Pollution
Humain
Environnement
Economique

At 3:43 p.m., a phosgene leak occurred in a confined production unit during the start-up phase of a chemical plant. Ongoing production operations were stopped and the operator initiated the emergency response plan. The plant’s internal emergency services secured the area and triggered the gas alert. Twenty-five people were confined for 3 hours and 15 minutes. The technicians managed to locate and isolate the leak, and the emergency response plan was subsequently lifted at around 7 p.m. The operator issued a press release.

It was estimated that between 37 and 50 kg of phosgene had been released into the containment area and less than 1 kg into the atmosphere. Two persons were affected by phosgene inhalation and treated by the infirmary. The economic consequences of the incident were estimated at 50 k€.

During the start-up phase, a leak had been identified on the pressure sensor on the discharge side of a high-pressure phosgene pump. The leak is believed to have resulted from incorrect tightening. The operator emptied the phosgene line to work on this sensor, and the phosgene pump was stopped. A nitrogen hose was connected to the pump’s intake to complete the supply manoeuvre by blowing; the nitrogen utility valve was opened although the line was not completely decompressed. The operator then received the information from the control room and closed the valve again, but only partially. As no check valve had been installed, phosgene returned into the nitrogen network in the workshop. All the safety devices in the workshop had functioned correctly, which allowed the release to be limited.

The check valve between the phosgene and nitrogen networks had been leaking and had been removed pending replacement with another technology. This modification had not been performed in accordance with the change management procedure and therefore had not been followed up.

The operator implemented the following corrective actions following the event:

  • replacement of the leaking pressure sensor,
  • clean-up of the workshop’s nitrogen network,
  • installation of a non-return valve on the nitrogen network’s utility intake,
  • modification of the way the nitrogen hose is attached to the pump to limit the possibility of opening the network before decompression is completed,
  • improvement of the procedure for preparing the phosgene line preparation using a nitrogen blowing process,
  • update of change management feedback.