal detection in addictovigilance, this article will present recent examples involving similar products but different identifications or modes of consumption: synthetic cannabinoids, nitazene, pregabalin, methylphenidate. These examples demonstrate that while there are regional disparities, the risk of occurrence in other French regions should not be overlooked, and information should be rapidly communicated at the national level for preventive action.