On September 26, 2019, a major industrial fire broke out at the Lubrizol and NL Logistique warehouses located in the Rouen port area. The fire produced a large plume of smoke for several hours, accompanied by soot fallout and odors that persisted for several months after the fire. A system for the epidemiological assessment of the short-, medium-, and long-term health consequences of this fire was established by Santé publique France. Named "Post-Fire Health 76," this system includes various studies and initiatives, including epidemiological surveillance of the general population. This document presents the first phase of this surveillance. Its objective is to track changes over time in the frequency of health events within the area exposed to the industrial fire in order to detect abnormal increases that could constitute a health signal. It is based on monitoring changes over time in health indicators within the area exposed to the fire and comparing them to those in unexposed areas or a reference period. The area exposed to the fire or its consequences is similar to that of the self-reported health survey "A Study Listening to Your Health" and includes 119 municipalities in Seine-Maritime. The two unexposed areas are located, respectively, around the cities of Le Havre and Caen. Health indicators are calculated using data from the National Health Data System (SNDS). They generally concern healthcare utilization and hospitalizations for various health conditions (such as cardiovascular, respiratory, mental health, and perinatal issues), which will be monitored over different periods depending on the type of indicator. This document presents the methodology implemented to ensure this surveillance.