At 6:57 h, the failure of a pressurised system caused the release of 0.5 t of hydrogen chloride (HCl) to the atmosphere. A visible cloud drifted off site towards residential area. Establishment shut-down process and about 70 fire-fighters used water sprays to help knock down the HCL cloud. Several hundred people were instructed to shelter indoors for more than 2 hours, the traffic on nearby motorway and adjacent major ring-road was stopped for 3 h. Ten people off site reported to hospital with eye irritation; none serious.

Bellows ruptured under pressure (4 bar /145°C) due to internal corrosion after less than 12 months use. They were made of stainless steel, with PTFE-lined bellows (12″ diameter, approx 10″ across) and situated in the pipework between an acid droplet separator and an HCL desorption column. The cause of the accelerated corrosion could be a design specification error or wrong spec bellows fitted or bellows not properly maintained.