In the workshop producing fluorine/nitrogen mixes at a factory working for the nuclear industry, a leak occurred in the packing station while automatically filling 2 cylinder racks with a fluorine-nitrogen gaseous mix containing 10% fluorine. The technician stopped the compressors feeding these cylinders once the HF detection alarm had been activated (threshold: 2 ppm). The contents of 2 racks were then deviated towards other racks present within the facility. Absorbed by the packing station ventilation unit, 2 kg of fluorine discharged into the workshop atmosphere were subsequently released into the environment via the factory’s main chimney. According to the operator, average concentration in the chimney had remained below the threshold listed in the Prefectural authorisation order. Upon investigation, the leak stemmed from a compromised coupling on a cylinder within the particular rack due to poor clamping of the valve nut. This rack had undergone hydraulic testing at another company where the cylinders were evaluated one at a time before reassembly onto the rack, but no final seal inspection had been performed after reassembly. The operating protocol during on-site use had not explicitly called for extensive verification of the absence of leaks or the traceability of such an inspection. The incident caused no injuries, as personnel had been equipped with the appropriate individual gear. Corrective actions were introduced into the execution of operations related to retesting equipment and their traceability.