Around 4:30 pm, nitrous vapours were released within a surface treatment company subsequent to an accidental mix involving 20 litres of used paints (including xylene) and 65 litres of sulphonitric acid in a barrel of waste. Some 100 employees had to be evacuated and the emergency rescue team was notified. The site’s energy supply lines (electricity, gas and water) were all shut off. A 200-m safety perimeter was installed and about 30 occupants in 2 dwellings and 5 industries in the vicinity were confined indoors. Fire-fighters diluted the gaseous release using flow-control hoses, and the smoke removal hatches of the affected premises were opened. The barrel containing 25 litres of residual waste was isolated and cooled. Responders left the site around 8 pm. No injuries were reported. Roughly 50 litres of extinction effluent were poured into the storm drain network, given the lack of operable sealing devices.

The use of an unidentified barrel, which technicians assumed to be empty, in the paint workshop for the waste packaging of expired products caused this exothermic reaction. Laboratory staff assigned to prepare the barrel lacked sufficient time to do so and the communication of instructions between this unit and the workshop broke down. Following the accident, the site operator adopted several corrective actions, namely: ban on using barrels recycled in-house for wastes, better contents identification, additional paint shop personnel training, presence of a laboratory staff member when packaging wastes, and improved safety instructions. Plans were also made to revise protocols and employee training in the use of water network plugs.