In a brewery, the deliveryman transporting 2 tonnes of hydrochloric acid (HCl) connected the tank truck to the filling inlet of the sulphuric acid (H2SO4) tank, next to that of the HCl tank in the absence of a factory staff. Immediately after the pump was started, a cloud was formed and released via the blow off of the tank. The transfer was stopped after verification, but 500 litres of HCl has already been transferred to 1,500 litres of H2SO4. The staff from the buildings impacted by the cloud was evacuated. The zone was marked and entry prohibited. The tank was cooled with water until the arrival of a team from the transport company that transferred the contents into a tank pre-filled with 10 m³ of water, slowing down and subsequently stopping the exothermic reaction. A CMIC chemical emergency squad measured chlorine concentrations to be 0.5 ppm. An initial analysis of the causes showed the absence of a formal transfer procedure that required a factory staff to be present for all transfer operations. Moreover, the deliveryman who normally delivered H2SO4 was filling in for the delivery of HCl on that particular day. The filling inlets of the two acids were close to each other and were protected by the same locked cabinet.