One Sunday at around 1:20 a.m., a fire started in an open-air cabinet used to store reagents at a hazardous waste treatment plant. Seeing the fire, the CCTV monitoring service alerted the firefighters and remotely opened the gate for them. The operator arrived at the plant. A 50-m cordon was set up around the reagent cabinet. The fire was caused by buckets of aluminium phosphide stored on pallets in the cabinet. The firefighters donned SCBAs and used a thermal imaging camera to examine pallets loaded with phosphide stored at other locations (sorting area and mineral cabinet).
They smothered the burning waste with 3 t of diatomaceous earth. The fire produced 10 t of waste (combustion of the substances stored in the reagent cabinet). This burnt waste was placed in ninety-four 30-l metal buckets and fifty-seven 200-l metal drums. A total of 200 l of paraffin oil was used to neutralise the still-reacting residues.
Thirteen pallets of inert aluminium phosphide strips packed in buckets (18 l) had been received on Friday afternoon. An odour test had been conducted on the incoming pallets (no odour was detected), but the buckets had not been opened due to the hazardous nature of the substance. All the storage facilities (11 pallets in the reagent cabinet, one pallet in the minerals cabinet and one pallet in the sorting area) were checked with a thermal imaging camera later that evening. Nothing unusual was found.
However, the strips were not been completely inert. The reaction occurred because they were packaged in buckets instead of in individual sealed bags that had been emptied of all air. The phosphine gas produced by this reaction caused the pressure in the buckets to rise. The buckets then burst and the gas ignited on contact with the open air.
Since the accident, the operator has asked its customers (waste suppliers) to place this waste in suitable containers and/or requires them to have it checked by a chemical engineer prior to delivery to the plant. It has made its workers aware of the need to ensure that these instructions are followed when accepting waste.
