During his daily inspection, the production manager observed fumes emanating from one of the masonry 2-hour fire boxes located outside of buildings at a plant manufacturing and packaging swimming pool treatment products. The boxes contained drums (50 kg) filled with sweeping residues and dusts from organic chlorinated products collected from the packaging shops’ environment vacuums. The wastes consisted of highly volatile trichloro-iso-cyanuric acid (TCCA) and derivatives, likely to be contaminated by inorganic materials recovered from the floor or by the ambient humidity. These wastes are normally retreated 2 to 3 times/week depending on the stocks. The employees sprayed down the fire and the manufacturer requested that the establishment next door confine themselves as a preventive measure. The firemen were called and arrived 15 minutes later. It took 10 minutes to bring the accident under control. No abnormal concentration of chlorine was detected in the ambient air. The firefighting water (1.5 m³) was collected in a 150 m³ catchpit.

The contents of a poorly sheltered drum had spontaneously hydrolysed in contact with rainwater, releasing HCl, etc. The wooden pallet supporting 2 residue drums caught fire as a result of the exothermic reaction. The operator reviewed its danger study (scenarios), permanent security of the site was started at night and the dusts will no longer be stocked but treated on a daily basis.