At a plastics plant, a nitrogen injection pipe broke at the level of a pyrolysis oven (dichloroethane pyrolysis for producing vinyl chloride). Technicians quickly intervened to shut down the dichloroethane supply line to the oven, yet a loud noise persisted.

The downstream valves were closed and the sprinkling system activated, making it possible to confine the leak to oven contents, which after draining amounted to 2,062 kg of dichloroethane, 41 kg of CVM and 23 kg of HCl. The background detection networks only signalled this leak as the incident was unfolding, once the wind had changed direction.

This pipe rupture was due to internal corrosion of the nitrogen injection pipeline, as a likely consequence of acidic condensation adjacent to the oven wall due to a lack of heat insulation. This incident called into question background detection networks, which under certain wind conditions had become inoperable; doubts were also raised regarding pipe thickness controls by ultrasound.