In the stripping workshop of a firm specialised in the stamping and machining of parts made of an aluminium and titanium alloy, a large quantity of nitrous vapours were released in the 3,500-litre cold-working, fluonitric acid bath (containing 5% HNO3 and 15% HF at 40%). Fire-fighters with a chemical emergency squad were called to pump 1,900 litres of the bath, whose temperature kept increasing to 102°C; at this point, they stopped pumping in order to cool the remaining bath by means of dilution with water. At 50°C, they were able to complete draining of the tank 5½ hours after the incident outbreak. The plant’s workforce of some 100 was quickly evacuated and 3 workshop technicians, who had taken ill, were hospitalised for observation. A 1-km safety perimeter was set up: 600 employees with a neighbouring plant located downwind were also evacuated, while traffic was blocked for 6 hours on the motorway running near the plant. An incident occurring on one of the 2 hoists for a basket containing 4 aluminium parts (length = 2.5 m, 250 kg/unit) prevented the basket from being lifted outside the treatment tank, thereby triggering a chemical reaction caused by extended metal/acid contact. A judicial investigation was initiated and the Classified Facilities Inspectorate requested the operator to submit an accident analysis report.

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