A tank of hydrochloric acid (33% HCl, which is toxic and corrosive) located in a storage area at a chemical plant overflowed for several minutes while it was being filled. The 50 l of hydrochloric acid that was spilt was collected on the containment platform.

According to the procedure, a technician should enter into a computer program the amount of acid to be transferred and stay nearby in case of an incident. The overfilling was caused by three things: an unreliable high-level sensor, technician error in programming the meter (29 t instead of 25 t was entered) and inadequate monitoring at the end of loading. The technician, occupied by other tasks, failed to stay near the meter as he should have in order to monitor that filling was automatically shut off by either the program or the high-level sensor (which was faulty at the time). The operator implemented actions to increase awareness — of the operator and of the entire crew in charge of filling — about the importance of following instructions when transferring chemicals. In addition, it now requires that the level sensor (replaced with a new one of different technology) be tested before the first loading of each day to confirm that it operates correctly. This will also ensure that employees will always bear in mind the correct procedure to follow.