Hydrochloric acid fumes were released at around 8:30 a.m. at an incinerator while a 1000 l IBC was being emptied of 33% hydrochloric acid. The driver noticed the fumes emanating from the roof and stopped the transfer, leaving 500 l inside the IBC. The site’s personnel sought safety. The wind pushed the fumes towards the nearby wastewater treatment plant, where five employees were affected and had to be taken to hospital (they were discharged the same day).

The haulier’s analysis of the incident revealed that the stainless steel IBC in question was improperly labelled and contained concentrated sulphuric acid (98% H2SO4). This is why incompatible chemicals were mixed together in the site’s hydrochloric acid tank and released irritating fumes that damaged nearby electronic equipment.

The root cause of accident occurred on the chemical site that sent the shipment and was due to a combination of operational and verification errors (organisational factor). On the site, IBC have two labels: one on the front and one on the rear. On the day the IBC in question was filled, hydrochloric acid and sulphuric acid were filled on the same grating line and a human error led to the label between two IBCs being swapped. As a result, the IBC was labelled ‘HCl’ on its front and ‘H2SO4’ on its rear. Because the forklift operator loads IBCs from the rear (the side with the correct label), he was completely unaware of the error. The driver who transported the two types of IBC did not know that HCl labels are not placed on stainless steel containers (HCl is incompatible with stainless steel). He relied on the labels as indicated in the instructions, and then the incident described above occurred.

The site is revising its unloading agreements with its supplier and looking into the possibility of equipping its employees with combination dust and acid respirators. The chemical site’s procedures now include checking the front and rear labels of IBCs while they are being loaded. From now on, only one type of chemical will be filled at a time on its filling lines. Safety memos remind technicians to make sure that old labels are removed from both sides of containers before new ones are affixed. Drivers are reminded to check the contents of containers before unloading them at consignees’ sites. Lastly, drivers are also made more aware of incompatibilities between chemicals and materials.