Two workers were asked to change the piping and support of a feed line into an intermediate storage vessel for hydrochloric acid. The explosion occurred when they opened the gas line and started grinding on the support, The flame propagated back into the tank, causing a second explosion inside. The explosion was caused by the unexpected presence of a considerable amount of hydrogen in the tank. According tot the eMARS and ARIA report (see references) , the hydrogen was formed in a reaction of metal powder traces and the hydrochloric acid, and must have accumulated over a period of two months.

Explosion in a food products plant (Seveso classified)The event occurred in the settling cyclone of a hydrogenation reactor of a starch production unit. The process consists in introducing the starch hydrolysate mixture into the reactor with a catalyst (Raney nickel), under agitation and 50 bar of hydrogen at 130C. The reaction lasts three hours, after which hydrogenated mixture is racked and decanted before purification. The explosion occurred during the discharge of the reactor into the settling cyclone.

A fire in a metallurgical plant (classified Seveso)The fire initiated in a acid treatment reactor of a workshop handling cementation of indium . Under normal conditions, the reaction of the process in the tank releases hydrogen. The fire propagated to the plastic components above the tank, causing black smoke released inside the workshop. The origin of the fire were sparks produced by the grinding of metal gratings overhanging the tank.

The event was initiated by the burst of a rupture disc on a reactor during a hydrogenation process. The hydrogenation reaction occurs under pressure in a tank containing 3,000 l of a mixture of ethanol (a flammable and toxic solvent), red hair dye, a catalyst (palladium on carbon) and hydrogen. As a result of the disk rupture and the following tank decompression, decompression, part of the tank content was expelled and landed on the roof of the building.The emergency action consisted in stopping the supply of hydrogen and to purge the tank with nitrogen.

The fire occurred on a flange of a hydrogen supply line to a desulfurization reactor unit of diesel, which leaked and ignited (30 cm flame) The leak was stopped by isolating the part of line affected, by closing the upstream and downstream valves , and shutting down the reactor.

A hydrogen fire occurred in a nuclear power plant outside the controlled area. The leaking point was on a pipe system of the distribution circuit of the gas network (6 bar nominal working pressure). The specific location was a joint on the fire-protection cupboard containing the hydrogen cylinders. The fire started during a repairing intervention on a cupboard nearby, performed by a sub-contractor using a hot surface welding equipment. Internal emergency services isolated and depressurized the pipes, and extinguished the flame.

A hydrogen leak occurs at a gas cylinder storage tank park in a nuclear power plant. Employees locate the origin of the leak on a defective pressure regulator. They isolate the hydrogen release and secure the park. 10 m of gas, the equivalent of one and a half cylinders, escaped.

The fire started in a electrolysis cell. The fire originated from a hydrogen leak in the hydrogen over pressure control system of the cell and an unidentified ignition source. The ARIA report (sew references) calls this control system a "hydrogen guard". The hydrogen leak comes from a lack of water in the guard due to the lack of filling of the guards by the operators and their flushing.The flushing of the hydrogen through the guard was caused by the rise in pressure of the hydrogen line due to the activation of the chlorine burner.

The fire broke out in the acid etching tank of the ferric chloride manufacturing unit of a SEVESO-classified chemical plant. In this tank, the attack reaction of the iron metal with hydrochloric acid in solution is carried out, which results in ferrous chloride and hydrogen. The hydrogen generated is swept away by a large supply air fan to maintain the gaseous sky of the tank below the LFL. A few days after the accident, the operator opened and analysed the tank to determine the origin of the fire.

The event occurred in a university research building dedicated to the study of the take-off of space launchers . An operator gave the alarm during the hydrogen pressure pre-setting phase. he had seen on the video surveillance screen a flame at a pressure regulator on the line located on the walkway above the test hall.