Around 10:45 am during a polymerisation operation carried out inside a chemical plant, the supply connection on a circuit to grease the packing of the screw stirrer for an autoclave loosened, causing a leak of less than 200 kg of monomer vinyl chloride (MVC). The local MVC alarm in the plant was triggered; personnel were evacuated and confined, while internal response teams placed the device in secure mode and stopped the leak within 15 min. The autoclave was restarted once the connection had been repaired. The operator informed the classified facilities inspectorate and the municipality, in indicating that this incident would give rise to an in-depth analysis and in issuing a press release.