A release of chlorine occurred at around 2:00 p.m. in one of the units of a cheese factory. The 12 people present at the unit were sickened, but not taken to hospital. The entire site of 48 employees was evacuated. A crisis management procedure was implemented at 3:00 p.m. A PR firm was hired to assist management in dealing with the situation and to take care of external communication. Two local journalists working with this firm wrote stories about the incident. Two appeared in newspapers the next day.

Firefighters arrived wearing SCBAs. They immediately saw that the fumes were coming from a pipe, which they flushed. The site’s ripening chambers and offices were closed from 2:30 p.m. to 5:00 p.m. Its cutting unit, the source of the fumes, was closed from 2:30 p.m. to 9:00 p.m. To avoid disruption of supply to customers, loading of the semi-trailer of finished products was postponed to the following days.

The accident was caused by two cleaning operations that were performed at the same time using two incompatible products. First, the quality department asked a technician to descale the sink in the cutting unit’s depalletiser room. He sprayed it with 100 ml of undiluted acid and left it to work. Then, the same department asked another technician to clean and disinfect the drainage sewer at the room’s entrance. This technician used 2 l of solution of 33% bleach diluted to 50%. When both technicians were finished, they drained both the acid and the bleach to two separate pipes that actually joined together. After a certain contact time, the incompatible chemicals reacted, releasing toxic chlorine gas.

The operator took the following measures:

• actions to train and raise employees’ awareness of the risks of chemicals and the rules on their use (concentrations, etc.); ;
• the use of already diluted chlorine solutions;
• it specified good cleaning practices in the cleaning procedures;
• when cleaning operations are performed, water is to be kept flowing to prevent very high concentrations of potentially incompatible chemicals mixing together;
• it collected the technical data sheets and MSDS of the products in question.

A chemical risk audit, carried out on 11 May, was also added to the factory’s safety action plan. The employees were informed and made aware of the analysis of the accident’s causes and the plant’s alert procedures were assessed (crisis management and alert procedure).