During a delivery of 2 semi-tanks filled (one with sodium hypochlorite solution, the other with hydrochloric acid), an explosion took place and chlorinated vapours were released. As the labels of the semi-tanks had been interchanged, the operator filled the tank for hydrochloric acid with 100 liters of sodium hypochlorite. The venting valve of the stationary tank was ripped off due to over pressure. The local authorities were called. An helicopter is used for aerial control. A warning message by radio is broadcast. 34 persons are hospitalised by release. A specialised company fetched the contaminated hydrochloric acid. The following conclusions were drawn for prevent recurrence of similar accidents :

• installation of a pH controlled safety valve on the stationary tank of the customer;
• forbidden simultaneous transport of chemicals.