In a foam manufacturing plant for the automotive industry, a mechanical failure caused the spreading of 100 l of TDI (toluene diisocyanate) when starting up a prototype production line. Classified as extremely toxic according to the ‘SEVESO 2’ Directive, the product spread over 18 m² in the retention area connected to the platform. The staff were evacuated. The maintenance team put on SCBA, closed the valve on the 200 l tank of TDI, and spread absorbent products. The product retained in the retention area was eliminated and a specialist company cleaned up the platform. Air measurements were taken using portable analysers to check that the TDI vapours had fully dissipated.

The failure occurred on a booster valve following the accidental closure of a manual valve by a technician. Installed on a low pressure system, this valve was used for maintenance operations. Its closure caused a pressure buildup and breakage of the valve. The operator checked that the production lines had no other systems equipped with such valves that were likely to produce the same type of accident and revised the procedures to be followed in the event of TDI spreading. Pending the results of the assessment and the possible elimination of the valve in question, it was padlocked in open position.