At around 3:40 p.m., a fire broke out on a 1000 l drum of hydrogen peroxide stored near an effluent treatment facility at a chemical plant. The plant’s emergency services extinguished the fire using powder extinguishers and then cooled down the drum with a water hose. The mixture of hydrogen peroxide and firewater meant that the effluent treatment system had to be temporarily shut down, but no discharges occurred offsite.

The operator looked into the possible causes of the fire, but could not establish with certainty what the exact cause was (all the evidence had been destroyed by the fire). He found that the most likely causes were:

• A rise in the drum’s pressure or a leak. The hydrogen peroxide flowed into the drum’s spill tray, wetting leaves in the tray and producing an exothermic reaction that ignited them. Usually, this spill tray contains water in order to dilute any spills. However, it was dry as a bone from the hot weather.
• The pressure inside the drum rose, causing the venting valve to spray out hydrogen peroxide onto the wooden pallet of empty drums next to the spill tray and igniting it in an exothermic reaction.

The drum was used to store the dregs from containers used to supply the unit with hydrogen peroxide. It may therefore have contained pollutants that had built up during transfer operations (effect on the product’s stability) or showed signs of wear (valve, plug).

The hot temperatures that had prevailed for several days may also have promoted the hydrogen peroxide’s exothermic decomposition.