Pollution
Humain
Environnement
Economique

In an upper-tier Seveso-rated plant manufacturing polymers used for water treatment applications, and despite the differentiated storage and packaging zones, a technician assigned the morning shift poured by mistake 1 to 2 kg of sodium hypophosphite classified non-hazardous into a buffer tank containing the combustive fuel ammonium persulfate. These 2 white powder products were difficult to visually distinguish.

The technician pointed out the mistake to both his team leader and workshop technician, who decided to separate the two products as best they could into 2 samples, the first 15 kg of persulfate polluted by the hypophosphite placed into the new plastic drum, and the second between 2 and 3 kg of hypophosphite polluted by persulfate placed in a transparent plastic bag.

A technician working the afternoon shift spilled the drum to empty it at 5:45 pm into a dissolution tank containing 1,100 litres of water. A deflagration inside the drum threw it backwards, fracturing the technician’s arm and burning him from the spattering of product. These projections also slightly injured a 2nd workman operating nearby.

After the explosion, the workshop technician, who was aware of the existence of the 2nd sample of 2-3 kg of hypophosphite polluted by the persulfate, contacted an R&D chemical engineer. The technician seized the plastic bag in order to examine its contents in the presence of the chemical engineer. When returning the bag to its place at 6 pm, the technician was victim of a 2nd deflagration seriously injuring his hands. Spattered contents also burned the engineer on the face and ignited a bag of hypophosphite on an adjacent pallet.

The Second Intervention team snuffed the flames using a fire protection cover. The 6 individuals present in the shop evacuated the premises. External responders removed the 4 injured victims. The bag under this cover was transferred to an isolated zone. The Prefecture and classified facilities inspectorate were duly informed. Three investigations were initiated: one by the firm, the medical insurance office and labour inspection; the 2nd by the classified facilities inspectorate, and the last one by the court which named a legal expert in chemistry.

The site’s Managing Director, when interviewed in the press, stated that “no one could have ever imagined that such a small quantity of product in the can could have exploded”. The operator conducted a study in order to understand the mechanism responsible for these deflagrations. The two chemical products were from then on stored in 2 distinct rooms. The operator issued a press release.

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