At around 10:00 a.m., chlorine began leaking from the gas line at the compressor suction outside the chlorine storage building of a PVC manufacturing plant just as an emptying operation was commencing. The pair of workers doing the emptying were alerted by the noise created by the leak. They closed the valve to isolate the leak. White vapours were spotted on the section of line upstream of the storage room. As the north-north-east wind was very light, the cloud stayed motionless before heading southward. A neighbouring company, whose workers complained of the smell of chlorine and bleach, informed the plant’s on-call manager and evacuated its staff.

According to the operator, the 3-bar leak lasted for one minute and released 5 kg of chlorine. He indicated that it did not cause irreversible effects outside the plant. The lethal effect limits were not reached.

The leak occurred on a 90° elbow. Localised corrosion was suspected due to the presence of ferric chloride. As this pipe could cause a major accident, it was monitored as part of the industrial facilities modernisation plan (PM2I). When visiting the plant after this event, the inspection authorities for classified facilities found that the inspection reports for the pipes, drawn up as part of the PM2I, were incomplete:

• they did not allow for tracking of thickness measurements made;
• the singularity points of the lines were not clearly identified on the diagrams;
• attack by ferric chloride was not identified.

The inspection authorities recommended that the prefecture issue a formal notification ordering the operator to update its pipe inspection plans.

Unloading operations had been halted for one week prior to the leak because of work in the compressor room. The leak occurred during recommissioning with a non-functional pressure detector (a safeguard). This situation was not included in the safety report.

The operator brought the line back to safe operating condition and scheduled various actions:

• an assessment of the section to determine the leak’s mode of action, confirm the pipe material and update the PM2I monitoring;
• non-destructive testing of the pipe and a look into the possibility of testing with a fluid;
• updating the plant’s on-call procedure;
• creating an incident notification sheet for neighbouring businesses and a news bulletin on the event to be distributed to technicians and on-call staff.

The inspection authorities for classified facilities made the following additional requests:

• verify that the inspection plans for all plant equipment are designed to detect the modes of action of general and localised corrosion;
• update the safety report.