The safety cabinet with compressed hydrogen was located in a laboratory and used to supply hydrogen to an experimental facility. The safety cabinet was equipped with exhaust extraction. Due to a leak, technical assistance had been requested from the fire department. The head of laboratory shut off the electrical supply to the laboratory. Measurements showed that there was no potentially explosive atmosphere in the laboratory room.

The event occurred at manhole cover of a of a pilot plant reactor where hydrogenation had been performed in a hydrochloric aqueous solution. The reactor had been flushed three times with nitrogen (i.e. nitrogen injecting at 3.2 bars and then relieving). An employee opened the manhole cover of the reactor to take a sample of the reagent. . After opening it, a minor detonation occurred.According to the DECHEMA database, the investigations found out these following causes:1.

The incident occurred in an electrostatic filtration unit. When flushing with air during the start-up phase of a sulphonation plant, an explosion occurred in the upper partof the electrostatic filtration plant (electrostatic precipitators). The most serious effects of the pressure wave were the violent detachment of the manhole cover of the plant, rupture of two insulating supports and deformation of the gas distributor plate.[DECHEMA incident database, event no. 05/ 2001]

The event occurred in the continuous casting of hot metallic melt of the plant.Cooling water leaked through a crack in the cooling water inlet pipe of a secondary cooling line and directly into the hot melt (temperature > 1500 C). This resulted in the formation of hydrogen which ignited on the hot surface. The pipe in question had been in operation for a prolonged period. The material analyses of the component showed that the rupture occurred as a consequence of fatigue. The annual visual inspection had revealed no signs of imminent failure.