At 13h45, a leak of chorine occurred in a chemical company producing titanium oxyde (Ti0) after a failure of the public power supply.

The plant was operating under standard conditions; the gas produced by the chemical reaction (a mixture of chlorine, nitrogen, hydrochloric acid and carbon dioxide) are separated. In case of system failure, the gas is directed to the snake scrub system, a chlorine destruction unit. The gas is directed to this system via a vacuum, created by two ventilators. At 13h40, a short power failure of the public power supply was followed by a power failure of the plant emergency power supply. Thus, the 2 ventilators were blocked and about 120 kg of chlorine gas were released at ground level because the valve to the chimney is closed during a power failure (poor safety design).

The emission went unnoticed and no gas alarm was sounded because the chlorine went underneath the chlorine detection system located at the height of 3 m. Anyway, the gas detection system might also have been impacted by the power failure…

At a waste-disposal company situated on the nearby premises, 32 employees of a building company working on the construction of a new chemical oven were injured by the chlorine cloud and sounded the alarm (phone call to the emitting company). On top that, the power failure created an overburdening of the telephone network and it took the company about 8 minutes to inform the Police Alarm Centre via the Chemical incident network. The following evacuation process was chaotic; the employees were sent to the hospital for medical check-ups.

The operator reviewed the plant to prevent dangerous situations following a total loss of power, the steam driven emergency generator was completed with a diesel one, the gas detection system has been significantly improved through extra detection systems (redundancy) and a link with neighbouring company and the alarm procedures have been improved.