At 6:50 a.m., orange-coloured nitrous fumes were released during routine cleaning in a biscuit manufacturing plant. The nickel-plated brass rings on one of the lines were being cleaned per the standard protocol. After cleaning and rinsing, the rings did not appear to be sufficiently clean, so they were placed in a bucket containing a mixture of water and a strong acid composed of nitric acid (45%) and phosphoric acid. Staff then introduced the rings from a second line, which had not been cleaned according to the standard protocol, into a second bucket containing the same mixture. The release of orange fumes occurred just a few minutes later. The personnel evacuated the site. The emergency services examined eight people who had been affected or disturbed by the event. Production was stopped between 6:50 and 10:20 a.m.

The operator used a strong acid that is manually dosed on site, and the solution was thus weakly diluted and not specified in the standard protocol for cleaning the diffusers. This chemical product is accessible in a storeroom for which the operators have the code.

The facility operator has implemented the following actions:

• the crews are reminded that the cleaning protocols are mandatory and that manual dosing is prohibited;
• the safety data sheets (SDS) of all cleaning products are analysed to identify powerful substances and identified incompatibilities;
• the organisation of a chemical risk training module for all personnel and in-depth training for operators at specific workstations;
• reinforcement of the chemical risk section of the safety indoctrination module;
• installation of a locked storeroom for acidic chemical products;
• review of the cleaning frequency of the diffusers and include a downgraded version of the standard protocol if the cleaning results are unsatisfactory.