A release of hydrochloric acid vapours occurred during cleaning of a 50-m³ tank that had contained sulphur chloride. The water introduced by site technicians reacted with the sludge at the tank bottom (approx. 30-mm thick), composed for 50% of sulphur monochloride. The cloud of hydrochloric acid and sulphur dioxide drifted away from the plant; 24 students at a nearby high school reported feeling ill and were hospitalised one day for observation. This accident, due to an inappropriate operating protocol, generated widespread media coverage.