In one of the buildings at a vehicle manufacturing plant, chlorinated vapours were released around noon following the accidental transfer of 100 litres of ferric chloride (FeCl3) in a tank containing 1,200 litres of 96% sulphuric acid (H2SO4). The accident occurred during delivery of 800 litres of FeCl3 by a chemical products supplier. The lorry driver erroneously connected the ferric chloride container to the H2SO4 transfer outfall, despite the clearly visible marking, during the momentary absence of the plant foreman certified to perform this task (called away to prepare rinsing the water pipe of the supplier’s couplings). The 4 individuals present at the scene (3 plant employees and the driver) were evacuated and examined by the company physician. First responders measured 0.2 ppm of chlorine and 1 ppm of hydrogen chloride in the building; no impacts were recorded outside the plant. Fire-fighters transferred tank contents into a buffer reservoir while awaiting disposal. Subsequent to this accident, the operator posted the detailed transfer protocol, stressing that the connection to the fixed storage facility was to be performed by a staff member; held a training session for plant personnel on these specific unloading operations; requested the supplier provide training for its drivers; and introduced locking plugs and distinct colour codes for each product.